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# std.algorithm.searching

This is a submodule of std.algorithm. It contains generic searching algorithms.

Cheat Sheet
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.
mismatch | mismatch("parakeet", "parachute") returns the two ranges "keet" and "chute".
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.

License:
Boost License 1.0.
Authors:
Andrei Alexandrescu

Source std/algorithm/searching.d

template `all`(alias pred = "a")
  Checks if all of the elements verify pred.
  Examples:

      assert( all!"a & 1"([1, 3, 5, 7, 9]));
      assert(!all!"a & 1"([1, 2, 3, 5, 7, 9]));

  Examples:
  `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[]));

  bool `all`(Range)(Range `range`)
  if (isInputRange!Range && is(typeof(unaryFun!pred(`range`.front))));
    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.
template `any`(alias pred = "a")
  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.
  Examples:

      import std.ascii : isWhite;
      assert( all!(any!isWhite)(["a a", "b b"]));
      assert(!any!(all!isWhite)(["a a", "b b"]));

  Examples:
  `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[]));

  bool `any`(Range)(Range `range`)
  if (isInputRange!Range && is(typeof(unaryFun!pred(`range`.front))));
    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.
bool `balancedParens`(Range, E)(Range `r`, E `lPar`, E `rPar`, size_t `maxNestingLevel` = size_t.max)
if (isInputRange!Range && is(typeof(`r`.front == `lPar`)));
  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.
  Parameters:

  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.

  Returns:
  `true` if the given range has balanced parenthesis within the given maximum nesting level; `false` otherwise.
  Examples:

      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));

struct `BoyerMooreFinder`(alias pred, Range);
BoyerMooreFinder!(binaryFun!pred, Range) `boyerMooreFinder`(alias pred = "a == b", Range)(Range `needle`)
if (isRandomAccessRange!Range && hasSlicing!Range || isSomeString!Range);
  Sets up Boyer-Moore matching for use with find below. By default, elements are compared for equality.
  `BoyerMooreFinder` allocates GC memory.
  Parameters:

  pred | Predicate used to compare elements.
  Range `needle` | A random-access range with length and slicing.

  Returns:
  An instance of `BoyerMooreFinder` that can be used with find() to invoke the Boyer-Moore matching algorithm for finding of `needle` in a given haystack.
  Examples:

      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"

  this(Range `needle`);
  Range `beFound`(Range `haystack`);
  @property size_t `length`();
  alias `opDollar` = length;
auto `commonPrefix`(alias pred = "a == b", R1, R2)(R1 `r1`, R2 `r2`)
if (isForwardRange!R1 && isInputRange!R2 && !isNarrowString!R1 && is(typeof(binaryFun!pred(`r1`.front, `r2`.front))));
auto `commonPrefix`(alias pred, R1, R2)(R1 `r1`, R2 `r2`)
if (isNarrowString!R1 && isInputRange!R2 && is(typeof(binaryFun!pred(`r1`.front, `r2`.front))));
auto `commonPrefix`(R1, R2)(R1 `r1`, R2 `r2`)
if (isNarrowString!R1 && isInputRange!R2 && !isNarrowString!R2 && is(typeof(`r1`.front == `r2`.front)));
auto `commonPrefix`(R1, R2)(R1 `r1`, R2 `r2`)
if (isNarrowString!R1 && isNarrowString!R2);
  Returns the common prefix of two ranges.
  Parameters:

  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.

  Returns:
  A slice of `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.
  See Also:
  std.range.takeExactly
  Examples:

      writeln(commonPrefix("hello, world", "hello, there")); // "hello, "

size_t `count`(alias pred = "a == b", Range, E)(Range `haystack`, E `needle`)
if (isInputRange!Range && !isInfinite!Range && is(typeof(binaryFun!pred(`haystack`.front, `needle`)) : bool));
size_t `count`(alias pred = "a == b", R1, R2)(R1 `haystack`, R2 `needle`)
if (isForwardRange!R1 && !isInfinite!R1 && isForwardRange!R2 && is(typeof(binaryFun!pred(`haystack`.front, `needle`.front)) : bool));
size_t `count`(alias pred, R)(R `haystack`)
if (isInputRange!R && !isInfinite!R && is(typeof(unaryFun!pred(`haystack`.front)) : bool));
size_t `count`(R)(R `haystack`)
if (isInputRange!R && !isInfinite!R);
  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.

  Note Regardless of the overload, `count` will not accept infinite ranges for `haystack`.

  Parameters:

  pred | The predicate to evaluate.
  Range `haystack` | The range to count.
  E `needle` | The element or sub-range to count in the `haystack`.

  Returns:
  The number of positions in the `haystack` for which pred returned `true`.
  Examples:

      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

ptrdiff_t `countUntil`(alias pred = "a == b", R, Rs...)(R `haystack`, Rs `needles`)
if (isForwardRange!R && (Rs.length > 0) && (isForwardRange!(Rs[0]) == isInputRange!(Rs[0])) && is(typeof(startsWith!pred(`haystack`, `needles`[0]))) && (Rs.length == 1 || is(typeof(`countUntil`!pred(`haystack`, `needles`[1..$])))));
ptrdiff_t `countUntil`(alias pred = "a == b", R, N)(R `haystack`, N `needle`)
if (isInputRange!R && is(typeof(binaryFun!pred(`haystack`.front, `needle`)) : bool));
  Counts elements in the given forward range until the given predicate is `true` for one of the given `needles`.
  Parameters:

  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.

  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.
  See Also:
  std.string.indexOf
  Examples:

      writeln(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

ptrdiff_t `countUntil`(alias pred, R)(R `haystack`)
if (isInputRange!R && is(typeof(unaryFun!pred(`haystack`.front)) : bool));
  Similar to the previous overload of `countUntil`, except that this one evaluates only the predicate pred.
  Parameters:

  pred | Predicate to when to stop counting.
  R `haystack` | An input range of elements to be counted.

  Returns:
  The number of elements which must be popped from `haystack` before pred(`haystack`.front) is `true`.
  Examples:

      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

uint `endsWith`(alias pred = "a == b", Range, Needles...)(Range `doesThisEnd`, Needles `withOneOfThese`)
if (isBidirectionalRange!Range && (Needles.length > 1) && is(typeof(.`endsWith`!pred(`doesThisEnd`, `withOneOfThese`[0])) : bool) && is(typeof(.`endsWith`!pred(`doesThisEnd`, `withOneOfThese`[1..$])) : uint));
bool `endsWith`(alias pred = "a == b", R1, R2)(R1 `doesThisEnd`, R2 `withThis`)
if (isBidirectionalRange!R1 && isBidirectionalRange!R2 && is(typeof(binaryFun!pred(`doesThisEnd`.back, `withThis`.back)) : bool));
bool `endsWith`(alias pred = "a == b", R, E)(R `doesThisEnd`, E `withThis`)
if (isBidirectionalRange!R && is(typeof(binaryFun!pred(`doesThisEnd`.back, `withThis`)) : bool));
bool `endsWith`(alias pred, R)(R `doesThisEnd`)
if (isInputRange!R && ifTestable!(typeof(`doesThisEnd`.front), unaryFun!pred));
  Checks if the given range ends with (one of) the given needle(s). The reciprocal of startsWith.
  Parameters:

  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.

  Returns:
  0 if the needle(s) do not occur at the end of the given range; otherwise the position of the matching needle, that is, 1 if the range ends with `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.
  Examples:

      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

InputRange `find`(alias pred = "a == b", InputRange, Element)(InputRange `haystack`, scope Element `needle`)
if (isInputRange!InputRange && is(typeof(binaryFun!pred(`haystack`.front, `needle`)) : bool));
  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.
  To find the last occurrence of `needle` in `haystack`, call `find`(retro(`haystack`), `needle`). See std.range.retro.
  Parameters:

  pred | The predicate for comparing each element with the `needle`, defaulting to "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.

  Constraints isInputRange!InputRange && is(typeof(binaryFun!pred(`haystack`.front, `needle`) : bool))

  Returns:
  `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`.
  See Also:
  STL's find
  Examples:

      import std.algorithm.comparison : equal;
      import std.container : SList;
      import std.range;
      import std.range.primitives : empty;

      auto arr = assumeSorted!"a < b"([1, 2, 4, 4, 4, 4, 5, 6, 9]);
      writeln(find(arr, 4)); // assumeSorted!"a < b"([4, 4, 4, 4, 5, 6, 9])
      writeln(find(arr, 1)); // arr
      writeln(find(arr, 9)); // assumeSorted!"a < b"([9])
      writeln(find!"a > b"(arr, 4)); // assumeSorted!"a < b"([5, 6, 9])
      writeln(find!"a < b"(arr, 4)); // arr
      assert(find(arr, 0).empty());
      assert(find(arr, 10).empty());
      assert(find(arr, 8).empty());

      auto r = assumeSorted!"a > b"([10, 7, 3, 1, 0, 0]);
      writeln(find(r, 3)); // assumeSorted!"a > b"([3, 1, 0, 0])
      writeln(find!"a > b"(r, 8)); // r
      writeln(find!"a < b"(r, 5)); // assumeSorted!"a > b"([3, 1, 0, 0])

      writeln(find("hello, world", ',')); // ", world"
      writeln(find([1, 2, 3, 5], 4)); // []
      assert(equal(find(SList!int(1, 2, 3, 4, 5)[], 4), SList!int(4, 5)[]));
      writeln(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);

InputRange `find`(alias pred, InputRange)(InputRange `haystack`)
if (isInputRange!InputRange);
  Advances the input range `haystack` by calling `haystack`.popFront until either pred(`haystack`.front), or `haystack`.empty. Performs Ο(`haystack`.length) evaluations of pred.
  To find the last element of a bidirectional `haystack` satisfying pred, call `find`!(pred)(retro(`haystack`)). See std.range.retro.
  `find` behaves similar to dropWhile in other languages.
  Parameters:

  pred | The predicate for determining if a given element is the one being searched for.
  InputRange `haystack` | The input range to search in.

  Returns:
  `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`.
  See Also:
  STL's find_if
  Examples:

      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

R1 `find`(alias pred = "a == b", R1, R2)(R1 `haystack`, scope R2 `needle`)
if (isForwardRange!R1 && isForwardRange!R2 && is(typeof(binaryFun!pred(`haystack`.front, `needle`.front)) : bool));
  Finds the first occurrence of a forward range in another forward range.
  Performs Ο(walkLength(`haystack`) * walkLength(`needle`)) comparisons in the worst case. There are specializations that improve performance by taking advantage of bidirectional range or random access in the given ranges (where possible), depending on the statistics of the two ranges' content.
  Parameters:

  pred | The predicate to use for comparing respective elements from the `haystack` and the `needle`. Defaults to simple equality "a == b".
  R1 `haystack` | The forward range searched in.
  R2 `needle` | The forward range searched for.

  Returns:
  `haystack` advanced such that `needle` is a prefix of it (if no such position exists, returns `haystack` advanced to termination).
  Examples:

      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)]

Tuple!(Range, size_t) `find`(alias pred = "a == b", Range, Ranges...)(Range `haystack`, Ranges `needles`)
if (Ranges.length > 1 && is(typeof(startsWith!pred(`haystack`, `needles`))));
  Finds two or more `needles` into a `haystack`. The predicate pred is used throughout to compare elements. By default, elements are compared for equality.
  Parameters:

  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`.

  Returns:
  A tuple containing `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.
  Examples:

      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)

RandomAccessRange `find`(RandomAccessRange, alias pred, InputRange)(RandomAccessRange `haystack`, scope BoyerMooreFinder!(pred, InputRange) `needle`);
  Finds `needle` in `haystack` efficiently using the Boyer-Moore method.
  Parameters:

  RandomAccessRange `haystack` | A random-access range with length and slicing.
  BoyerMooreFinder!(pred, InputRange) `needle` | A BoyerMooreFinder.

  Returns:
  `haystack` advanced such that `needle` is a prefix of it (if no such position exists, returns `haystack` advanced to termination).
  Examples:

      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);

template `canFind`(alias pred = "a == b")
  Convenience function. Like find, but only returns whether or not the search was successful.
  See Also:
  std.algorithm.comparison.among for checking a value against multiple possibilities.
  Examples:

      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

  Examples:
  Example using a custom predicate. Note that the needle appears as the second argument of the predicate.

      auto words = [
          "apple",
          "beeswax",
          "cardboard"
      ];
      assert(!canFind(words, "bees"));
      assert( canFind!((string a, string b) => a.startsWith(b))(words, "bees"));

  bool `canFind`(Range)(Range `haystack`)
  if (is(typeof(find!pred(`haystack`))));
    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.
  bool `canFind`(Range, Element)(Range `haystack`, scope Element `needle`)
  if (is(typeof(find!pred(`haystack`, `needle`))));
    Returns `true` if and only if `needle` can be found in range. Performs Ο(`haystack`.length) evaluations of pred.
  size_t `canFind`(Range, Ranges...)(Range `haystack`, scope Ranges `needles`)
  if (Ranges.length > 1 && allSatisfy!(isForwardRange, Ranges) && is(typeof(find!pred(`haystack`, `needles`))));
    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.
Range `findAdjacent`(alias pred = "a == b", Range)(Range `r`)
if (isForwardRange!Range);
  Advances `r` until it finds the first two adjacent elements a, b that satisfy pred(a, b). Performs Ο(`r`.length) evaluations of pred.
  Parameters:

  pred | The predicate to satisfy.
  Range `r` | A forward range to search in.

  Returns:
  `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.
  See Also:
  STL's adjacent_find
  Examples:

      int[] 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]

InputRange `findAmong`(alias pred = "a == b", InputRange, ForwardRange)(InputRange `seq`, ForwardRange `choices`)
if (isInputRange!InputRange && isForwardRange!ForwardRange);
  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.
  Parameters:

  pred | The predicate to use for determining a match.
  InputRange `seq` | The input range to search.
  ForwardRange `choices` | A forward range of possible `choices`.

  Returns:
  `seq` advanced to the first matching element, or until empty if there are no matching elements.
  See Also:
  STL's find_first_of
  Examples:

      int[] a = [ -1, 0, 1, 2, 3, 4, 5 ];
      int[] b = [ 3, 1, 2 ];
      writeln(findAmong(a, b)); // a[2 .. $]

bool `findSkip`(alias pred = "a == b", R1, R2)(ref R1 `haystack`, R2 `needle`)
if (isForwardRange!R1 && isForwardRange!R2 && is(typeof(binaryFun!pred(`haystack`.front, `needle`.front))));
  Finds `needle` in `haystack` and positions `haystack` right after the first occurrence of `needle`.
  Parameters:

  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`

  Returns:
  `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.
  Examples:

      import 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);

size_t `findSkip`(alias pred, R1)(ref R1 `haystack`)
if (isForwardRange!R1 && ifTestable!(typeof(`haystack`.front), unaryFun!pred));
  Advances the `haystack` as long as pred evaluates to true. The `haystack` is positioned so as pred evaluates to `false` for `haystack`.front.
  Parameters:

  R1 `haystack` | The forward range to search in.
  pred | Custom predicate for comparison of `haystack` and needle

  Returns:
  The number of times pred(`haystack`.front) returned `true`.
  Examples:

      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
      import std.stdio;
      s = "  ";
      findSkip!isWhite(s).writeln;

auto `findSplit`(alias pred = "a == b", R1, R2)(R1 `haystack`, R2 `needle`)
if (isForwardRange!R1 && isForwardRange!R2);
auto `findSplitBefore`(alias pred = "a == b", R1, R2)(R1 `haystack`, R2 `needle`)
if (isForwardRange!R1 && isForwardRange!R2);
auto `findSplitAfter`(alias pred = "a == b", R1, R2)(R1 `haystack`, R2 `needle`)
if (isForwardRange!R1 && isForwardRange!R2);
  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.
  Parameters:

  pred | Predicate to use for comparing `needle` against `haystack`.
  R1 `haystack` | The range to search.
  R2 `needle` | What to look for.

  Returns:
  A sub-type of 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 (!result[1].empty) and false otherwise.
  Examples:
  Returning a subtype of std.typecons.Tuple enables the following convenient idiom:

      // findSplit returns a triplet
      if (auto split = "dlang-rocks".findSplit("-"))
          writeln(split[2]); // "rocks"

  Examples:

      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"

  Examples:
  Use std.range.only to find single elements:

      import std.range : only;
      writeln([1, 2, 3, 4].findSplitBefore(only(3))[0]); // [1, 2]

Tuple!(ElementType!Range, size_t) `minCount`(alias pred = "a < b", Range)(Range `range`)
if (isInputRange!Range && !isInfinite!Range && is(typeof(binaryFun!pred(`range`.front, `range`.front))));
Tuple!(ElementType!Range, size_t) `maxCount`(alias pred = "a < b", Range)(Range `range`)
if (isInputRange!Range && !isInfinite!Range && is(typeof(binaryFun!pred(`range`.front, `range`.front))));
  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).
  Parameters:

  pred | The ordering predicate to use to determine the extremum (minimum or maximum).
  Range `range` | The range_primitives.html#.isInputRange">input `range` to count.

  Returns:
  The minimum, respectively maximum element of a `range` together with the number it occurs in the `range`.
  Throws:
  Exception if `range`.empty.
  Examples:

      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)

auto `minElement`(alias map, Range)(Range `r`)
if (isInputRange!Range && !isInfinite!Range);
auto `minElement`(Range)(Range `r`)
if (isInputRange!Range && !isInfinite!Range);
auto `minElement`(alias map, Range, RangeElementType = ElementType!Range)(Range `r`, RangeElementType `seed`)
if (isInputRange!Range && !isInfinite!Range && !is(CommonType!(ElementType!Range, RangeElementType) == void));
auto `minElement`(Range, RangeElementType = ElementType!Range)(Range `r`, RangeElementType `seed`)
if (isInputRange!Range && !isInfinite!Range && !is(CommonType!(ElementType!Range, RangeElementType) == void));
  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.

  Complexity O(n) Exactly n - 1 comparisons are needed.

  Parameters:

  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

  Returns:
  The minimal element of the passed-in range.
  See Also:
  std.algorithm.comparison.min
  Examples:

      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

auto `maxElement`(alias map, Range)(Range `r`)
if (isInputRange!Range && !isInfinite!Range);
auto `maxElement`(Range)(Range `r`)
if (isInputRange!Range && !isInfinite!Range);
auto `maxElement`(alias map, Range, RangeElementType = ElementType!Range)(Range `r`, RangeElementType `seed`)
if (isInputRange!Range && !isInfinite!Range && !is(CommonType!(ElementType!Range, RangeElementType) == void));
auto `maxElement`(Range, RangeElementType = ElementType!Range)(Range `r`, RangeElementType `seed`)
if (isInputRange!Range && !isInfinite!Range && !is(CommonType!(ElementType!Range, RangeElementType) == void));
  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.

  Complexity Exactly n - 1 comparisons are needed.

  Parameters:

  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

  Returns:
  The maximal element of the passed-in range.
  See Also:
  std.algorithm.comparison.max
  Examples:

      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

Range `minPos`(alias pred = "a < b", Range)(Range `range`)
if (isForwardRange!Range && !isInfinite!Range && is(typeof(binaryFun!pred(`range`.front, `range`.front))));
Range `maxPos`(alias pred = "a < b", Range)(Range `range`)
if (isForwardRange!Range && !isInfinite!Range && is(typeof(binaryFun!pred(`range`.front, `range`.front))));
  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).
  Parameters:

  pred | The ordering predicate to use to determine the extremum (minimum or maximum) element.
  Range `range` | The range_primitives.html#.isInputRange">input `range` to search.

  Returns:
  The position of the minimum (respectively maximum) element of forward `range` `range`, i.e. a subrange of `range` starting at the position of its smallest (respectively largest) element and with the same ending as `range`.
  Examples:

      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]

sizediff_t `minIndex`(alias pred = "a < b", Range)(Range `range`)
if (isForwardRange!Range && !isInfinite!Range && is(typeof(binaryFun!pred(`range`.front, `range`.front))));
  Computes the index of the first occurrence of `range`'s minimum element.
  Parameters:

  pred | The ordering predicate to use to determine the minimum element.
  Range `range` | The range_primitives.html#.isInputRange">input `range` to search.

  Complexity O(n) Exactly n - 1 comparisons are needed.

  Returns:
  The index of the first encounter of the minimum element in `range`. If the `range` is empty, -1 is returned.
  See Also:
  std.algorithm.comparison.min, minCount, minElement, minPos
  Examples:

      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

sizediff_t `maxIndex`(alias pred = "a < b", Range)(Range `range`)
if (isInputRange!Range && !isInfinite!Range && is(typeof(binaryFun!pred(`range`.front, `range`.front))));
  Computes the index of the first occurrence of `range`'s maximum element.

  Complexity O(n) Exactly n - 1 comparisons are needed.

  Parameters:

  pred | The ordering predicate to use to determine the maximum element.
  Range `range` | The range_primitives.html#.isInputRange">input `range` to search.

  Returns:
  The index of the first encounter of the maximum in `range`. If the `range` is empty, -1 is returned.
  See Also:
  std.algorithm.comparison.max, maxCount, maxElement, maxPos
  Examples:

      // 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

template `skipOver`(alias pred = "a == b")
  Skip over the initial portion of the first given range that matches the second range, or if no second range is given skip over the elements that fullfil pred. Do nothing if there is no match.
  Parameters:

  pred | The predicate that determines whether elements from each respective range match. Defaults to equality "a == b".

  Examples:

      import std.algorithm.comparison : equal;

      auto s1 = "Hello world";
      assert(!skipOver(s1, "Ha"));
      writeln(s1); // "Hello world"
      assert(skipOver(s1, "Hell") && s1 == "o world");

      string[]  r1 = ["abc", "def", "hij"];
      dstring[] r2 = ["abc"d];
      assert(!skipOver!((a, b) => a.equal(b))(r1, ["def"d]));
      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);

  Examples:

      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'));

  Examples:
  Partial instantiation

      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);

  bool `skipOver`(R1, R2)(ref R1 `r1`, R2 `r2`)
  if (is(typeof(binaryFun!pred(`r1`.front, `r2`.front))) && isForwardRange!R1 && isInputRange!R2);
  bool `skipOver`(R)(ref R `r1`)
  if (isForwardRange!R && ifTestable!(typeof(`r1`.front), unaryFun!pred));
  bool `skipOver`(R, E)(ref R `r`, E `e`)
  if (is(typeof(binaryFun!pred(`r`.front, `e`))) && isInputRange!R);
    `r1` = The forward range to move forward. `r2` = The input range representing the initial segment of `r1` to skip over. `e` = The element to match.
    Returns:
    `true` if the initial segment of `r1` matches `r2` or pred evaluates to `true`, and `r1` has been advanced to the point past this segment; otherwise `false`, and `r1` is left in its original position.
uint `startsWith`(alias pred = "a == b", Range, Needles...)(Range `doesThisStart`, Needles `withOneOfThese`)
if (isInputRange!Range && (Needles.length > 1) && is(typeof(.`startsWith`!pred(`doesThisStart`, `withOneOfThese`[0])) : bool) && is(typeof(.`startsWith`!pred(`doesThisStart`, `withOneOfThese`[1..$])) : uint));
bool `startsWith`(alias pred = "a == b", R1, R2)(R1 `doesThisStart`, R2 `withThis`)
if (isInputRange!R1 && isInputRange!R2 && is(typeof(binaryFun!pred(`doesThisStart`.front, `withThis`.front)) : bool));
bool `startsWith`(alias pred = "a == b", R, E)(R `doesThisStart`, E `withThis`)
if (isInputRange!R && is(typeof(binaryFun!pred(`doesThisStart`.front, `withThis`)) : bool));
bool `startsWith`(alias pred, R)(R `doesThisStart`)
if (isInputRange!R && ifTestable!(typeof(`doesThisStart`.front), unaryFun!pred));
  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.
  Parameters:

  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.

  Returns:
  0 if the needle(s) do not occur at the beginning of the given range; otherwise the position of the matching needle, that is, 1 if the range starts with `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.
  Examples:

      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

alias `OpenRight` = std.typecons.Flag!"openRight".Flag;
  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).
Until!(pred, Range, Sentinel) `until`(alias pred = "a == b", Range, Sentinel)(Range `range`, Sentinel `sentinel`, OpenRight `openRight` = Yes.`openRight`)
if (!is(Sentinel == OpenRight));
Until!(pred, Range, void) `until`(alias pred, Range)(Range `range`, OpenRight `openRight` = Yes.`openRight`);
struct `Until`(alias pred, Range, Sentinel) if (isInputRange!Range);
  Lazily iterates `range` until the element e for which pred(e, `sentinel`) is `true`.
  This is similar to takeWhile in other languages.
  Parameters:

  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`).

  Returns:
  An input range that iterates over the original `range`'s elements, but ends when the specified predicate becomes `true`. If the original `range` is a forward range or higher, this `range` will be a forward `range`.
  Examples:

      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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