Fast internal iterator.

• since 2.8

The type for strings.

make n c is a string of length n with each index holding the character c.

• raises Invalid_argument

  if n < 0 or n > Sys.max_string_length.

init n ~f is a string of length n with index i holding the character f i (called in increasing index order).

• raises Invalid_argument

  if n < 0 or n > Sys.max_string_length.

• since 4.02

The empty string.

• since 4.13

get s i is the character at index i in s. This is the same as writing s.[i].

• raises Invalid_argument

  if i not an index of s.

Return a new string that contains the same bytes as the given byte sequence.

• since 4.13

Return a new byte sequence that contains the same bytes as the given string.

• since 4.13

concat ~sep ss concatenates the list of strings ss, inserting the separator string sep between each.

• raises Invalid_argument

  if the result is longer than Sys.max_string_length bytes.

cat s1 s2 concatenates s1 and s2 (s1 ^ s2).

• raises Invalid_argument

  if the result is longer than Sys.max_string_length bytes.

• since 4.13

starts_with ~prefix s is true if and only if s starts with prefix.

• since 4.13

ends_with ~suffix s is true if and only if s ends with suffix.

• since 4.13

contains_from s start c is true if and only if c appears in s after position start.

• raises Invalid_argument

  if start is not a valid position in s.

rcontains_from s stop c is true if and only if c appears in s before position stop+1.

• raises Invalid_argument

  if stop < 0 or stop+1 is not a valid position in s.

contains s c is String.contains_from s 0 c.

sub s ~pos ~len is a string of length len, containing the substring of s that starts at position pos and has length len.

• raises Invalid_argument

  if pos and len do not designate a valid substring of s.

map f s is the string resulting from applying f to all the characters of s in increasing order.

• since 4.00

mapi ~f s is like map but the index of the character is also passed to f.

• since 4.02

fold_left f x s computes f (... (f (f x s.[0]) s.[1]) ...) s.[n-1], where n is the length of the string s.

• since 4.13

fold_right f s x computes f s.[0] (f s.[1] ( ... (f s.[n-1] x) ...)), where n is the length of the string s.

• since 4.13

trim s is s without leading and trailing whitespace. Whitespace characters are: ' ', '\x0C' (form feed), '\n', '\r', and '\t'.

• since 4.00

escaped s is s with special characters represented by escape sequences, following the lexical conventions of OCaml.

All characters outside the US-ASCII printable range [0x20;0x7E] are escaped, as well as backslash (0x2F) and double-quote (0x22).

The function Scanf.unescaped is a left inverse of escaped, i.e. Scanf.unescaped (escaped s) = s for any string s (unless escaped s fails).

• raises Invalid_argument

  if the result is longer than Sys.max_string_length bytes.

iteri is like iter, but the function is also given the corresponding character index.

• since 4.00

index_from s i c is the index of the first occurrence of c in s after position i.

• raises Not_found

  if c does not occur in s after position i.

• raises Invalid_argument

  if i is not a valid position in s.

index_from_opt s i c is the index of the first occurrence of c in s after position i (if any).

• raises Invalid_argument

  if i is not a valid position in s.

• since 4.05

rindex_from s i c is the index of the last occurrence of c in s before position i+1.

• raises Not_found

  if c does not occur in s before position i+1.

• raises Invalid_argument

  if i+1 is not a valid position in s.

rindex_from_opt s i c is the index of the last occurrence of c in s before position i+1 (if any).

• raises Invalid_argument

  if i+1 is not a valid position in s.

• since 4.05

index s c is String.index_from s 0 c.

index_opt s c is String.index_from_opt s 0 c.

• since 4.05

rindex s c is String.rindex_from s (length s - 1) c.

rindex_opt s c is String.rindex_from_opt s (length s - 1) c.

• since 4.05

to_seqi s is like to_seq but also tuples the corresponding index.

• since 4.07

get_utf_8_uchar b i decodes an UTF-8 character at index i in b.

is_valid_utf_8 b is true if and only if b contains valid UTF-8 data.

get_utf_16be_uchar b i decodes an UTF-16BE character at index i in b.

is_valid_utf_16be b is true if and only if b contains valid UTF-16BE data.

get_utf_16le_uchar b i decodes an UTF-16LE character at index i in b.

is_valid_utf_16le b is true if and only if b contains valid UTF-16LE data.

get_uint8 b i is b's unsigned 8-bit integer starting at character index i.

• since 4.13

get_int8 b i is b's signed 8-bit integer starting at character index i.

• since 4.13

get_uint16_ne b i is b's native-endian unsigned 16-bit integer starting at character index i.

• since 4.13

get_uint16_be b i is b's big-endian unsigned 16-bit integer starting at character index i.

• since 4.13

get_uint16_le b i is b's little-endian unsigned 16-bit integer starting at character index i.

• since 4.13

get_int16_ne b i is b's native-endian signed 16-bit integer starting at character index i.

• since 4.13

get_int16_be b i is b's big-endian signed 16-bit integer starting at character index i.

• since 4.13

get_int16_le b i is b's little-endian signed 16-bit integer starting at character index i.

• since 4.13

get_int32_ne b i is b's native-endian 32-bit integer starting at character index i.

• since 4.13

A seeded hash function for strings, with the same output value as Hashtbl.seeded_hash. This function allows this module to be passed as argument to the functor Hashtbl.MakeSeeded.

• since 5.0

get_int32_be b i is b's big-endian 32-bit integer starting at character index i.

• since 4.13

get_int32_le b i is b's little-endian 32-bit integer starting at character index i.

• since 4.13

get_int64_ne b i is b's native-endian 64-bit integer starting at character index i.

• since 4.13

get_int64_be b i is b's big-endian 64-bit integer starting at character index i.

• since 4.13

get_int64_le b i is b's little-endian 64-bit integer starting at character index i.

• since 4.13

length s returns the length (number of characters) of the given string s.

blit ~src ~src_pos ~dst ~dst_pos ~len copies len characters from string src starting at character indice src_pos, to the Bytes sequence dst starting at character indice dst_pos. Like String.blit. Compatible with the -safe-string option.

• raises Invalid_argument

  if indices are not valid.

fold ~f ~init s folds on chars by increasing index. Computes f(… (f (f init s.[0]) s.[1]) …) s.[n-1].

• since 0.7

foldi ~f init s is just like fold, but it also passes in the index of each chars as second argument to the folded function f.

• since 3.3

to_gen s returns the gen of characters contained in the string s.

to_iter s returns the iter of characters contained in the string s.

• since 2.8

to_seq s returns the Seq.t of characters contained in the string s. Renamed from to std_seq since 3.0.

• since 3.0

to_list s returns the list of characters contained in the string s.

pp_buf buf s prints s to the buffer buf. Renamed from pp since 2.0.

pp f s prints the string s within quotes to the formatter f. Renamed from print since 2.0.

equal s1 s2 returns true iff the strings s1 and s2 are equal.

compare s1 s2 compares the strings s1 and s2 and returns an integer that indicates their relative position in the sort order.

is_empty s returns true iff s is empty (i.e. its length is 0).

• since 1.5

hash s returns the hash value of s.

rev s returns the reverse of s.

• since 0.17

pad ?side ?c n s ensures that the string s is at least n bytes long, and pads it on the side with c if it's not the case.

• parameter side

  determines where padding occurs (default: `Left).

• parameter c

  the char used to pad (default: ' ').

• since 0.17

of_char 'a' is "a".

• since 0.19

of_gen gen converts a gen of characters to a string.

of_iter iter converts an iter of characters to a string.

• since 2.8

of_seq seq converts a seq of characters to a string. Renamed from of_std_seq since 3.0.

• since 3.0

of_list lc converts a list of characters lc to a string.

of_array ac converts an array of characters ac to a string.

to_array s returns the array of characters contained in the string s.

find ?start ~sub s returns the starting index of the first occurrence of sub within s or -1.

• parameter start

  starting position in s.

find_all ?start ~sub s finds all occurrences of sub in s, even overlapping instances and returns them in a generator gen.

• parameter start

  starting position in s.

• since 0.17

find_all_l ?start ~sub s finds all occurrences of sub in s and returns them in a list.

• parameter start

  starting position in s.

• since 0.17

mem ?start ~sub s is true iff sub is a substring of s.

• since 0.12

rfind ~sub s finds sub in string s from the right, returns its first index or -1. Should only be used with very small sub.

• since 0.12

replace ?which ~sub ~by s replaces some occurrences of sub by by in s.

• parameter which

  decides whether the occurrences to replace are:

  • `Left first occurrence from the left (beginning).
  • `Right first occurrence from the right (end).
  • `All all occurrences (default).

• raises Invalid_argument

  if sub = "".

• since 0.14

is_sub ~sub ~sub_pos s ~pos ~sub_len returns true iff the substring of sub starting at position sub_pos and of length sub_len is a substring of s starting at position pos.

repeat s n creates a string by repeating the string s n times.

prefix ~pre s returns true iff pre is a prefix of s.

suffix ~suf s returns true iff suf is a suffix of s.

• since 0.7

chop_prefix ~pre s removes pre from s if pre really is a prefix of s, returns None otherwise.

• since 0.17

chop_suffix ~suf s removes suf from s if suf really is a suffix of s, returns None otherwise.

• since 0.17

take n s keeps only the n first chars of s.

• since 0.17

take_while ~f s keeps only the longest prefix t of s such that every character c in t satisfies f c.

• since 3.16

rtake_while ~f s keeps only the longest suffix t of s such that every character c in t satisfies f c.

• since 3.16

drop n s removes the n first chars of s.

• since 0.17

take_drop n s is take n s, drop n s.

• since 0.17

lines s returns a list of the lines of s (splits along '\n').

• since 0.10

lines_gen s returns a generator gen of the lines of s (splits along '\n').

• since 0.10

lines_iter s returns the iter of the lines of s (splits along '\n').

• since 3.2

lines_seq s returns the Seq.t of the lines of s (splits along '\n').

• since 3.2

concat_iter ~sep iter concatenates all strings of iter, separated with sep.

• since 3.2

concat_gen ~sep gen concatenates all strings of gen, separated with sep.

• since 0.10

concat_seq ~sep seq concatenates all strings of seq, separated with sep.

• since 3.2

unlines ls concatenates all strings of ls, separated with '\n'.

• since 0.10

unlines_gen gen concatenates all strings of gen, separated with '\n'.

• since 0.10

unlines_iter iter concatenates all strings of iter, separated with '\n'.

• since 3.2

unlines_seq seq concatenates all strings of seq, separated with '\n'.

• since 3.2

set s i c creates a new string which is a copy of s, except for index i, which becomes c.

• raises Invalid_argument

  if i is an invalid index.

• since 0.12

iter ~f s applies function f on each character of s. Alias to String.iter.

• since 0.12

filter_map ~f s calls (f a0) (f a1) … (f an) where a0 … an are the characters of s. It returns the string of characters ci such as f ai = Some ci (when f returns None, the corresponding element of s is discarded).

• since 0.17

filter ~f s discards characters of s not satisfying f.

• since 0.17

uniq ~eq s remove consecutive duplicate characters in s.

• since 3.4

flat_map ?sep ~f s maps each chars of s to a string, then concatenates them all.

• parameter sep

  optional separator between each generated string.

• since 0.12

for_all ~f s is true iff all characters of s satisfy the predicate f.

• since 0.12

exists ~f s is true iff some character of s satisfy the predicate f.

• since 0.12

drop_while ~f s discards any characters of s starting from the left, up to the first character c not satisfying f c.

• since 2.2

rdrop_while ~f s discards any characters of s starting from the right, up to the first character c not satisfying f c.

• since 2.2

ltrim s trims space on the left (see String.trim for more details).

• since 1.2

rtrim s trims space on the right (see String.trim for more details).

• since 1.2

map2 ~f s1 s2 maps pairs of chars.

• raises Invalid_argument

  if the strings have not the same length.

• since 0.12

iter2 ~f s1 s2 iterates on pairs of chars.

• raises Invalid_argument

  if the strings have not the same length.

• since 0.12

iteri2 ~f s1 s2 iterates on pairs of chars with their index.

• raises Invalid_argument

  if the strings have not the same length.

• since 0.12

fold2 ~f ~init s1 s2 folds on pairs of chars.

• raises Invalid_argument

  if the strings have not the same length.

• since 0.12

for_all2 ~f s1 s2 returns true iff all pairs of chars satisfy the predicate f.

• raises Invalid_argument

  if the strings have not the same length.

• since 0.12

exists2 ~f s1 s2 returns true iff a pair of chars satisfy the predicate f.

• raises Invalid_argument

  if the strings have not the same length.

• since 0.12

capitalize_ascii s returns a copy of s with the first character set to uppercase using the US-ASCII character set. See String.

• since 0.18

uncapitalize_ascii s returns a copy of s with the first character set to lowercase using the US-ASCII character set. See String.

• since 0.18

uppercase_ascii s returns a copy of s with all lowercase letters translated to uppercase using the US-ASCII character set. See String.

• since 0.18

lowercase_ascii s returns a copy of s with all uppercase letters translated to lowercase using the US-ASCII character set. See String.

• since 0.18

equal_caseless s1 s2 compares s1 and s2 without respect to ascii lowercase.

• since 1.2

Convert a string with arbitrary content into a hexadecimal string.

• since 3.8

Convert a string in hex into a string with arbitrary content.

• since 3.8

Same as of_hex but fails harder.

• raises Invalid_argument

  if the input is not valid hex.

• since 3.8

split_on_char ~by s splits the string s along the given char by.

• since 1.2

split ~by s splits the string s along the given string by. Alias to Split.list_cpy.

• since 1.2

compare_versions s1 s2 compares version strings s1 and s2, considering that numbers are above text.

• since 0.13

compare_natural s1 s2 is the Natural Sort Order, comparing chunks of digits as natural numbers. https://en.wikipedia.org/wiki/Natural_sort_order

• since 1.3

edit_distance ?cutoff s1 s2 is the edition distance between the two strings s1 and s2. This satisfies the classical distance axioms: it is always positive, symmetric, and satisfies the formula distance s1 s2 + distance s2 s3 >= distance s1 s3.

• parameter cutoff

  if provided, it's a cap on both the number of iterations, and on the result. (since 3.0). This is useful if you just want to check whether the edit distance is less or equal than 2 (use cutoff of 3).