int[] a = ...; static bool greater(int a, int b) { return a > b; } sort!(greater)(a); // predicate as alias sort!("a > b")(a); // predicate as string // (no ambiguity with array name) sort(a); // no predicate, "a < b" is implicit
Function Name | Description |
---|---|
Searching | |
all | all!"a > 0"([1, 2, 3, 4]) returns true because all elements are positive |
any | any!"a > 0"([1, 2, -3, -4]) returns true because at least one element is positive |
balancedParens | balancedParens("((1 + 1) / 2)") returns true because the string has balanced parentheses. |
boyerMooreFinder | find("hello world", boyerMooreFinder("or")) returns "orld" using the Boyer-Moore algorithm . |
canFind | canFind("hello world", "or") returns true. |
count | Counts elements that are equal to a specified value or satisfy a predicate. count([1, 2, 1], 1) returns 2 and count!"a < 0"([1, -3, 0]) returns 1. |
countUntil | countUntil(a, b) returns the number of steps taken in a to reach b; for example, countUntil("hello!", "o") returns 4. |
endsWith | endsWith("rocks", "ks") returns true. |
find | find("hello world", "or") returns "orld" using linear search. (For binary search refer to std.range.sortedRange.) |
findAdjacent | findAdjacent([1, 2, 3, 3, 4]) returns the subrange starting with two equal adjacent elements, i.e. [3, 3, 4]. |
findAmong | findAmong("abcd", "qcx") returns "cd" because 'c' is among "qcx". |
findSkip | If a = "abcde", then findSkip(a, "x") returns false and leaves a unchanged, whereas findSkip(a, 'c') advances a to "cde" and returns true. |
findSplit | findSplit("abcdefg", "de") returns the three ranges "abc", "de", and "fg". |
findSplitAfter | findSplitAfter("abcdefg", "de") returns the two ranges "abcde" and "fg". |
findSplitBefore | findSplitBefore("abcdefg", "de") returns the two ranges "abc" and "defg". |
minCount | minCount([2, 1, 1, 4, 1]) returns tuple(1, 3). |
minPos | minPos([2, 3, 1, 3, 4, 1]) returns the subrange [1, 3, 4, 1], i.e., positions the range at the first occurrence of its minimal element. |
skipOver | Assume a = "blah". Then skipOver(a, "bi") leaves a unchanged and returns false, whereas skipOver(a, "bl") advances a to refer to "ah" and returns true. |
startsWith | startsWith("hello, world", "hello") returns true. |
until | Lazily iterates a range until a specific value is found. |
Comparison | |
cmp | cmp("abc", "abcd") is -1, cmp("abc", "aba") is 1, and cmp("abc", "abc") is 0. |
equal | Compares ranges for element-by-element equality, e.g. equal([1, 2, 3], [1.0, 2.0, 3.0]) returns true. |
levenshteinDistance | levenshteinDistance("kitten", "sitting") returns 3 by using the Levenshtein distance algorithm . |
levenshteinDistanceAndPath | levenshteinDistanceAndPath("kitten", "sitting") returns tuple(3, "snnnsni") by using the Levenshtein distance algorithm . |
max | max(3, 4, 2) returns 4. |
min | min(3, 4, 2) returns 2. |
mismatch | mismatch("oh hi", "ohayo") returns tuple(" hi", "ayo"). |
Iteration | |
filter | filter!"a > 0"([1, -1, 2, 0, -3]) iterates over elements 1 and 2. |
filterBidirectional | Similar to filter, but also provides back and popBack at a small increase in cost. |
group | group([5, 2, 2, 3, 3]) returns a range containing the tuples tuple(5, 1), tuple(2, 2), and tuple(3, 2). |
joiner | joiner(["hello", "world!"], ";") returns a range that iterates over the characters "hello; world!". No new string is created - the existing inputs are iterated. |
map | map!"2 * a"([1, 2, 3]) lazily returns a range with the numbers 2, 4, 6. |
reduce | reduce!"a + b"([1, 2, 3, 4]) returns 10. |
splitter | Lazily splits a range by a separator. |
uniq | Iterates over the unique elements in a range, which is assumed sorted. |
Sorting | |
completeSort | If a = [10, 20, 30] and b = [40, 6, 15], then completeSort(a, b) leaves a = [6, 10, 15] and b = [20, 30, 40]. The range a must be sorted prior to the call, and as a result the combination std.range.chain(a, b) is sorted. |
isPartitioned | isPartitioned!"a < 0"([-1, -2, 1, 0, 2]) returns true because the predicate is true for a portion of the range and false afterwards. |
isSorted | isSorted([1, 1, 2, 3]) returns true. |
makeIndex | Creates a separate index for a range. |
nextPermutation | Computes the next lexicographically greater permutation of a range in-place. |
nextEvenPermutation | Computes the next lexicographically greater even permutation of a range in-place. |
partialSort | If a = [5, 4, 3, 2, 1], then partialSort(a, 3) leaves a[0 .. 3] = [1, 2, 3]. The other elements of a are left in an unspecified order. |
partition | Partitions a range according to a predicate. |
schwartzSort | Sorts with the help of the Schwartzian transform . |
sort | Sorts. |
topN | Separates the top elements in a range. |
topNCopy | Copies out the top elements of a range. |
Set operations | |
cartesianProduct | Computes Cartesian product of two ranges. |
largestPartialIntersection | Copies out the values that occur most frequently in a range of ranges. |
largestPartialIntersectionWeighted | Copies out the values that occur most frequently (multiplied by per-value weights) in a range of ranges. |
nWayUnion | Computes the union of a set of sets implemented as a range of sorted ranges. |
setDifference | Lazily computes the set difference of two or more sorted ranges. |
setIntersection | Lazily computes the intersection of two or more sorted ranges. |
setSymmetricDifference | Lazily computes the symmetric set difference of two or more sorted ranges. |
setUnion | Lazily computes the set union of two or more sorted ranges. |
Mutation | |
bringToFront | If a = [1, 2, 3] and b = [4, 5, 6, 7], bringToFront(a, b) leaves a = [4, 5, 6] and b = [7, 1, 2, 3]. |
copy | Copies a range to another. If a = [1, 2, 3] and b = new int[5], then copy(a, b) leaves b = [1, 2, 3, 0, 0] and returns b[3 .. $]. |
fill | Fills a range with a pattern, e.g., if a = new int[3], then fill(a, 4) leaves a = [4, 4, 4] and fill(a, [3, 4]) leaves a = [3, 4, 3]. |
initializeAll | If a = [1.2, 3.4], then initializeAll(a) leaves a = [double.init, double.init]. |
move | move(a, b) moves a into b. move(a) reads a destructively. |
moveAll | Moves all elements from one range to another. |
moveSome | Moves as many elements as possible from one range to another. |
reverse | If a = [1, 2, 3], reverse(a) changes it to [3, 2, 1]. |
strip | Strips all leading and trailing elements equal to a value, or that satisfy a predicate. If a = [1, 1, 0, 1, 1], then strip(a, 1) and strip!(e => e == 1)(a) returns [0]. |
stripLeft | Strips all leading elements equal to a value, or that satisfy a predicate. If a = [1, 1, 0, 1, 1], then stripLeft(a, 1) and stripLeft!(e => e == 1)(a) returns [0, 1, 1]. |
stripRight | Strips all trailing elements equal to a value, or that satisfy a predicate. If a = [1, 1, 0, 1, 1], then stripRight(a, 1) and stripRight!(e => e == 1)(a) returns [1, 1, 0]. |
swap | Swaps two values. |
swapRanges | Swaps all elements of two ranges. |
uninitializedFill | Fills a range (assumed uninitialized) with a value. |
auto map(Range)(Range r) if (isInputRange!(Unqual!Range));
Implements the homonym function (also known as transform) present in many languages of functional flavor. The call map!(fun)(range) returns a range of which elements are obtained by applying fun(x) left to right for all x in range. The original ranges are not changed. Evaluation is done lazily.
int[] arr1 = [ 1, 2, 3, 4 ]; int[] arr2 = [ 5, 6 ]; auto squares = map!(a => a * a)(chain(arr1, arr2)); assert(equal(squares, [ 1, 4, 9, 16, 25, 36 ]));
auto arr1 = [ 1, 2, 3, 4 ]; foreach (e; map!("a + a", "a * a")(arr1)) { writeln(e[0], " ", e[1]); }
alias map!(to!string) stringize; assert(equal(stringize([ 1, 2, 3, 4 ]), [ "1", "2", "3", "4" ]));
auto reduce(Args...)(Args args) if (Args.length > 0 && Args.length <= 2 && isIterable!(Args[$ - 1]));
Implements the homonym function (also known as accumulate, compress, inject, or foldl) present in various programming
languages of functional flavor. The call reduce!(fun)(seed,
range) first assigns seed to an internal variable result,
also called the accumulator. Then, for each element x in range, result = fun(result, x) gets evaluated. Finally, result is returned. The one-argument version reduce!(fun)(range)
works similarly, but it uses the first element of the range as the
seed (the range must be non-empty).
Many aggregate range operations turn out to be solved with reduce
quickly and easily. The example below illustrates reduce's
remarkable power and flexibility.
int[] arr = [ 1, 2, 3, 4, 5 ]; // Sum all elements auto sum = reduce!((a,b) => a + b)(0, arr); assert(sum == 15); // Sum again, using a string predicate with "a" and "b" sum = reduce!"a + b"(0, arr); assert(sum == 15); // Compute the maximum of all elements auto largest = reduce!(max)(arr); assert(largest == 5); // Max again, but with Uniform Function Call Syntax (UFCS) largest = arr.reduce!(max); assert(largest == 5); // Compute the number of odd elements auto odds = reduce!((a,b) => a + (b & 1))(0, arr); assert(odds == 3); // Compute the sum of squares auto ssquares = reduce!((a,b) => a + b * b)(0, arr); assert(ssquares == 55); // Chain multiple ranges into seed int[] a = [ 3, 4 ]; int[] b = [ 100 ]; auto r = reduce!("a + b")(chain(a, b)); assert(r == 107); // Mixing convertible types is fair game, too double[] c = [ 2.5, 3.0 ]; auto r1 = reduce!("a + b")(chain(a, b, c)); assert(approxEqual(r1, 112.5)); // To minimize nesting of parentheses, Uniform Function Call Syntax can be used auto r2 = chain(a, b, c).reduce!("a + b"); assert(approxEqual(r2, 112.5));
double[] a = [ 3.0, 4, 7, 11, 3, 2, 5 ]; // Compute minimum and maximum in one pass auto r = reduce!(min, max)(a); // The type of r is Tuple!(int, int) assert(approxEqual(r[0], 2)); // minimum assert(approxEqual(r[1], 11)); // maximum // Compute sum and sum of squares in one pass r = reduce!("a + b", "a + b * b")(tuple(0.0, 0.0), a); assert(approxEqual(r[0], 35)); // sum assert(approxEqual(r[1], 233)); // sum of squares // Compute average and standard deviation from the above auto avg = r[0] / a.length; auto stdev = sqrt(r[1] / a.length - avg * avg);
Fills range with a filler.
int[] a = [ 1, 2, 3, 4 ]; fill(a, 5); assert(a == [ 5, 5, 5, 5 ]);
Fills range with a pattern copied from filler. The length of range does not have to be a multiple of the length of filler. If filler is empty, an exception is thrown.
int[] a = [ 1, 2, 3, 4, 5 ]; int[] b = [ 8, 9 ]; fill(a, b); assert(a == [ 8, 9, 8, 9, 8 ]);
Fills a range with a value. Assumes that the range does not currently contain meaningful content. This is of interest for structs that define copy constructors (for all other types, fill and uninitializedFill are equivalent).
uninitializedFill will only operate on ranges that expose references to its members and have assignable elements.
struct S { ... } S[] s = (cast(S*) malloc(5 * S.sizeof))[0 .. 5]; uninitializedFill(s, 42); assert(s == [ 42, 42, 42, 42, 42 ]);
Initializes all elements of a range with their .init value. Assumes that the range does not currently contain meaningful content.
initializeAll will operate on ranges that expose references to its members and have assignable elements, as well as on (mutable) strings.
struct S { ... } S[] s = (cast(S*) malloc(5 * S.sizeof))[0 .. 5]; initializeAll(s); assert(s == [ 0, 0, 0, 0, 0 ]);
auto filter(Range)(Range rs) if (isInputRange!(Unqual!Range));
Implements the homonym function present in various programming languages of functional flavor. The call filter!(predicate)(range) returns a new range only containing elements x in range for which predicate(x) is true.
int[] arr = [ 1, 2, 3, 4, 5 ]; // Sum all elements auto small = filter!(a => a < 3)(arr); assert(equal(small, [ 1, 2 ])); // Sum again, but with Uniform Function Call Syntax (UFCS) auto sum = arr.filter!(a => a < 3); assert(equal(sum, [ 1, 2 ])); // In combination with chain() to span multiple ranges int[] a = [ 3, -2, 400 ]; int[] b = [ 100, -101, 102 ]; auto r = chain(a, b).filter!(a => a > 0); assert(equal(r, [ 3, 400, 100, 102 ])); // Mixing convertible types is fair game, too double[] c = [ 2.5, 3.0 ]; auto r1 = chain(c, a, b).filter!(a => cast(int) a != a); assert(approxEqual(r1, [ 2.5 ]));
auto filterBidirectional(Range)(Range r) if (isBidirectionalRange!(Unqual!Range));
Similar to filter, except it defines a bidirectional range. There is a speed disadvantage - the constructor spends time finding the last element in the range that satisfies the filtering condition (in addition to finding the first one). The advantage is that the filtered range can be spanned from both directions. Also, std.range.retro can be applied against the filtered range.
int[] arr = [ 1, 2, 3, 4, 5 ]; auto small = filterBidirectional!("a < 3")(arr); assert(small.back == 2); assert(equal(small, [ 1, 2 ])); assert(equal(retro(small), [ 2, 1 ])); // In combination with chain() to span multiple ranges int[] a = [ 3, -2, 400 ]; int[] b = [ 100, -101, 102 ]; auto r = filterBidirectional!("a > 0")(chain(a, b)); assert(r.back == 102);
Moves source into target via a destructive copy. Specifically:
For each element a in src and each element b in tgt in lockstep in increasing order, calls move(a, b). Returns the leftover portion of tgt. Throws an exeption if there is not enough room in tgt to acommodate all of src.
For each element a in src and each element b in tgt in lockstep in increasing order, calls move(a, b). Stops when either src or tgt have been exhausted. Returns the leftover portions of the two ranges.
Swaps lhs and rhs. See also std.exception.pointsTo.
Forwards function arguments with saving ref-ness.
int foo(int n) { return 1; } int foo(ref int n) { return 2; } int bar()(auto ref int x) { return foo(forward!x); } assert(bar(1) == 1); int i; assert(bar(i) == 2);
void foo(int n, ref string s) { s = null; foreach (i; 0..n) s ~= "Hello"; } // forwards all arguments which are bound to parameter tuple void bar(Args...)(auto ref Args args) { return foo(forward!args); } // forwards all arguments with swapping order void baz(Args...)(auto ref Args args) { return foo(forward!args[$/2..$], forward!args[0..$/2]); } string s; bar(1, s); assert(s == "Hello"); baz(s, 2); assert(s == "HelloHello");
Splits a range using an element as a separator. This can be used with any narrow string type or sliceable range type, but is most popular with string types.
Two adjacent separators are considered to surround an empty element in
the split range.
If the empty range is given, the result is a range with one empty
element. If a range with one separator is given, the result is a range
with two empty elements.
assert(equal(splitter("hello world", ' '), [ "hello", "", "world" ])); int[] a = [ 1, 2, 0, 0, 3, 0, 4, 5, 0 ]; int[][] w = [ [1, 2], [], [3], [4, 5] ]; assert(equal(splitter(a, 0), w)); a = null; assert(equal(splitter(a, 0), [ (int[]).init ])); a = [ 0 ]; assert(equal(splitter(a, 0), [ (int[]).init, (int[]).init ])); a = [ 0, 1 ]; assert(equal(splitter(a, 0), [ [], [1] ]));
Splits a range using another range as a separator. This can be used with any narrow string type or sliceable range type, but is most popular with string types.
Lazily joins a range of ranges with a separator. The separator itself is a range. If you do not provide a separator, then the ranges are joined directly without anything in between them.
assert(equal(joiner([""], "xyz"), "")); assert(equal(joiner(["", ""], "xyz"), "xyz")); assert(equal(joiner(["", "abc"], "xyz"), "xyzabc")); assert(equal(joiner(["abc", ""], "xyz"), "abcxyz")); assert(equal(joiner(["abc", "def"], "xyz"), "abcxyzdef")); assert(equal(joiner(["Mary", "has", "a", "little", "lamb"], "..."), "Mary...has...a...little...lamb")); assert(equal(joiner(["abc", "def"]), "abcdef"));
Iterates unique consecutive elements of the given range (functionality akin to the uniq system utility). Equivalence of elements is assessed by using the predicate pred, by default "a == b". If the given range is bidirectional, uniq also yields a bidirectional range.
int[] arr = [ 1, 2, 2, 2, 2, 3, 4, 4, 4, 5 ]; assert(equal(uniq(arr), [ 1, 2, 3, 4, 5 ][]));
Similarly to uniq, group iterates unique consecutive elements of the given range. The element type is Tuple!(ElementType!R, uint) because it includes the count of equivalent elements seen. Equivalence of elements is assessed by using the predicate pred, by default "a == b".
Group is an input range if R is an input range, and a forward range in all other cases.
int[] arr = [ 1, 2, 2, 2, 2, 3, 4, 4, 4, 5 ]; assert(equal(group(arr), [ tuple(1, 1u), tuple(2, 4u), tuple(3, 1u), tuple(4, 3u), tuple(5, 1u) ][]));
Finds an individual element in an input range. Elements of haystack are compared with needle by using predicate pred. Performs Ο(walkLength(haystack)) evaluations of pred. See also STL's find.
To find the last occurence of needle in haystack, call find(retro(haystack), needle). See also std.range.retro.
R haystack | The range searched in. |
E needle | The element searched for. |
assert(find("hello, world", ',') == ", world"); assert(find([1, 2, 3, 5], 4) == []); assert(find(SList!int(1, 2, 3, 4, 5)[], 4) == SList!int(4, 5)[]); assert(find!"a > b"([1, 2, 3, 5], 2) == [3, 5]); auto a = [ 1, 2, 3 ]; assert(find(a, 5).empty); // not found assert(!find(a, 2).empty); // found // Case-insensitive find of a string string[] s = [ "Hello", "world", "!" ]; assert(!find!("toLower(a) == b")(s, "hello").empty);
Finds a forward range in another. Elements are compared for equality. Performs Ο(walkLength(haystack) * walkLength(needle)) comparisons in the worst case. Specializations taking advantage of bidirectional or random access (where present) may accelerate search depending on the statistics of the two ranges' content.
R1 haystack | The range searched in. |
R2 needle | The range searched for. |
assert(find("hello, world", "World").empty); assert(find("hello, world", "wo") == "world"); assert(find([1, 2, 3, 4], SList!(2, 3)[]) == [2, 3, 4]);
Finds two or more needles into a haystack. The predicate pred is used throughout to compare elements. By default, elements are compared for equality.
Range haystack | The target of the search. Must be an input range. If any of needles is a range with elements comparable to elements in haystack, then haystack must be a forward range such that the search can backtrack. |
Ranges needles | One or more items to search for. Each of needles must be either comparable to one element in haystack, or be itself a forward range with elements comparable with elements in haystack. |
int[] a = [ 1, 4, 2, 3 ]; assert(find(a, 4) == [ 4, 2, 3 ]); assert(find(a, [ 1, 4 ]) == [ 1, 4, 2, 3 ]); assert(find(a, [ 1, 3 ], 4) == tuple([ 4, 2, 3 ], 2)); // Mixed types allowed if comparable assert(find(a, 5, [ 1.2, 3.5 ], 2.0, [ 1 ]) == tuple([ 2, 3 ], 3));
Advances the input range haystack by calling haystack.popFront until either pred(haystack.front), or haystack.empty. Performs Ο(haystack.length) evaluations of pred. See also STL's find_if.
To find the last element of a bidirectional haystack satisfying pred, call find!(pred)(retro(haystack)). See also std.range.retro.
auto arr = [ 1, 2, 3, 4, 1 ]; assert(find!("a > 2")(arr) == [ 3, 4, 1 ]); // with predicate alias bool pred(int x) { return x + 1 > 1.5; } assert(find!(pred)(arr) == arr);
If needle occurs in haystack, positions haystack right after the first occurrence of needle and returns true. Otherwise, leaves haystack as is and returns false.
string s = "abcdef"; assert(findSkip(s, "cd") && s == "ef"); s = "abcdef"; assert(!findSkip(s, "cxd") && s == "abcdef"); assert(findSkip(s, "def") && s.empty);
These functions find the first occurrence of needle in haystack and then split haystack as follows.
findSplit returns a tuple result containing three
ranges. result[0] is the portion of haystack before needle, result[1] is the portion of haystack that matches
needle, and result[2] is the portion of haystack after
the match. If needle was not found, result[0]
comprehends haystack entirely and result[1] and result[2]
are empty.
findSplitBefore returns a tuple result containing two
ranges. result[0] is the portion of haystack before needle, and result[1] is the balance of haystack starting
with the match. If needle was not found, result[0]
comprehends haystack entirely and result[1] is empty.
findSplitAfter returns a tuple result containing two ranges.
result[0] is the portion of haystack up to and including the
match, and result[1] is the balance of haystack starting
after the match. If needle was not found, result[0] is empty
and result[1] is haystack.
In all cases, the concatenation of the returned ranges spans the
entire haystack.
If haystack is a random-access range, all three components of the
tuple have the same type as haystack. Otherwise, haystack
must be a forward range and the type of result[0] and result[1] is the same as std.range.takeExactly.
auto a = "Carl Sagan Memorial Station"; auto r = findSplit(a, "Velikovsky"); assert(r[0] == a); assert(r[1].empty); assert(r[2].empty); r = findSplit(a, " "); assert(r[0] == "Carl"); assert(r[1] == " "); assert(r[2] == "Sagan Memorial Station"); auto r1 = findSplitBefore(a, "Sagan"); assert(r1[0] == "Carl ", r1[0]); assert(r1[1] == "Sagan Memorial Station"); auto r2 = findSplitAfter(a, "Sagan"); assert(r2[0] == "Carl Sagan"); assert(r2[1] == " Memorial Station");
Returns the number of elements which must be popped from the front of haystack before reaching an element for which startsWith!pred(haystack, needles) is true. If startsWith!pred(haystack, needles) is not true for any element in haystack, then -1 is returned.
needles may be either an element or a range.
assert(countUntil("hello world", "world") == 6); assert(countUntil("hello world", 'r') == 8); assert(countUntil("hello world", "programming") == -1); assert(countUntil("日本語", "本語") == 1); assert(countUntil("日本語", '語') == 2); assert(countUntil("日本語", "五") == -1); assert(countUntil("日本語", '五') == -1); assert(countUntil([0, 7, 12, 22, 9], [12, 22]) == 2); assert(countUntil([0, 7, 12, 22, 9], 9) == 4); assert(countUntil!"a > b"([0, 7, 12, 22, 9], 20) == 3);
Returns the number of elements which must be popped from haystack before pred(haystack.front) is true.
assert(countUntil!(std.uni.isWhite)("hello world") == 5); assert(countUntil!(std.ascii.isDigit)("hello world") == -1); assert(countUntil!"a > 20"([0, 7, 12, 22, 9]) == 3);
Interval option specifier for until (below) and others.
Lazily iterates range until value sentinel is found, at which point it stops.
int[] a = [ 1, 2, 4, 7, 7, 2, 4, 7, 3, 5]; assert(equal(a.until(7), [1, 2, 4][])); assert(equal(a.until(7, OpenRight.no), [1, 2, 4, 7][]));
If the range doesThisStart starts with any of the withOneOfThese ranges or elements, returns 1 if it starts with withOneOfThese[0], 2 if it starts with withOneOfThese[1], and so on. If none match, returns 0. In the case where doesThisStart starts with multiple of the ranges or elements in withOneOfThese, then the shortest one matches (if there are two which match which are of the same length (e.g. "a" and 'a'), then the left-most of them in the argument list matches).
assert(startsWith("abc", "")); assert(startsWith("abc", "a")); assert(!startsWith("abc", "b")); assert(startsWith("abc", 'a', "b") == 1); assert(startsWith("abc", "b", "a") == 2); assert(startsWith("abc", "a", "a") == 1); assert(startsWith("abc", "ab", "a") == 2); assert(startsWith("abc", "x", "a", "b") == 2); assert(startsWith("abc", "x", "aa", "ab") == 3); assert(startsWith("abc", "x", "aaa", "sab") == 0); assert(startsWith("abc", "x", "aaa", "a", "sab") == 3);
If startsWith(r1, r2), consume the corresponding elements off r1 and return true. Otherwise, leave r1 unchanged and return false.
Checks whether a range starts with an element, and if so, consume that element off r and return true. Otherwise, leave r unchanged and return false.
The reciprocal of startsWith.
assert(endsWith("abc", "")); assert(!endsWith("abc", "b")); assert(endsWith("abc", "a", 'c') == 2); assert(endsWith("abc", "c", "a") == 1); assert(endsWith("abc", "c", "c") == 1); assert(endsWith("abc", "bc", "c") == 2); assert(endsWith("abc", "x", "c", "b") == 2); assert(endsWith("abc", "x", "aa", "bc") == 3); assert(endsWith("abc", "x", "aaa", "sab") == 0); assert(endsWith("abc", "x", "aaa", 'c', "sab") == 3);
Returns the common prefix of two ranges. Example:
assert(commonPrefix("hello, world", "hello, there") == "hello, ");
Advances r until it finds the first two adjacent elements a, b that satisfy pred(a, b). Performs Ο(r.length) evaluations of pred. See also STL's adjacent_find.
int[] a = [ 11, 10, 10, 9, 8, 8, 7, 8, 9 ]; auto r = findAdjacent(a); assert(r == [ 10, 10, 9, 8, 8, 7, 8, 9 ]); p = findAdjacent!("a < b")(a); assert(p == [ 7, 8, 9 ]);
Advances seq by calling seq.popFront until either find!(pred)(choices, seq.front) is true, or seq becomes empty. Performs Ο(seq.length * choices.length) evaluations of pred. See also STL's find_first_of.
int[] a = [ -1, 0, 1, 2, 3, 4, 5 ]; int[] b = [ 3, 1, 2 ]; assert(findAmong(a, b) == a[2 .. $]);
The first version counts the number of elements x in r for which pred(x, value) is true. pred defaults to equality. Performs Ο(r.length) evaluations of pred.
The second version returns the number of times needle occurs in
haystack. Throws an exception if needle.empty, as the count
of the empty range in any range would be infinite. Overlapped counts
are not considered, for example count("aaa", "aa") is 1, not
2.
The third version counts the elements for which pred(x) is true. Performs Ο(r.length) evaluations of pred.
// count elements in range int[] a = [ 1, 2, 4, 3, 2, 5, 3, 2, 4 ]; assert(count(a, 2) == 3); assert(count!("a > b")(a, 2) == 5); // count range in range assert(count("abcadfabf", "ab") == 2); assert(count("ababab", "abab") == 1); assert(count("ababab", "abx") == 0); // fuzzy count range in range assert(count!"std.uni.toLower(a) == std.uni.toLower(b)"("AbcAdFaBf", "ab") == 2); // count predicate in range assert(count!("a > 1")(a) == 8);
Checks whether r has "balanced parentheses", i.e. all instances of lPar are closed by corresponding instances of rPar. The parameter maxNestingLevel controls the nesting level allowed. The most common uses are the default or 0. In the latter case, no nesting is allowed.
auto s = "1 + $(LPAREN)2 * (3 + 1 / 2)"; assert(!balancedParens(s, '(', ')')); s = "1 + (2 * (3 + 1) / 2)"; assert(balancedParens(s, '(', ')')); s = "1 + (2 * (3 + 1) / 2)"; assert(!balancedParens(s, '(', ')', 1)); s = "1 + (2 * 3 + 1) / (2 - 5)"; assert(balancedParens(s, '(', ')', 1));
Returns true if and only if the two ranges compare equal element for element, according to binary predicate pred. The ranges may have different element types, as long as pred(a, b) evaluates to bool for a in r1 and b in r2. Performs Ο(min(r1.length, r2.length)) evaluations of pred. See also STL's equal.
int[] a = [ 1, 2, 4, 3 ]; assert(!equal(a, a[1..$])); assert(equal(a, a)); // different types double[] b = [ 1.0, 2, 4, 3]; assert(!equal(a, b[1..$])); assert(equal(a, b)); // predicated: ensure that two vectors are approximately equal double[] c = [ 1.005, 2, 4, 3]; assert(equal!(approxEqual)(b, c));
Performs three-way lexicographical comparison on two input ranges according to predicate pred. Iterating r1 and r2 in lockstep, cmp compares each element e1 of r1 with the corresponding element e2 in r2. If binaryFun!pred(e1, e2), cmp returns a negative value. If binaryFun!pred(e2, e1), cmp returns a positive value. If one of the ranges has been finished, cmp returns a negative value if r1 has fewer elements than r2, a positive value if r1 has more elements than r2, and 0 if the ranges have the same number of elements.
If the ranges are strings, cmp performs UTF decoding appropriately and compares the ranges one code point at a time.
Returns the minimum of the passed-in values. The type of the result is computed by using std.traits.CommonType.
Returns the maximum of the passed-in values. The type of the result is computed by using std.traits.CommonType.
int a = 5; short b = 6; double c = 2; auto d = max(a, b); assert(is(typeof(d) == int)); assert(d == 6); auto e = min(a, b, c); assert(is(typeof(e) == double)); assert(e == 2);
Returns the minimum element of a range together with the number of occurrences. The function can actually be used for counting the maximum or any other ordering predicate (that's why maxCount is not provided).
int[] a = [ 2, 3, 4, 1, 2, 4, 1, 1, 2 ]; // Minimum is 1 and occurs 3 times assert(minCount(a) == tuple(1, 3)); // Maximum is 4 and occurs 2 times assert(minCount!("a > b")(a) == tuple(4, 2));
Returns the position of the minimum element of forward range range, i.e. a subrange of range starting at the position of its smallest element and with the same ending as range. The function can actually be used for counting the maximum or any other ordering predicate (that's why maxPos is not provided).
int[] a = [ 2, 3, 4, 1, 2, 4, 1, 1, 2 ]; // Minimum is 1 and first occurs in position 3 assert(minPos(a) == [ 1, 2, 4, 1, 1, 2 ]); // Maximum is 4 and first occurs in position 2 assert(minPos!("a > b")(a) == [ 4, 1, 2, 4, 1, 1, 2 ]);
Sequentially compares elements in r1 and r2 in lockstep, and stops at the first mismatch (according to pred, by default equality). Returns a tuple with the reduced ranges that start with the two mismatched values. Performs Ο(min(r1.length, r2.length)) evaluations of pred. See also STL's mismatch.
int[] x = [ 1, 5, 2, 7, 4, 3 ]; double[] y = [ 1.0, 5, 2, 7.3, 4, 8 ]; auto m = mismatch(x, y); assert(m[0] == x[3 .. $]); assert(m[1] == y[3 .. $]);
Encodes edit operations necessary to transform one sequence into another. Given sequences s (source) and t (target), a sequence of EditOp encodes the steps that need to be taken to convert s into t. For example, if s = "cat" and "cars", the minimal sequence that transforms s into t is: skip two characters, replace 't' with 'r', and insert an 's'. Working with edit operations is useful in applications such as spell-checkers (to find the closest word to a given misspelled word), approximate searches, diff-style programs that compute the difference between files, efficient encoding of patches, DNA sequence analysis, and plagiarism detection.
Current items are equal; no editing is necessary.
Substitute current item in target with current item in source.
Insert current item from the source into the target.
Remove current item from the target.
Returns the Levenshtein distance between s and t. The Levenshtein distance computes the minimal amount of edit operations necessary to transform s into t. Performs Ο(s.length * t.length) evaluations of equals and occupies Ο(s.length * t.length) storage.
assert(levenshteinDistance("cat", "rat") == 1); assert(levenshteinDistance("parks", "spark") == 2); assert(levenshteinDistance("kitten", "sitting") == 3); // ignore case assert(levenshteinDistance!("std.uni.toUpper(a) == std.uni.toUpper(b)") ("parks", "SPARK") == 2);
Returns the Levenshtein distance and the edit path between s and t.
string a = "Saturday", b = "Sunday"; auto p = levenshteinDistanceAndPath(a, b); assert(p[0] == 3); assert(equal(p[1], "nrrnsnnn"));
Copies the content of source into target and returns the remaining (unfilled) part of target. See also STL's copy. If a behavior similar to STL's copy_backward is needed, use copy(retro(source), retro(target)). See also std.range.retro.
int[] a = [ 1, 5 ]; int[] b = [ 9, 8 ]; int[] c = new int[a.length + b.length + 10]; auto d = copy(b, copy(a, c)); assert(c[0 .. a.length + b.length] == a ~ b); assert(d.length == 10);
float[] a = [ 1.0f, 5 ]; double[] b = new double[a.length]; auto d = copy(a, b);
int[] a = [ 1, 5, 8, 9, 10, 1, 2, 0 ]; auto b = new int[a.length]; auto c = copy(filter!("(a & 1) == 1")(a), b); assert(b[0 .. $ - c.length] == [ 1, 5, 9, 1 ]);
Swaps all elements of r1 with successive elements in r2. Returns a tuple containing the remainder portions of r1 and r2 that were not swapped (one of them will be empty). The ranges may be of different types but must have the same element type and support swapping.
int[] a = [ 100, 101, 102, 103 ]; int[] b = [ 0, 1, 2, 3 ]; auto c = swapRanges(a[1 .. 3], b[2 .. 4]); assert(c[0].empty && c[1].empty); assert(a == [ 100, 2, 3, 103 ]); assert(b == [ 0, 1, 101, 102 ]);
Reverses r in-place. Performs r.length / 2 evaluations of swap. See also STL's reverse.
int[] arr = [ 1, 2, 3 ]; reverse(arr); assert(arr == [ 3, 2, 1 ]);
Reverses r in-place, where r is a narrow string (having elements of type char or wchar). UTF sequences consisting of multiple code units are preserved properly.
char[] arr = "hello\U00010143\u0100\U00010143".dup; reverse(arr); assert(arr == "\U00010143\u0100\U00010143olleh");
The strip group of functions allow stripping of either leading, trailing, or both leading and trailing elements.
The stripLeft function will strip the front of the range,
the stripRight function will strip the back of the range,
while the strip function will strip both the front and back
of the range.
Note that the strip and stripRight functions require the range to
be a BidirectionalRange
range.
All of these functions come in two varieties: one takes a target element,
where the range will be stripped as long as this element can be found.
The other takes a lambda predicate, where the range will be stripped as
long as the predicate returns true.
assert(" foobar ".strip(' ') == "foobar"); assert("00223.444500".strip('0') == "223.4445"); assert("ëëêéüŗōpéêëë".strip('ë') == "êéüŗōpéê"); assert([1, 1, 0, 1, 1].strip(1) == [0]); assert([0.0, 0.01, 0.01, 0.0].strip(0).length == 2);
assert(" foobar ".strip!(a => a == ' ')() == "foobar"); assert("00223.444500".strip!(a => a == '0')() == "223.4445"); assert("ëëêéüŗōpéêëë".strip!(a => a == 'ë')() == "êéüŗōpéê"); assert([1, 1, 0, 1, 1].strip!(a => a == 1)() == [0]); assert([0.0, 0.01, 0.5, 0.6, 0.01, 0.0].strip!(a => a < 0.4)().length == 2);
assert(" foobar ".stripLeft(' ') == "foobar "); assert("00223.444500".stripLeft('0') == "223.444500"); assert("ůůűniçodêéé".stripLeft('ů') == "űniçodêéé"); assert([1, 1, 0, 1, 1].stripLeft(1) == [0, 1, 1]); assert([0.0, 0.01, 0.01, 0.0].stripLeft(0).length == 3);
assert(" foobar ".stripLeft!(a => a == ' ')() == "foobar "); assert("00223.444500".stripLeft!(a => a == '0')() == "223.444500"); assert("ůůűniçodêéé".stripLeft!(a => a == 'ů')() == "űniçodêéé"); assert([1, 1, 0, 1, 1].stripLeft!(a => a == 1)() == [0, 1, 1]); assert([0.0, 0.01, 0.10, 0.5, 0.6].stripLeft!(a => a < 0.4)().length == 2);
assert(" foobar ".stripRight(' ') == " foobar"); assert("00223.444500".stripRight('0') == "00223.4445"); assert("ùniçodêéé".stripRight('é') == "ùniçodê"); assert([1, 1, 0, 1, 1].stripRight(1) == [1, 1, 0]); assert([0.0, 0.01, 0.01, 0.0].stripRight(0).length == 3);
assert(" foobar ".stripRight!(a => a == ' ')() == " foobar"); assert("00223.444500".stripRight!(a => a == '0')() == "00223.4445"); assert("ùniçodêéé".stripRight!(a => a == 'é')() == "ùniçodê"); assert([1, 1, 0, 1, 1].stripRight!(a => a == 1)() == [1, 1, 0]); assert([0.0, 0.01, 0.10, 0.5, 0.6].stripRight!(a => a > 0.4)().length == 3);
The bringToFront function has considerable flexibility and usefulness. It can rotate elements in one buffer left or right, swap buffers of equal length, and even move elements across disjoint buffers of different types and different lengths.
bringToFront takes two ranges front and back, which may
be of different types. Considering the concatenation of front and
back one unified range, bringToFront rotates that unified
range such that all elements in back are brought to the beginning
of the unified range. The relative ordering of elements in front
and back, respectively, remains unchanged.
The simplest use of bringToFront is for rotating elements in a
buffer. For example:
auto arr = [4, 5, 6, 7, 1, 2, 3]; bringToFront(arr[0 .. 4], arr[4 .. $]); assert(arr == [ 1, 2, 3, 4, 5, 6, 7 ]);
auto list = SList!(int)(4, 5, 6, 7, 1, 2, 3); auto r1 = list[]; auto r2 = list[]; popFrontN(r2, 4); assert(equal(r2, [ 1, 2, 3 ])); bringToFront(r1, r2); assert(equal(list[], [ 1, 2, 3, 4, 5, 6, 7 ]));
auto list = SList!(int)(4, 5, 6, 7); auto vec = [ 1, 2, 3 ]; bringToFront(list[], vec); assert(equal(list[], [ 1, 2, 3, 4 ])); assert(equal(vec, [ 5, 6, 7 ]));
Defines the swapping strategy for algorithms that need to swap elements in a range (such as partition and sort). The strategy concerns the swapping of elements that are not the core concern of the algorithm. For example, consider an algorithm that sorts [ "abc", "b", "aBc" ] according to toUpper(a) < toUpper(b). That algorithm might choose to swap the two equivalent strings "abc" and "aBc". That does not affect the sorting since both [ "abc", "aBc", "b" ] and [ "aBc", "abc", "b" ] are valid outcomes.
Some situations require that the algorithm must NOT ever change the
relative ordering of equivalent elements (in the example above, only
[ "abc", "aBc", "b" ] would be the correct result). Such
algorithms are called stable. If the ordering algorithm may swap
equivalent elements discretionarily, the ordering is called unstable.
Yet another class of algorithms may choose an intermediate tradeoff by
being stable only on a well-defined subrange of the range. There is no
established terminology for such behavior; this library calls it semistable.
Generally, the stable ordering strategy may be more costly in
time and/or space than the other two because it imposes additional
constraints. Similarly, semistable may be costlier than unstable. As (semi-)stability is not needed very often, the ordering
algorithms in this module parameterized by SwapStrategy all
choose SwapStrategy.unstable as the default.
Allows freely swapping of elements as long as the output satisfies the algorithm's requirements.
In algorithms partitioning ranges in two, preserve relative ordering of elements only to the left of the partition point.
Preserve the relative ordering of elements to the largest extent allowed by the algorithm's requirements.
Eliminates elements at given offsets from range and returns the shortened range. In the simplest call, one element is removed.
int[] a = [ 3, 5, 7, 8 ]; assert(remove(a, 1) == [ 3, 7, 8 ]); assert(a == [ 3, 7, 8, 8 ]);
int[] a = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]; assert(remove(a, 1, 3, 5) == [ 0, 2, 4, 6, 7, 8, 9, 10 ]);
int[] a = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]; assert(remove(a, 1, tuple(3, 5), 9) == [ 0, 2, 6, 7, 8, 10 ]);
int[] a = [ 0, 1, 2, 3 ]; assert(remove!(SwapStrategy.unstable)(a, 1) == [ 0, 3, 2 ]);
Reduces the length of the bidirectional range range by removing elements that satisfy pred. If s = SwapStrategy.unstable, elements are moved from the right end of the range over the elements to eliminate. If s = SwapStrategy.stable (the default), elements are moved progressively to front such that their relative order is preserved. Returns the filtered range.
int[] a = [ 1, 2, 3, 2, 3, 4, 5, 2, 5, 6 ]; assert(remove!("a == 2")(a) == [ 1, 3, 3, 4, 5, 5, 6 ]);
Partitions a range in two using pred as a predicate. Specifically, reorders the range r = [left, right) using swap such that all elements i for which pred(i) is true come before all elements j for which pred(j) returns false.
Performs Ο(r.length) (if unstable or semistable) or Ο(r.length * log(r.length)) (if stable) evaluations of less and swap. The unstable version computes the minimum possible evaluations
of swap (roughly half of those performed by the semistable
version).
See also STL's partition and
stable_partition.
auto Arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]; auto arr = Arr.dup; static bool even(int a) { return (a & 1) == 0; } // Partition arr such that even numbers come first auto r = partition!(even)(arr); // Now arr is separated in evens and odds. // Numbers may have become shuffled due to instability assert(r == arr[5 .. $]); assert(count!(even)(arr[0 .. 5]) == 5); assert(find!(even)(r).empty); // Can also specify the predicate as a string. // Use 'a' as the predicate argument name arr[] = Arr[]; r = partition!(q{(a & 1) == 0})(arr); assert(r == arr[5 .. $]); // Now for a stable partition: arr[] = Arr[]; r = partition!(q{(a & 1) == 0}, SwapStrategy.stable)(arr); // Now arr is [2 4 6 8 10 1 3 5 7 9], and r points to 1 assert(arr == [2, 4, 6, 8, 10, 1, 3, 5, 7, 9] && r == arr[5 .. $]); // In case the predicate needs to hold its own state, use a delegate: arr[] = Arr[]; int x = 3; // Put stuff greater than 3 on the left bool fun(int a) { return a > x; } r = partition!(fun, SwapStrategy.semistable)(arr); // Now arr is [4 5 6 7 8 9 10 2 3 1] and r points to 2 assert(arr == [4, 5, 6, 7, 8, 9, 10, 2, 3, 1] && r == arr[7 .. $]);
Returns true if r is partitioned according to predicate pred.
int[] r = [ 1, 3, 5, 7, 8, 2, 4, ]; assert(isPartitioned!("a & 1")(r));
Rearranges elements in r in three adjacent ranges and returns them. The first and leftmost range only contains elements in r less than pivot. The second and middle range only contains elements in r that are equal to pivot. Finally, the third and rightmost range only contains elements in r that are greater than pivot. The less-than test is defined by the binary function less.
auto a = [ 8, 3, 4, 1, 4, 7, 4 ]; auto pieces = partition3(a, 4); assert(a == [ 1, 3, 4, 4, 4, 7, 8 ]); assert(pieces[0] == [ 1, 3 ]); assert(pieces[1] == [ 4, 4, 4 ]); assert(pieces[2] == [ 7, 8 ]);
Reorders the range r using swap such that r[nth] refers to the element that would fall there if the range were fully sorted. In addition, it also partitions r such that all elements e1 from r[0] to r[nth] satisfy !less(r[nth], e1), and all elements e2 from r[nth] to r[r.length] satisfy !less(e2, r[nth]). Effectively, it finds the nth smallest (according to less) elements in r. Performs an expected Ο(r.length) (if unstable) or Ο(r.length * log(r.length)) (if stable) evaluations of less and swap. See also STL's nth_element.
If n >= r.length, the algorithm has no effect.
int[] v = [ 25, 7, 9, 2, 0, 5, 21 ]; auto n = 4; topN!(less)(v, n); assert(v[n] == 9); // Equivalent form: topN!("a < b")(v, n); assert(v[n] == 9);
Stores the smallest elements of the two ranges in the left-hand range.
int[] a = [ 5, 7, 2, 6, 7 ]; int[] b = [ 2, 1, 5, 6, 7, 3, 0 ]; topN(a, b); sort(a); assert(a == [0, 1, 2, 2, 3]);
Sorts a random-access range according to the predicate less. Performs Ο(r.length * log(r.length)) (if unstable) or Ο(r.length * log(r.length) * log(r.length)) (if stable) evaluations of less and swap. See also STL's sort and stable_sort.
sort returns a std.range.SortedRange over the original range, which functions that can take advantage of sorted data can then use to know that the range is sorted and adjust accordingly. The std.range.SortedRange is a wrapper around the original range, so both it and the original range are sorted, but other functions won't know that the original range has been sorted, whereas they can know that std.range.SortedRange has been sorted.
int[] array = [ 1, 2, 3, 4 ]; // sort in descending order sort!("a > b")(array); assert(array == [ 4, 3, 2, 1 ]); // sort in ascending order sort(array); assert(array == [ 1, 2, 3, 4 ]); // sort with a delegate bool myComp(int x, int y) { return x > y; } sort!(myComp)(array); assert(array == [ 4, 3, 2, 1 ]); // Showcase stable sorting string[] words = [ "aBc", "a", "abc", "b", "ABC", "c" ]; sort!("toUpper(a) < toUpper(b)", SwapStrategy.stable)(words); assert(words == [ "a", "aBc", "abc", "ABC", "b", "c" ]);
void multiSort(Range)(Range r) if (validPredicates!(ElementType!Range, less));
Sorts a range by multiple keys. The call multiSort!("a.id < b.id", "a.date > b.date")(r) sorts the range r by id ascending, and sorts elements that have the same id by date descending. Such a call is equivalent to sort!"a.id != b.id ? a.id < b.id : a.date > b.date"(r), but multiSort is faster because it does fewer comparisons (in addition to being more convenient).
static struct Point { int x, y; } auto pts1 = [ Point(0, 0), Point(5, 5), Point(0, 1), Point(0, 2) ]; auto pts2 = [ Point(0, 0), Point(0, 1), Point(0, 2), Point(5, 5) ]; multiSort!("a.x < b.x", "a.y < b.y", SwapStrategy.unstable)(pts1); assert(pts1 == pts2);
Sorts a range using an algorithm akin to the Schwartzian transform, also known as the decorate-sort-undecorate pattern in Python and Lisp. (Not to be confused with the other Schwartz.) This function is helpful when the sort comparison includes an expensive computation. The complexity is the same as that of the corresponding sort, but schwartzSort evaluates transform only r.length times (less than half when compared to regular sorting). The usage can be best illustrated with an example.
uint hashFun(string) { ... expensive computation ... } string[] array = ...; // Sort strings by hash, slow sort!((a, b) => hashFun(a) < hashFun(b))(array); // Sort strings by hash, fast (only computes arr.length hashes): schwartzSort!(hashFun, "a < b")(array);
Reorders the random-access range r such that the range r[0 .. mid] is the same as if the entire r were sorted, and leaves the range r[mid .. r.length] in no particular order. Performs Ο(r.length * log(mid)) evaluations of pred. The implementation simply calls topN!(less, ss)(r, n) and then sort!(less, ss)(r[0 .. n]).
int[] a = [ 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 ]; partialSort(a, 5); assert(a[0 .. 5] == [ 0, 1, 2, 3, 4 ]);
Sorts the random-access range chain(lhs, rhs) according to predicate less. The left-hand side of the range lhs is assumed to be already sorted; rhs is assumed to be unsorted. The exact strategy chosen depends on the relative sizes of lhs and rhs. Performs Ο(lhs.length + rhs.length * log(rhs.length)) (best case) to Ο((lhs.length + rhs.length) * log(lhs.length + rhs.length)) (worst-case) evaluations of swap.
int[] a = [ 1, 2, 3 ]; int[] b = [ 4, 0, 6, 5 ]; completeSort(assumeSorted(a), b); assert(a == [ 0, 1, 2 ]); assert(b == [ 3, 4, 5, 6 ]);
Checks whether a forward range is sorted according to the comparison operation less. Performs Ο(r.length) evaluations of less.
int[] arr = [4, 3, 2, 1]; assert(!isSorted(arr)); sort(arr); assert(isSorted(arr)); sort!("a > b")(arr); assert(isSorted!("a > b")(arr));
Computes an index for r based on the comparison less. The index is a sorted array of pointers or indices into the original range. This technique is similar to sorting, but it is more flexible because (1) it allows "sorting" of immutable collections, (2) allows binary search even if the original collection does not offer random access, (3) allows multiple indexes, each on a different predicate, and (4) may be faster when dealing with large objects. However, using an index may also be slower under certain circumstances due to the extra indirection, and is always larger than a sorting-based solution because it needs space for the index in addition to the original collection. The complexity is the same as sort's.
The first overload of makeIndex writes to a range containing
pointers, and the second writes to a range containing offsets. The
first overload requires Range to be a forward range, and the
latter requires it to be a random-access range.
makeIndex overwrites its second argument with the result, but
never reallocates it.
immutable(int[]) arr = [ 2, 3, 1, 5, 0 ]; // index using pointers auto index1 = new immutable(int)*[arr.length]; makeIndex!("a < b")(arr, index1); assert(isSorted!("*a < *b")(index1)); // index using offsets auto index2 = new size_t[arr.length]; makeIndex!("a < b")(arr, index2); assert(isSorted! ((size_t a, size_t b){ return arr[a] < arr[b];}) (index2));
Specifies whether the output of certain algorithm is desired in sorted format.
Returns true if and only if value can be found in range. Performs Ο(needle.length) evaluations of pred.
Returns the 1-based index of the first needle found in haystack. If no needle is found, then 0 is returned.
So, if used directly in the condition of an if statement or loop, the result will be true if one of the needles is found and false if none are found, whereas if the result is used elsewhere, it can either be cast to bool for the same effect or used to get which needle was found first without having to deal with the tuple that LREF find returns for the same operation.
Returns true if and only if a value v satisfying the predicate pred can be found in the forward range range. Performs Ο(r.length) evaluations of pred.
Returns true if and only if all values in range satisfy the predicate pred. Performs Ο(r.length) evaluations of pred.
assert(all!"a & 1"([1, 3, 5, 7, 9])); assert(!all!"a & 1"([1, 2, 3, 5, 7, 9]));
Copies the top n elements of the input range source into the random-access range target, where n = target.length. Elements of source are not touched. If sorted is true, the target is sorted. Otherwise, the target respects the heap property.
int[] a = [ 10, 16, 2, 3, 1, 5, 0 ]; int[] b = new int[3]; topNCopy(a, b, true); assert(b == [ 0, 1, 2 ]);
Lazily computes the union of two or more ranges rs. The ranges are assumed to be sorted by less. Elements in the output are not unique; the length of the output is the sum of the lengths of the inputs. (The length member is offered if all ranges also have length.) The element types of all ranges must have a common type.
int[] a = [ 1, 2, 4, 5, 7, 9 ]; int[] b = [ 0, 1, 2, 4, 7, 8 ]; int[] c = [ 10 ]; assert(setUnion(a, b).length == a.length + b.length); assert(equal(setUnion(a, b), [0, 1, 1, 2, 2, 4, 4, 5, 7, 7, 8, 9][])); assert(equal(setUnion(a, c, b), [0, 1, 1, 2, 2, 4, 4, 5, 7, 7, 8, 9, 10][]));
Lazily computes the intersection of two or more input ranges rs. The ranges are assumed to be sorted by less. The element types of all ranges must have a common type.
int[] a = [ 1, 2, 4, 5, 7, 9 ]; int[] b = [ 0, 1, 2, 4, 7, 8 ]; int[] c = [ 0, 1, 4, 5, 7, 8 ]; assert(equal(setIntersection(a, a), a)); assert(equal(setIntersection(a, b), [1, 2, 4, 7][])); assert(equal(setIntersection(a, b, c), [1, 4, 7][]));
Lazily computes the difference of r1 and r2. The two ranges are assumed to be sorted by less. The element types of the two ranges must have a common type.
int[] a = [ 1, 2, 4, 5, 7, 9 ]; int[] b = [ 0, 1, 2, 4, 7, 8 ]; assert(equal(setDifference(a, b), [5, 9][]));
Lazily computes the symmetric difference of r1 and r2, i.e. the elements that are present in exactly one of r1 and r2. The two ranges are assumed to be sorted by less, and the output is also sorted by less. The element types of the two ranges must have a common type.
int[] a = [ 1, 2, 4, 5, 7, 9 ]; int[] b = [ 0, 1, 2, 4, 7, 8 ]; assert(equal(setSymmetricDifference(a, b), [0, 5, 8, 9][]));
Computes the union of multiple sets. The input sets are passed as a range of ranges and each is assumed to be sorted by less. Computation is done lazily, one union element at a time. The complexity of one popFront operation is Ο(log(ror.length)). However, the length of ror decreases as ranges in it are exhausted, so the complexity of a full pass through NWayUnion is dependent on the distribution of the lengths of ranges contained within ror. If all ranges have the same length n (worst case scenario), the complexity of a full pass through NWayUnion is Ο(n * ror.length * log(ror.length)), i.e., log(ror.length) times worse than just spanning all ranges in turn. The output comes sorted (unstably) by less.
double[][] a = [ [ 1, 4, 7, 8 ], [ 1, 7 ], [ 1, 7, 8], [ 4 ], [ 7 ], ]; auto witness = [ 1, 1, 1, 4, 4, 7, 7, 7, 7, 8, 8 ]; assert(equal(nWayUnion(a), witness[]));
Given a range of sorted forward ranges ror, copies to tgt the elements that are common to most ranges, along with their number of occurrences. All ranges in ror are assumed to be sorted by less. Only the most frequent tgt.length elements are returned.
// Figure which number can be found in most arrays of the set of // arrays below. double[][] a = [ [ 1, 4, 7, 8 ], [ 1, 7 ], [ 1, 7, 8], [ 4 ], [ 7 ], ]; auto b = new Tuple!(double, uint)[1]; largestPartialIntersection(a, b); // First member is the item, second is the occurrence count assert(b[0] == tuple(7.0, 4u));
Similar to largestPartialIntersection, but associates a weight with each distinct element in the intersection.
// Figure which number can be found in most arrays of the set of // arrays below, with specific per-element weights double[][] a = [ [ 1, 4, 7, 8 ], [ 1, 7 ], [ 1, 7, 8], [ 4 ], [ 7 ], ]; auto b = new Tuple!(double, uint)[1]; double[double] weights = [ 1:1.2, 4:2.3, 7:1.1, 8:1.1 ]; largestPartialIntersectionWeighted(a, b, weights); // First member is the item, second is the occurrence count assert(b[0] == tuple(4.0, 2u));
Permutes range in-place to the next lexicographically greater permutation.
The predicate less defines the lexicographical ordering to be used on
the range.
If the range is currently the lexicographically greatest permutation, it is
permuted back to the least permutation and false is returned. Otherwise,
true is returned. One can thus generate all permutations of a range by
sorting it according to less, which produces the lexicographically
least permutation, and then calling nextPermutation until it returns false.
This is guaranteed to generate all distinct permutations of the range
exactly once. If there are N elements in the range and all of them are
unique, then N! permutations will be generated. Otherwise, if there are
some duplicated elements, fewer permutations will be produced.
// Enumerate all permutations int[] a = [1,2,3,4,5]; while (nextPermutation(a)) { // a now contains the next permutation of the array. }
// Step through all permutations of a sorted array in lexicographic order int[] a = [1,2,3]; assert(nextPermutation(a) == true); assert(a == [1,3,2]); assert(nextPermutation(a) == true); assert(a == [2,1,3]); assert(nextPermutation(a) == true); assert(a == [2,3,1]); assert(nextPermutation(a) == true); assert(a == [3,1,2]); assert(nextPermutation(a) == true); assert(a == [3,2,1]); assert(nextPermutation(a) == false); assert(a == [1,2,3]);
// Step through permutations of an array containing duplicate elements: int[] a = [1,1,2]; assert(nextPermutation(a) == true); assert(a == [1,2,1]); assert(nextPermutation(a) == true); assert(a == [2,1,1]); assert(nextPermutation(a) == false); assert(a == [1,1,2]);
Permutes range in-place to the next lexicographically greater even permutation.
The predicate less defines the lexicographical ordering to be used on
the range.
An even permutation is one which is produced by swapping an even number of
pairs of elements in the original range. The set of even permutations
is distinct from the set of all permutations only when there are no
duplicate elements in the range. If the range has N unique elements,
then there are exactly N!/2 even permutations.
If the range is already the lexicographically greatest even permutation, it
is permuted back to the least even permutation and false is returned.
Otherwise, true is returned, and the range is modified in-place to be the
lexicographically next even permutation.
One can thus generate the even permutations of a range with unique elements
by starting with the lexicographically smallest permutation, and repeatedly
calling nextEvenPermutation until it returns false.
// Enumerate even permutations int[] a = [1,2,3,4,5]; while (nextEvenPermutation(a)) { // a now contains the next even permutation of the array. }One can also generate the odd permutations of a range by noting that permutations obey the rule that even + even = even, and odd + even = odd. Thus, by swapping the last two elements of a lexicographically least range, it is turned into the first odd permutation. Then calling nextEvenPermutation on this first odd permutation will generate the next even permutation relative to this odd permutation, which is actually the next odd permutation of the original range. Thus, by repeatedly calling nextEvenPermutation until it returns false, one enumerates the odd permutations of the original range.
// Enumerate odd permutations int[] a = [1,2,3,4,5]; swap(a[$-2], a[$-1]); // a is now the first odd permutation of [1,2,3,4,5] while (nextEvenPermutation(a)) { // a now contains the next odd permutation of the original array // (which is an even permutation of the first odd permutation). }
// Step through even permutations of a sorted array in lexicographic order int[] a = [1,2,3]; assert(nextEvenPermutation(a) == true); assert(a == [2,3,1]); assert(nextEvenPermutation(a) == true); assert(a == [3,1,2]); assert(nextEvenPermutation(a) == false); assert(a == [1,2,3]);Even permutations are useful for generating coordinates of certain geometric shapes. Here's a non-trivial example:
// Print the 60 vertices of a uniform truncated icosahedron (soccer ball) import std.math, std.stdio; enum real Phi = (1.0 + sqrt(5.0)) / 2.0; // Golden ratio real[][] seeds = [ [0.0, 1.0, 3.0*Phi], [1.0, 2.0+Phi, 2.0*Phi], [Phi, 2.0, Phi^^3] ]; foreach (seed; seeds) { // Loop over even permutations of each seed do { // Loop over all sign changes of each permutation size_t i; do { // Generate all possible sign changes for (i=0; i < seed.length; i++) { if (seed[i] != 0.0) { seed[i] = -seed[i]; if (seed[i] < 0.0) break; } } writeln(seed); } while (i < seed.length); } while (nextEvenPermutation(seed)); }
Lazily computes the Cartesian product of two or more ranges. The product is a range of tuples of elements from each respective range.
The conditions for the two-range case are as follows:
If both ranges are finite, then one must be (at least) a forward range and the
other an input range.
If one range is infinite and the other finite, then the finite range must
be a forward range, and the infinite range can be an input range.
If both ranges are infinite, then both must be forward ranges.
When there are more than two ranges, the above conditions apply to each
adjacent pair of ranges.
auto N = sequence!"n"(0); // the range of natural numbers auto N2 = cartesianProduct(N, N); // the range of all pairs of natural numbers // Various arbitrary number pairs can be found in the range in finite time. assert(canFind(N2, tuple(0, 0))); assert(canFind(N2, tuple(123, 321))); assert(canFind(N2, tuple(11, 35))); assert(canFind(N2, tuple(279, 172)));
auto B = [ 1, 2, 3 ]; auto C = [ 4, 5, 6 ]; auto BC = cartesianProduct(B, C); foreach (n; [[1, 4], [2, 4], [3, 4], [1, 5], [2, 5], [3, 5], [1, 6], [2, 6], [3, 6]]) { assert(canFind(BC, tuple(n[0], n[1]))); }
auto A = [ 1, 2, 3 ]; auto B = [ 'a', 'b', 'c' ]; auto C = [ "x", "y", "z" ]; auto ABC = cartesianProduct(A, B, C); assert(ABC.equal([ tuple(1, 'a', "x"), tuple(2, 'a', "x"), tuple(3, 'a', "x"), tuple(1, 'b', "x"), tuple(2, 'b', "x"), tuple(3, 'b', "x"), tuple(1, 'c', "x"), tuple(2, 'c', "x"), tuple(3, 'c', "x"), tuple(1, 'a', "y"), tuple(2, 'a', "y"), tuple(3, 'a', "y"), tuple(1, 'b', "y"), tuple(2, 'b', "y"), tuple(3, 'b', "y"), tuple(1, 'c', "y"), tuple(2, 'c', "y"), tuple(3, 'c', "y"), tuple(1, 'a', "z"), tuple(2, 'a', "z"), tuple(3, 'a', "z"), tuple(1, 'b', "z"), tuple(2, 'b', "z"), tuple(3, 'b', "z"), tuple(1, 'c', "z"), tuple(2, 'c', "z"), tuple(3, 'c', "z") ]));