std/strings ​

Functions ​

fn Compare(a: str, b: str): int

Returns an integer comparing two strings lexicographically. The result will be 0 if a == b, -1 if a < b, and +1 if a > b.

Use compare when you need to perform a three-way comparison (with [slices::SortFunc], for example). It is usually clearer and always faster to use the built-in string comparison operators ==, <, >, and so on.

fn Count(s: str, substr: str): int

Counts the number of non-overlapping instances of substr in s. If substr is an empty string, returns 1 + the number of Unicode code points in s.

fn Contains(s: str, substr: str): bool

Reports whether substr is within s.

fn ContainsAny(s: str, chars: str): bool

Reports whether any of the UTF-8-encoded code points in chars are within s.

fn ContainsRune(s: str, r: rune): bool

Reports whether the rune is contained in the UTF-8-encoded byte slice s.

fn ContainsFunc(s: str, f: fn(rune): bool): bool

Reports whether any of the UTF-8-encoded code points r within b satisfy f(r).

fn IndexByte(s: str, c: byte): int

Returns the index of the first instance of c in b, or -1 if c is not present in s.

fn LastIndex(s: str, substr: str): int

Returns the index of the last instance of substr in s, or -1 if substr is not present in s.

fn LastIndexByte(s: str, c: byte): int

Returns the index of the last instance of c in s, or -1 if c is not present in s.

fn IndexRune(s: str, r: rune): int

Returns the index of the first instance of the Unicode code point r, or -1 if rune is not present in s. If r is [utf8::RuneError], it returns the first instance of any invalid UTF-8 byte sequence.

fn IndexAny(s: str, chars: str): int

Returns the index of the first instance of any Unicode code point from chars in s, or -1 if no Unicode code point from chars is present in s.

fn LastIndexAny(s: str, chars: str): int

Returns the index of the last instance of any Unicode code point from chars in s, or -1 if no Unicode code point from chars is present in s.

fn SplitN(mut s: str, sep: str, n: int): []str

Slices s into substrings separated by sep and returns a slice of the substrings between those separators.

The count determines the number of substrings to return:

• n > 0: at most n substrings; the last substring will be the unsplit remainder;
• n == 0: the result is nil (zero substrings);
• n < 0: all substrings.

Edge cases for s and sep (for example, empty strings) are handled as described in the documentation for [Split].

To split around the first instance of a separator, see [Cut].

fn SplitAfterN(mut s: str, sep: str, n: int): []str

Slices s into substrings after each instance of sep and returns a slice of those substrings.

The count determines the number of substrings to return:

• n > 0: at most n substrings; the last substring will be the unsplit remainder;
• n == 0: the result is nil (zero substrings);
• n < 0: all substrings.

Edge cases for s and sep (for example, empty strings) are handled as described in the documentation for [SplitAfter].

fn Split(mut s: str, sep: str): []str

Slices s into all substrings separated by sep and returns a slice of the substrings between those separators.

If s does not contain sep and sep is not empty, returns a slice of length 1 whose only element is s.

If sep is empty, splits after each UTF-8 sequence. If both s and sep are empty, returns an empty slice.

It is equivalent to [SplitN] with a count of -1.

To split around the first instance of a separator, see [Cut].

fn SplitAfter(mut s: str, sep: str): []str

Slices s into all substrings after each instance of sep and returns a slice of those substrings.

If s does not contain sep and sep is not empty, returns a slice of length 1 whose only element is s.

If sep is empty, splits after each UTF-8 sequence. If both s and sep are empty, returns an empty slice.

It is equivalent to [SplitAfterN] with a count of -1.

fn Join(elems: []str, sep: str): str

Concatenates the elements of its first argument to create a single string. The separator string sep is placed between elements in the resulting string.

fn HasPrefix(s: str, prefix: str): bool

Reports whether the string s begins with prefix.

fn HasSuffix(s: str, suffix: str): bool

Reports whether the string s ends with suffix.

fn Map(mapping: fn(rune): rune, mut s: str): str

Returns a copy of the string s with all its characters modified according to the mapping function. If mapping returns a negative value, the character is dropped from the string with no replacement.

fn Repeat(s: str, count: int): str

Returns a new string consisting of count copies of the string s.

It panics if count is negative or if the result of (len(s) * count) overflows.

fn IndexFunc(s: str, f: fn(rune): bool): int

Returns the index into s of the first Unicode code point satisfying f(c), or -1 if none do.

fn LastIndexFunc(s: str, f: fn(rune): bool): int

Returns the index into s of the last Unicode code point satisfying f(c), or -1 if none do.

fn TrimLeftFunc(s: str, f: fn(rune): bool): str

Returns a slice of the string s with all leading Unicode code points c satisfying f(c) removed.

fn TrimRight(s: str, cutset: str): str

Returns a slice of the string s, with all trailing Unicode code points contained in cutset removed.

To remove a suffix, use [TrimSuffix] instead.

fn TrimRightFunc(s: str, f: fn(rune): bool): str

Returns a slice of the string s with all trailing Unicode code points c satisfying f(c) removed.

fn TrimFunc(s: str, f: fn(rune): bool): str

Returns a slice of the string s with all leading and trailing Unicode code points c satisfying f(c) removed.

fn TrimPrefix(s: str, prefix: str): str

Returns s without the provided leading prefix string. If s doesn't start with prefix, s is returned unchanged.

fn TrimSuffix(s: str, suffix: str): str

Returns s without the provided trailing suffix string. If s doesn't end with suffix, s is returned unchanged.

fn Trim(s: str, cutset: str): str

Returns a slice of the string s with all leading and trailing Unicode code points contained in cutset removed.

fn TrimLeft(s: str, cutset: str): str

Returns a slice of the string s with all leading Unicode code points contained in cutset removed.

To remove a prefix, use [TrimPrefix] instead.

fn TrimSpace(s: str): str

Returns a slice of the string s, with all leading and trailing white space removed, as defined by Unicode.

fn Replace(s: str, old: str, new: str, mut n: int): str

Returns a copy of the string s with the first n non-overlapping instances of old replaced by new. If old is empty, it matches at the beginning of the string and after each UTF-8 sequence, yielding up to k+1 replacements for a k-rune string. If n < 0, there is no limit on the number of replacements.

fn ReplaceAll(s: str, old: str, new: str): str

Returns a copy of the string s with all non-overlapping instances of old replaced by new. If old is empty, it matches at the beginning of the string and after each UTF-8 sequence, yielding up to k+1 replacements for a k-rune string.

fn EqualFold(mut s: str, mut t: str): bool

Reports whether s and t, interpreted as UTF-8 strings, are equal under simple Unicode case-folding, which is a more general form of case-insensitivity.

fn Index(s: str, substr: str): int

Returns the index of the first instance of substr in s, or -1 if substr is not present in s.

fn Cut(s: str, sep: str): (before: str, after: str, found: bool)

Slices s around the first instance of sep, returning the text before and after sep. The found result reports whether sep appears in s. If sep does not appear in s, returns s, "", false.

fn CutPrefix(s: str, prefix: str): (after: str, found: bool)

Returns s without the provided leading prefix string and reports whether it found the prefix. If s doesn't start with prefix, returns s, false. If prefix is the empty string, returns s, true.

fn CutSuffix(s: str, suffix: str): (before: str, found: bool)

Returns s without the provided ending suffix string and reports whether it found the suffix. If s doesn't end with suffix, returns s, false. If suffix is the empty string, returns s, true.

fn ToUpper(s: str): str

Returns s with all Unicode letters mapped to their upper case.

fn ToLower(s: str): str

Returns s with all Unicode letters mapped to their lower case.

Structs ​

struct Builder

String builder for efficient concatenation. Optimized for single string building not for repeated use.

A Builder must not be copied after first use.

Methods:

fn Write(mut self, b: []byte)!: (n: int)
Writes bytes to buffer. Never throws an exceptional.

fn WriteStr(mut self, s: str)!: (n: int)
Writes bytes to buffer. Never throws an exceptional.

fn WriteByte(mut self, b: byte)!
Writes byte to buffer. Never throws an exceptional.

fn WriteRune(mut self, r: rune)!: (n: int)
Writes rune into buffer. Returns written byte count. Never throws an exceptional.

fn Grow(mut self, n: int)
Grows b's capacity, if necessary, to guarantee space for another n bytes. After Grow(n), at least n bytes can be written to b without another allocation. If n is negative, panics.

fn Str(self): str
Returns buffer as string. Will not reset the underlying content.

fn Clear(mut self)
Clears buffer. After calling this function, write calls will allocate new buffer.

fn Len(self): int
Returns length of buffer.

fn Cap(self): int
Returns capacity of buffer.

unsafe fn Buf(mut self): []byte
Returns mutable buffer for low-level interactions.

unsafe fn SetBuf(mut self, mut buf: []byte)
Sets mutable internal buffer for low-level interactions.