class Sort

Find uses binary search to find and return the smallest index i in [0, n) at which cmp(i) <= 0. If there is no such index i, Find returns i = n. The found result is true if i < n and cmp(i) == 0. Find calls cmp(i) only for i in the range [0, n).

To permit binary search, Find requires that cmp(i) > 0 for a leading prefix of the range, cmp(i) == 0 in the middle, and cmp(i) < 0 for the final suffix of the range. (Each subrange could be empty.) The usual way to establish this condition is to interpret cmp(i) as a comparison of a desired target value t against entry i in an underlying indexed data structure x, returning <0, 0, and >0 when t < x[i], t == x[i], and t > x[i], respectively.

For example, to look for a particular string in a sorted, random-access list of strings:

i, found := sort.Find(x.Len(), func(i int) int {
    return strings.Compare(target, x.At(i))
})
if found {
    fmt.Printf("found %s at entry %d\n", target, i)
} else {
    fmt.Printf("%s not found, would insert at %d", target, i)
}

Float64s sorts a slice of float64s in increasing order. Not-a-number (NaN) values are ordered before other values.

Note: consider using the newer slices.Sort function, which runs faster.

Float64sAreSorted reports whether the slice x is sorted in increasing order, with not-a-number (NaN) values before any other values.

Note: consider using the newer slices.IsSorted function, which runs faster.

Ints sorts a slice of ints in increasing order.

Note: consider using the newer slices.Sort function, which runs faster.

IntsAreSorted reports whether the slice x is sorted in increasing order.

Note: consider using the newer slices.IsSorted function, which runs faster.

IsSorted reports whether data is sorted.

Note: in many situations, the newer slices.IsSortedFunc function is more ergonomic and runs faster.

Reverse returns the reverse order for data.

Search uses binary search to find and return the smallest index i in [0, n) at which f(i) is true, assuming that on the range [0, n), f(i) == true implies f(i+1) == true. That is, Search requires that f is false for some (possibly empty) prefix of the input range [0, n) and then true for the (possibly empty) remainder; Search returns the first true index. If there is no such index, Search returns n. (Note that the "not found" return value is not -1 as in, for instance, strings.Index.) Search calls f(i) only for i in the range [0, n).

A common use of Search is to find the index i for a value x in a sorted, indexable data structure such as an array or slice. In this case, the argument f, typically a closure, captures the value to be searched for, and how the data structure is indexed and ordered.

For instance, given a slice data sorted in ascending order, the call Search(len(data), func(i int) bool { return data[i] >= 23 }) returns the smallest index i such that data[i] >= 23. If the caller wants to find whether 23 is in the slice, it must test data[i] == 23 separately.

Searching data sorted in descending order would use the <= operator instead of the >= operator.

To complete the example above, the following code tries to find the value x in an integer slice data sorted in ascending order:

x := 23
i := sort.Search(len(data), func(i int) bool { return data[i] >= x })
if i < len(data) && data[i] == x {
	// x is present at data[i]
} else {
	// x is not present in data,
	// but i is the index where it would be inserted.
}

As a more whimsical example, this program guesses your number:

func GuessingGame() {
	var s string
	fmt.Printf("Pick an integer from 0 to 100.\n")
	answer := sort.Search(100, func(i int) bool {
		fmt.Printf("Is your number <= %d? ", i)
		fmt.Scanf("%s", &s)
		return s != "" && s[0] == 'y'
	})
	fmt.Printf("Your number is %d.\n", answer)
}

SearchFloat64s searches for x in a sorted slice of float64s and returns the index as specified by Search. The return value is the index to insert x if x is not present (it could be len(a)). The slice must be sorted in ascending order.

SearchInts searches for x in a sorted slice of ints and returns the index as specified by Search. The return value is the index to insert x if x is not present (it could be len(a)). The slice must be sorted in ascending order.

SearchStrings searches for x in a sorted slice of strings and returns the index as specified by Search. The return value is the index to insert x if x is not present (it could be len(a)). The slice must be sorted in ascending order.

Slice sorts the slice x given the provided less function. It panics if x is not a slice.

The sort is not guaranteed to be stable: equal elements may be reversed from their original order. For a stable sort, use SliceStable.

The less function must satisfy the same requirements as the Interface type's Less method.

SliceIsSorted reports whether the slice x is sorted according to the provided less function. It panics if x is not a slice.

SliceStable sorts the slice x using the provided less function, keeping equal elements in their original order. It panics if x is not a slice.

The less function must satisfy the same requirements as the Interface type's Less method.

Sort sorts data in ascending order as determined by the Less method. It makes one call to data.Len to determine n and O(n*log(n)) calls to data.Less and data.Swap. The sort is not guaranteed to be stable.

Note: in many situations, the newer slices.SortFunc function is more ergonomic and runs faster.

Stable sorts data in ascending order as determined by the Less method, while keeping the original order of equal elements.

It makes one call to data.Len to determine n, O(nlog(n)) calls to data.Less and O(nlog(n)*log(n)) calls to data.Swap.

Note: in many situations, the newer slices.SortStableFunc function is more ergonomic and runs faster.

Strings sorts a slice of strings in increasing order.

Note: consider using the newer slices.Sort function, which runs faster.

StringsAreSorted reports whether the slice x is sorted in increasing order.

Note: consider using the newer slices.IsSorted function, which runs faster.