This is a submodule of std.algorithm. It contains generic searching algorithms.
| Function Name | Description |
|---|---|
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. |
commonPrefix | commonPrefix("parakeet", "parachute") returns "para". |
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 "de" 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). |
maxCount | maxCount([2, 4, 1, 4, 1]) returns tuple(4, 2). |
minElement | Selects the minimal element of a range. minElement([3, 4, 1, 2]) returns 1. |
maxElement | Selects the maximal element of a range. maxElement([3, 4, 1, 2]) returns 4. |
minIndex | Index of the minimal element of a range. minElement([3, 4, 1, 2]) returns 2. |
maxIndex | Index of the maximal element of a range. maxElement([3, 4, 1, 2]) returns 1. |
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. |
maxPos | maxPos([2, 3, 1, 3, 4, 1]) returns the subrange [4, 1], i.e., positions the range at the first occurrence of its maximal 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. |
Checks if all of the elements verify pred.
assert( all!"a & 1"([1, 3, 5, 7, 9])); assert(!all!"a & 1"([1, 2, 3, 5, 7, 9]));
all can also be used without a predicate, if its items can be evaluated to true or false in a conditional statement. This can be a convenient way to quickly evaluate that all of the elements of a range are true. int[3] vals = [5, 3, 18]; assert( all(vals[]));
Returns true if and only if all values v found in the input range range satisfy the predicate pred. Performs (at most) Ο(range.length) evaluations of pred.
Checks if any of the elements verifies pred. !any can be used to verify that none of the elements verify pred. This is sometimes called exists in other languages.
import std.ascii : isWhite; assert( all!(any!isWhite)(["a a", "b b"])); assert(!any!(all!isWhite)(["a a", "b b"]));
any can also be used without a predicate, if its items can be evaluated to true or false in a conditional statement. !any can be a convenient way to quickly test that none of the elements of a range evaluate to true. int[3] vals1 = [0, 0, 0]; assert(!any(vals1[])); //none of vals1 evaluate to true int[3] vals2 = [2, 0, 2]; assert( any(vals2[])); assert(!all(vals2[])); int[3] vals3 = [3, 3, 3]; assert( any(vals3[])); assert( all(vals3[]));
Returns true if and only if any value v found in the input range range satisfies the predicate pred. Performs (at most) Ο(range.length) evaluations of pred.
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.
Range r
| The range to check. |
E lPar
| The element corresponding with a left (opening) parenthesis. |
E rPar
| The element corresponding with a right (closing) parenthesis. |
size_t maxNestingLevel
| The maximum allowed nesting level. |
auto s = "1 + (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, '(', ')', 0));
s = "1 + (2 * 3 + 1) / (2 - 5)";
assert(balancedParens(s, '(', ')', 0));
s = "f(x) = ⌈x⌉";
assert(balancedParens(s, '⌈', '⌉'));
Sets up Boyer-Moore matching for use with find below. By default, elements are compared for equality.
BoyerMooreFinder allocates GC memory.
| pred | Predicate used to compare elements. |
Range needle
| A random-access range with length and slicing. |
BoyerMooreFinder that can be used with find() to invoke the Boyer-Moore matching algorithm for finding of needle in a given haystack.auto bmFinder = boyerMooreFinder("TG");
string r = "TAGTGCCTGA";
// search for the first match in the haystack r
r = bmFinder.beFound(r);
writeln(r); // "TGCCTGA"
// continue search in haystack
r = bmFinder.beFound(r[2 .. $]);
writeln(r); // "TGA"
Returns the common prefix of two ranges.
| pred | The predicate to use in comparing elements for commonality. Defaults to equality "a == b". |
R1 r1
| A forward range of elements. |
R2 r2
| An input range of elements. |
r1 which contains the characters that both ranges start with, if the first argument is a string; otherwise, the same as the result of takeExactly(r1, n), where n is the number of elements in the common prefix of both ranges. std.range.takeExactlywriteln(commonPrefix("hello, world", "hello, there")); // "hello, "
The first version counts the number of elements x in r for which pred(x, value) is true. pred defaults to equality. Performs Ο(haystack.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(haystack.length) evaluations of pred.
The fourth version counts the number of elements in a range. It is an optimization for the third version: if the given range has the length property the count is returned right away, otherwise performs Ο(haystack.length) to walk the range.
count will not accept infinite ranges for haystack. | pred | The predicate to evaluate. |
Range haystack
| The range to count. |
E needle
| The element or sub-range to count in the haystack. |
haystack for which pred returned true.import std.uni : toLower;
// count elements in range
int[] a = [ 1, 2, 4, 3, 2, 5, 3, 2, 4 ];
writeln(count(a)); // 9
writeln(count(a, 2)); // 3
writeln(count!("a > b")(a, 2)); // 5
// count range in range
writeln(count("abcadfabf", "ab")); // 2
writeln(count("ababab", "abab")); // 1
writeln(count("ababab", "abx")); // 0
// fuzzy count range in range
writeln(count!( (a, b) => toLower(a) == toLower(b))("AbcAdFaBf", "ab")); // 2
// count predicate in range
writeln(count!("a > 1")(a)); // 8
Counts elements in the given forward range until the given predicate is true for one of the given needles.
| pred | The predicate for determining when to stop counting. |
R haystack
| The input range to be counted. |
Rs needles
| Either a single element, or a forward range of elements, to be evaluated in turn against each element in haystack under the given predicate. |
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. If only pred is provided, pred(haystack) is tested for each element. std.string.indexOfwriteln(countUntil("hello world", "world")); // 6
writeln(countUntil("hello world", 'r')); // 8
writeln(countUntil("hello world", "programming")); // -1
writeln(countUntil("日本語", "本語")); // 1
writeln(countUntil("日本語", '語')); // 2
writeln(countUntil("日本語", "五")); // -1
writeln(countUntil("日本語", '五')); // -1
writeln(countUntil([0, 7, 12, 22, 9], [12, 22])); // 2
writeln(countUntil([0, 7, 12, 22, 9], 9)); // 4
writeln(countUntil!"a > b"([0, 7, 12, 22, 9], 20)); // 3
import std.ascii : isDigit;
import std.uni : isWhite;
writeln(countUntil!(std.uni.isWhite)("hello world")); // 5
writeln(countUntil!(std.ascii.isDigit)("hello world")); // -1
writeln(countUntil!"a > 20"([0, 7, 12, 22, 9])); // 3
Checks if the given range ends with (one of) the given needle(s). The reciprocal of startsWith.
| pred | The predicate to use for comparing elements between the range and the needle(s). |
Range doesThisEnd
| The bidirectional range to check. |
Needles withOneOfThese
| The needles to check against, which may be single elements, or bidirectional ranges of elements. |
R2 withThis
| The single element to check. |
withOneOfThese[0], 2 if it ends with withOneOfThese[1], and so on. In the case when no needle parameters are given, return true iff back of doesThisStart fulfils predicate pred.import std.ascii : isAlpha;
assert("abc".endsWith!(a => a.isAlpha));
assert("abc".endsWith!isAlpha);
assert(!"ab1".endsWith!(a => a.isAlpha));
assert(!"ab1".endsWith!isAlpha);
assert(!"".endsWith!(a => a.isAlpha));
import std.algorithm.comparison : among;
assert("abc".endsWith!(a => a.among('c', 'd') != 0));
assert(!"abc".endsWith!(a => a.among('a', 'b') != 0));
assert(endsWith("abc", ""));
assert(!endsWith("abc", "b"));
writeln(endsWith("abc", "a", 'c')); // 2
writeln(endsWith("abc", "c", "a")); // 1
writeln(endsWith("abc", "c", "c")); // 1
writeln(endsWith("abc", "bc", "c")); // 2
writeln(endsWith("abc", "x", "c", "b")); // 2
writeln(endsWith("abc", "x", "aa", "bc")); // 3
writeln(endsWith("abc", "x", "aaa", "sab")); // 0
writeln(endsWith("abc", "x", "aaa", 'c', "sab")); // 3
Finds an individual element in an input range. Elements of haystack are compared with needle by using predicate pred with pred(haystack.front, needle). find performs Ο(walkLength(haystack)) evaluations of pred.
The predicate is passed to std.functional.binaryFun, and can either accept a string, or any callable that can be executed via pred(element, element).
To find the last occurrence of needle in a bidirectional haystack, call find(retro(haystack), needle). See std.range.retro.
If no needle is provided, pred(haystack.front) will be evaluated on each element of the input range.
If input is a forward range, needle can be a forward range too. In this case startsWith!pred(haystack, needle) is evaluated on each evaluation.
find behaves similar to dropWhile in other languages. find performs Ο(walkLength(haystack)) evaluations of pred. There are specializations that improve performance by taking advantage of bidirectional or random access ranges (where possible). | pred | The predicate for comparing each element with the needle, defaulting to equality "a == b". The negated predicate "a != b" can be used to search instead for the first element not matching the needle. |
InputRange haystack
| The input range searched in. |
Element needle
| The element searched for. |
haystack advanced such that the front element is the one searched for; that is, until binaryFun!pred(haystack.front, needle) is true. If no such position exists, returns an empty haystack. findAdjacent, findAmong, findSkip, findSplit, startsWith
import std.range.primitives;
auto arr = [1, 2, 4, 4, 4, 4, 5, 6, 9];
writeln(arr.find(4)); // [4, 4, 4, 4, 5, 6, 9]
writeln(arr.find(1)); // arr
writeln(arr.find(9)); // [9]
writeln(arr.find!( (a, b) => a > b)(4)); // [5, 6, 9]
writeln(arr.find!( (a, b) => a < b)(4)); // arr
assert(arr.find(0).empty);
assert(arr.find(10).empty);
assert(arr.find(8).empty);
writeln(find("hello, world", ',')); // ", world"
import std.range.primitives;
import std.uni : toLower;
string[] s = ["Hello", "world", "!"];
writeln(s.find!( (a, b) => toLower(a) == b)("hello")); // s
auto arr = [ 1, 2, 3, 4, 1 ];
writeln(find!("a > 2")(arr)); // [3, 4, 1]
// with predicate alias
bool pred(int x) { return x + 1 > 1.5; }
writeln(find!(pred)(arr)); // arr
import std.container : SList;
import std.range.primitives : empty;
import std.typecons : Tuple;
assert(find("hello, world", "World").empty);
writeln(find("hello, world", "wo")); // "world"
writeln([1, 2, 3, 4].find(SList!int(2, 3)[])); // [2, 3, 4]
alias C = Tuple!(int, "x", int, "y");
auto a = [C(1,0), C(2,0), C(3,1), C(4,0)];
writeln(a.find!"a.x == b"([2, 3])); // [C(2, 0), C(3, 1), C(4, 0)]
writeln(a[1 .. $].find!"a.x == b"([2, 3])); // [C(2, 0), C(3, 1), C(4, 0)]
Finds two or more needles into a haystack. The predicate pred is used throughout to compare elements. By default, elements are compared for equality.
| pred | The predicate to use for comparing elements. |
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. |
haystack positioned to match one of the needles and also the 1-based index of the matching element in needles (0 if none of needles matched, 1 if needles[0] matched, 2 if needles[1] matched...). The first needle to be found will be the one that matches. If multiple needles are found at the same spot in the range, then the shortest one is the one which matches (if multiple needles of the same length are found at the same spot (e.g "a" and 'a'), then the left-most of them in the argument list matches). The relationship between haystack and needles simply means that one can e.g. search for individual ints or arrays of ints in an array of ints. In addition, if elements are individually comparable, searches of heterogeneous types are allowed as well: a double[] can be searched for an int or a short[], and conversely a long can be searched for a float or a double[]. This makes for efficient searches without the need to coerce one side of the comparison into the other's side type. The complexity of the search is Ο(haystack.length * max(needles.length)). (For needles that are individual items, length is considered to be 1.) The strategy used in searching several subranges at once maximizes cache usage by moving in haystack as few times as possible.import std.typecons : tuple; int[] a = [ 1, 4, 2, 3 ]; writeln(find(a, 4)); // [4, 2, 3] writeln(find(a, [1, 4])); // [1, 4, 2, 3] writeln(find(a, [1, 3], 4)); // tuple([4, 2, 3], 2) // Mixed types allowed if comparable writeln(find(a, 5, [1.2, 3.5], 2.0)); // tuple([2, 3], 3)
Finds needle in haystack efficiently using the Boyer-Moore method.
RandomAccessRange haystack
| A random-access range with length and slicing. |
BoyerMooreFinder!(pred, InputRange) needle
| A BoyerMooreFinder. |
haystack advanced such that needle is a prefix of it (if no such position exists, returns haystack advanced to termination).import std.range.primitives : empty; int[] a = [ -1, 0, 1, 2, 3, 4, 5 ]; int[] b = [ 1, 2, 3 ]; writeln(find(a, boyerMooreFinder(b))); // [1, 2, 3, 4, 5] assert(find(b, boyerMooreFinder(a)).empty);
Convenience function. Like find, but only returns whether or not the search was successful.
std.algorithm.comparison.among for checking a value against multiple possibilities.writeln(canFind([0, 1, 2, 3], 2)); // true assert(canFind([0, 1, 2, 3], [1, 2], [2, 3])); writeln(canFind([0, 1, 2, 3], [1, 2], [2, 3])); // 1 assert(canFind([0, 1, 2, 3], [1, 7], [2, 3])); writeln(canFind([0, 1, 2, 3], [1, 7], [2, 3])); // 2 writeln(canFind([0, 1, 2, 3], 4)); // false assert(!canFind([0, 1, 2, 3], [1, 3], [2, 4])); writeln(canFind([0, 1, 2, 3], [1, 3], [2, 4])); // 0
auto words = [
"apple",
"beeswax",
"cardboard"
];
assert(!canFind(words, "bees"));
assert( canFind!((string a, string b) => a.startsWith(b))(words, "bees"));
Returns true if and only if any value v found in the input range range satisfies the predicate pred. Performs (at most) Ο(haystack.length) evaluations of pred.
Returns true if and only if needle can be found in range. Performs Ο(haystack.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.
Advances r until it finds the first two adjacent elements a, b that satisfy pred(a, b). Performs Ο(r.length) evaluations of pred.
| pred | The predicate to satisfy. |
Range r
| A forward range to search in. |
r advanced to the first occurrence of two adjacent elements that satisfy the given predicate. If there are no such two elements, returns r advanced until empty. adjacent_findint[] a = [ 11, 10, 10, 9, 8, 8, 7, 8, 9 ];
auto r = findAdjacent(a);
writeln(r); // [10, 10, 9, 8, 8, 7, 8, 9]
auto p = findAdjacent!("a < b")(a);
writeln(p); // [7, 8, 9]
Searches the given range for an element that matches one of the given choices.
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.
| pred | The predicate to use for determining a match. |
InputRange seq
| The input range to search. |
ForwardRange choices
| A forward range of possible choices. |
seq advanced to the first matching element, or until empty if there are no matching elements. find, algorithm.comparison.among.std
int[] a = [ -1, 0, 1, 2, 3, 4, 5 ]; int[] b = [ 3, 1, 2 ]; writeln(findAmong(a, b)); // a[2 .. $]
Finds needle in haystack and positions haystack right after the first occurrence of needle.
If no needle is provided, the haystack is advanced as long as pred evaluates to true. Similarly, the haystack is positioned so as pred evaluates to false for haystack.front.
R1 haystack
| The forward range to search in. |
R2 needle
| The forward range to search for. |
| pred | Custom predicate for comparison of haystack and needle |
true if the needle was found, in which case haystack is positioned after the end of the first occurrence of needle; otherwise false, leaving haystack untouched. If no needle is provided, it returns the number of times pred(haystack.front) returned true. findimport std.range.primitives : empty; // Needle is found; s is replaced by the substring following the first // occurrence of the needle. string s = "abcdef"; assert(findSkip(s, "cd") && s == "ef"); // Needle is not found; s is left untouched. s = "abcdef"; assert(!findSkip(s, "cxd") && s == "abcdef"); // If the needle occurs at the end of the range, the range is left empty. s = "abcdef"; assert(findSkip(s, "def") && s.empty);
import std.ascii : isWhite; string s = " abc"; assert(findSkip!isWhite(s) && s == "abc"); assert(!findSkip!isWhite(s) && s == "abc"); s = " "; writeln(findSkip!isWhite(s)); // 2
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.
| pred | Predicate to use for comparing needle against haystack. |
R1 haystack
| The range to search. |
R2 needle
| What to look for. |
Tuple!() of the split portions of haystack (see above for details). This sub-type of Tuple!() has opCast defined for bool. This opCast returns true when the separating needle was found and false otherwise. findstd.typecons.Tuple enables the following convenient idiom: // findSplit returns a triplet
if (auto split = "dlang-rocks".findSplit("-"))
writeln(split[2]); // "rocks"
import std.range.primitives : empty; auto a = "Carl Sagan Memorial Station"; auto r = findSplit(a, "Velikovsky"); import std.typecons : isTuple; static assert(isTuple!(typeof(r.asTuple))); static assert(isTuple!(typeof(r))); assert(!r); writeln(r[0]); // a assert(r[1].empty); assert(r[2].empty); r = findSplit(a, " "); writeln(r[0]); // "Carl" writeln(r[1]); // " " writeln(r[2]); // "Sagan Memorial Station" auto r1 = findSplitBefore(a, "Sagan"); assert(r1); writeln(r1[0]); // "Carl " writeln(r1[1]); // "Sagan Memorial Station" auto r2 = findSplitAfter(a, "Sagan"); assert(r2); writeln(r2[0]); // "Carl Sagan" writeln(r2[1]); // " Memorial Station"
std.range.only to find single elements: import std.range : only; writeln([1, 2, 3, 4].findSplitBefore(only(3))[0]); // [1, 2]
Computes the minimum (respectively maximum) of range along with its number of occurrences. Formally, the minimum is a value x in range such that pred(a, x) is false for all values a in range. Conversely, the maximum is a value x in range such that pred(x, a) is false for all values a in range (note the swapped arguments to pred).
These functions may be used for computing arbitrary extrema by choosing pred appropriately. For corrrect functioning, pred must be a strict partial order, i.e. transitive (if pred(a, b) && pred(b, c) then pred(a, c)) and irreflexive (pred(a, a) is false). The trichotomy property of inequality is not required: these algoritms consider elements a and b equal (for the purpose of counting) if pred puts them in the same equivalence class, i.e. !pred(a, b) && !pred(b, a).
| pred | The ordering predicate to use to determine the extremum (minimum or maximum). |
Range range
| The input range to count. |
Exception if range.empty. std.algorithm.comparison.min, minIndex, minElement, minPos
import std.conv : text; import std.typecons : tuple; int[] a = [ 2, 3, 4, 1, 2, 4, 1, 1, 2 ]; // Minimum is 1 and occurs 3 times writeln(a.minCount); // tuple(1, 3) // Maximum is 4 and occurs 2 times writeln(a.maxCount); // tuple(4, 2)
Iterates the passed range and returns the minimal element. A custom mapping function can be passed to map. In other languages this is sometimes called argmin.
n - 1 comparisons are needed. | map | custom accessor for the comparison key |
Range r
| range from which the minimal element will be selected |
RangeElementType seed
| custom seed to use as initial element |
maxElement, std.algorithm.comparison.min, minCount, minIndex, minPos
import std.range : enumerate; import std.typecons : tuple; writeln([2, 7, 1, 3].minElement); // 1 // allows to get the index of an element too writeln([5, 3, 7, 9].enumerate.minElement!"a.value"); // tuple(1, 3) // any custom accessor can be passed writeln([[0, 4], [1, 2]].minElement!"a[1]"); // [1, 2] // can be seeded int[] arr; writeln(arr.minElement(1)); // 1
Iterates the passed range and returns the maximal element. A custom mapping function can be passed to map. In other languages this is sometimes called argmax.
n - 1 comparisons are needed. | map | custom accessor for the comparison key |
Range r
| range from which the maximum will be selected |
RangeElementType seed
| custom seed to use as initial element |
minElement, std.algorithm.comparison.max, maxCount, maxIndex, maxPos
import std.range : enumerate; import std.typecons : tuple; writeln([2, 1, 4, 3].maxElement); // 4 // allows to get the index of an element too writeln([2, 1, 4, 3].enumerate.maxElement!"a.value"); // tuple(2, 4) // any custom accessor can be passed writeln([[0, 4], [1, 2]].maxElement!"a[1]"); // [0, 4] // can be seeded int[] arr; writeln(arr.minElement(1)); // 1
Computes a subrange of range starting at the first occurrence of range's minimum (respectively maximum) and with the same ending as range, or the empty range if range itself is empty.
Formally, the minimum is a value x in range such that pred(a, x) is false for all values a in range. Conversely, the maximum is a value x in range such that pred(x, a) is false for all values a in range (note the swapped arguments to pred).
These functions may be used for computing arbitrary extrema by choosing pred appropriately. For corrrect functioning, pred must be a strict partial order, i.e. transitive (if pred(a, b) && pred(b, c) then pred(a, c)) and irreflexive (pred(a, a) is false).
| pred | The ordering predicate to use to determine the extremum (minimum or maximum) element. |
Range range
| The input range to search. |
range, i.e. a subrange of range starting at the position of its smallest (respectively largest) element and with the same ending as range. std.algorithm.comparison.max, minCount, minIndex, minElement
int[] a = [ 2, 3, 4, 1, 2, 4, 1, 1, 2 ]; // Minimum is 1 and first occurs in position 3 writeln(a.minPos); // [1, 2, 4, 1, 1, 2] // Maximum is 4 and first occurs in position 2 writeln(a.maxPos); // [4, 1, 2, 4, 1, 1, 2]
Computes the index of the first occurrence of range's minimum element.
| pred | The ordering predicate to use to determine the minimum element. |
Range range
| The input range to search. |
range.length) Exactly range.length - 1 comparisons are needed. range. If the range is empty, -1 is returned. maxIndex, std.algorithm.comparison.min, minCount, minElement, minPos
int[] a = [2, 3, 4, 1, 2, 4, 1, 1, 2];
// Minimum is 1 and first occurs in position 3
writeln(a.minIndex); // 3
// Get maximum index with minIndex
writeln(a.minIndex!"a > b"); // 2
// Range is empty, so return value is -1
int[] b;
writeln(b.minIndex); // -1
// Works with more custom types
struct Dog { int age; }
Dog[] dogs = [Dog(10), Dog(5), Dog(15)];
writeln(dogs.minIndex!"a.age < b.age"); // 1
Computes the index of the first occurrence of range's maximum element.
range) Exactly range.length - 1 comparisons are needed. | pred | The ordering predicate to use to determine the maximum element. |
Range range
| The input range to search. |
range. If the range is empty, -1 is returned. minIndex, std.algorithm.comparison.max, maxCount, maxElement, maxPos
// Maximum is 4 and first occurs in position 2
int[] a = [2, 3, 4, 1, 2, 4, 1, 1, 2];
writeln(a.maxIndex); // 2
// Empty range
int[] b;
writeln(b.maxIndex); // -1
// Works with more custom types
struct Dog { int age; }
Dog[] dogs = [Dog(10), Dog(15), Dog(5)];
writeln(dogs.maxIndex!"a.age < b.age"); // 1
Skip over the initial portion of the first given range (haystack) that matches any of the additionally given ranges (needles) fully, or if no second range is given skip over the elements that fulfill pred. Do nothing if there is no match.
| pred | The predicate that determines whether elements from each respective range match. Defaults to equality "a == b". |
import std.algorithm.comparison : equal; auto s1 = "Hello world"; assert(!skipOver(s1, "Ha")); writeln(s1); // "Hello world" assert(skipOver(s1, "Hell") && s1 == "o world", s1); string[] r1 = ["abc", "def", "hij"]; dstring[] r2 = ["abc"d]; assert(!skipOver!((a, b) => a.equal(b))(r1, ["def"d]), r1[0]); writeln(r1); // ["abc", "def", "hij"] assert(skipOver!((a, b) => a.equal(b))(r1, r2)); writeln(r1); // ["def", "hij"]
import std.ascii : isWhite; import std.range.primitives : empty; auto s2 = "\t\tvalue"; auto s3 = ""; auto s4 = "\t\t\t"; assert(s2.skipOver!isWhite && s2 == "value"); assert(!s3.skipOver!isWhite); assert(s4.skipOver!isWhite && s3.empty);
auto s = "Hello world"; assert(!skipOver(s, "hello", "HellO")); writeln(s); // "Hello world" // the range is skipped over the longest matching needle is skipped assert(skipOver(s, "foo", "hell", "Hello ")); writeln(s); // "world"
import std.algorithm.comparison : equal;
auto s1 = "Hello world";
assert(!skipOver(s1, 'a'));
writeln(s1); // "Hello world"
assert(skipOver(s1, 'H') && s1 == "ello world");
string[] r = ["abc", "def", "hij"];
dstring e = "abc"d;
assert(!skipOver!((a, b) => a.equal(b))(r, "def"d));
writeln(r); // ["abc", "def", "hij"]
assert(skipOver!((a, b) => a.equal(b))(r, e));
writeln(r); // ["def", "hij"]
auto s2 = "";
assert(!s2.skipOver('a'));
import std.ascii : isWhite; import std.range.primitives : empty; alias whitespaceSkiper = skipOver!isWhite; auto s2 = "\t\tvalue"; auto s3 = ""; auto s4 = "\t\t\t"; assert(whitespaceSkiper(s2) && s2 == "value"); assert(!whitespaceSkiper(s2)); assert(whitespaceSkiper(s4) && s3.empty);
Haystack haystack
| The forward range to move forward. |
Needles needles
| The input ranges representing the prefix of r1 to skip over. |
Es es
| The element to match. |
true if the prefix of haystack matches any range of needles fully or pred evaluates to true, and haystack has been advanced to the point past this segment; otherwise false, and haystack is left in its original position. needles contains an empty range, skipOver will return true.Checks whether the given input range starts with (one of) the given needle(s) or, if no needles are given, if its front element fulfils predicate pred.
| pred | Predicate to use in comparing the elements of the haystack and the needle(s). Mandatory if no needles are given. |
Range doesThisStart
| The input range to check. |
Needles withOneOfThese
| The needles against which the range is to be checked, which may be individual elements or input ranges of elements. |
R2 withThis
| The single needle to check, which may be either a single element or an input range of elements. |
withOneOfThese[0], 2 if it starts with withOneOfThese[1], and so on. 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). In the case when no needle parameters are given, return true iff front of doesThisStart fulfils predicate pred.import std.ascii : isAlpha;
assert("abc".startsWith!(a => a.isAlpha));
assert("abc".startsWith!isAlpha);
assert(!"1ab".startsWith!(a => a.isAlpha));
assert(!"".startsWith!(a => a.isAlpha));
import std.algorithm.comparison : among;
assert("abc".startsWith!(a => a.among('a', 'b') != 0));
assert(!"abc".startsWith!(a => a.among('b', 'c') != 0));
assert(startsWith("abc", ""));
assert(startsWith("abc", "a"));
assert(!startsWith("abc", "b"));
writeln(startsWith("abc", 'a', "b")); // 1
writeln(startsWith("abc", "b", "a")); // 2
writeln(startsWith("abc", "a", "a")); // 1
writeln(startsWith("abc", "ab", "a")); // 2
writeln(startsWith("abc", "x", "a", "b")); // 2
writeln(startsWith("abc", "x", "aa", "ab")); // 3
writeln(startsWith("abc", "x", "aaa", "sab")); // 0
writeln(startsWith("abc", "x", "aaa", "a", "sab")); // 3
import std.typecons : Tuple;
alias C = Tuple!(int, "x", int, "y");
assert(startsWith!"a.x == b"([ C(1,1), C(1,2), C(2,2) ], [1, 1]));
writeln(startsWith!"a.x == b"([C(1, 1), C(2, 1), C(2, 2)], [1, 1], [1, 2], [1, 3])); // 2
Interval option specifier for until (below) and others.
If set to OpenRight.yes, then the interval is open to the right (last element is not included).
Otherwise if set to OpenRight.no, then the interval is closed to the right (last element included).
Lazily iterates range until the element e for which pred(e, sentinel) is true.
This is similar to takeWhile in other languages.
| pred | Predicate to determine when to stop. |
Range range
| The input range to iterate over. |
Sentinel sentinel
| The element to stop at. |
OpenRight openRight
| Determines whether the element for which the given predicate is true should be included in the resulting range (No.openRight), or not (Yes.openRight). |
import std.algorithm.comparison : equal; import std.typecons : No; 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, No.openRight), [1, 2, 4, 7]));
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