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Module `std.algorithm.comparison`

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

Cheat Sheet
Function Name	Description
`among`	Checks if a value is among a set of values, e.g. `if (v.among(1, 2, 3)) //` v `is 1, 2 or 3`
`castSwitch`	`(new A()).castSwitch((A a)=>1,(B b)=>2)` returns `1`.
`clamp`	`clamp(1, 3, 6)` returns `3`. `clamp(4, 3, 6)` returns `4`.
`cmp`	`cmp("abc", "abcd")` is `-1`, `cmp("abc", "aba")` is `1`, and `cmp("abc", "abc")` is `0`.
`either`	Return first parameter `p` that passes an `if (p)` test, e.g. `either(0, 42, 43)` returns `42`.
`equal`	Compares ranges for element-by-element equality, e.g. `equal([1, 2, 3], [1.0, 2.0, 3.0])` returns `true`.
`isPermutation`	`isPermutation([1, 2], [2, 1])` returns `true`.
`isSameLength`	`isSameLength([1, 2, 3], [4, 5, 6])` 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")`.
`predSwitch`	`2.predSwitch(1, "one", 2, "two", 3, "three")` returns `"two"`.

Functions

Name	Description
`among(value, values)`	Find `value` among `values`, returning the 1-based index of the first matching value in `values`, or `0` if `value` is not among `values`. The predicate `pred` is used to compare values, and uses equality by default.
`castSwitch(switchObject)`	Executes and returns one of a collection of handlers based on the type of the switch object.
`clamp(val, lower, upper)`	Clamps a value into the given bounds.
`cmp(r1, r2)`	Performs a lexicographical comparison on two input ranges. Iterating `r1` and `r2` in lockstep, `cmp` compares each element `e1` of `r1` with the corresponding element `e2` in `r2`. 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.
`either(first, alternatives)`	Get the first argument `a` that passes an `if (unaryFun!pred(a))` test. If no argument passes the test, return the last argument.
`isPermutation(r1, r2)`	Checks if both ranges are permutations of each other.
`isSameLength(r1, r2)`	Checks if the two ranges have the same number of elements. This function is optimized to always take advantage of the `length` member of either range if it exists.
`levenshteinDistance(s, t)`	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(`min(s.length, t.length)`) storage.
`levenshteinDistanceAndPath(s, t)`	Returns the Levenshtein distance and the edit path between `s` and `t`.
`max(args)`	Iterates the passed arguments and returns the maximum value.
`min(args)`	Iterates the passed arguments and returns the minimum value.
`mismatch(r1, r2)`	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`.
`predSwitch(switchExpression, choices)`	Returns one of a collection of expressions based on the value of the switch expression.

Enums

Name Description

EditOp 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.

Name	Description
`EditOp`	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.

Templates

Name	Description
`among`	Find `value` among `values`, returning the 1-based index of the first matching value in `values`, or `0` if `value` is not among `values`. The predicate `pred` is used to compare values, and uses equality by default.
`equal`	Compares two ranges for equality, as defined by predicate `pred` (which is `==` by default).

Authors

Andrei Alexandrescu

License

Boost License 1.0.