Module Stdlib.String

Strings
Concatenating
Predicates and comparisons
Extracting substrings
Transforming
Traversing
Searching
Strings and Sequences
UTF decoding and validations
- UTF-8
- UTF-16BE
- UTF-16LE
Deprecated functions
Binary decoding of integers

Instructions: Use this module in your project

In the IDE (CLion, Visual Studio Code, Xcode, etc.) you use for your DkSDK project:

Add the following to your project's dependencies/CMakeLists.txt:

Copy

DkSDKProject_DeclareAvailable(ocaml
    CONSTRAINT "= 4.14.0"
    FINDLIBS str unix runtime_events threads dynlink)
DkSDKProject_MakeAvailable(ocaml)

Add the Findlib::ocaml library to any desired targets in src/*/CMakeLists.txt:

Copy

target_link_libraries(YourPackage_YourLibraryName
     # ... existing libraries, if any ...
     Findlib::ocaml)

Click your IDE's Build button

Not using DkSDK?

FIRST, do one or all of the following:

Run:
Copy
```
opam install ocaml.4.14.0
```

Edit your dune-project and add:

Copy

(package
  (name YourExistingPackage)
  (depends
  ; ... existing dependenices ...
  (ocaml (>= 4.14.0))))

Then run:

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dune build *.opam # if this fails, run: dune build

Edit your <package>.opam file and add:

Copy

depends: [
  # ... existing dependencies ...
  "ocaml" {>= "4.14.0"}
]

Then run:

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opam install . --deps-only

FINALLY, add the library to any desired (library)and/or (executable) targets in your **/dune files:

Copy

(library
  (name YourLibrary)
  ; ... existing library options ...
  (libraries
    ; ... existing libraries ...
    ))

(executable
  (name YourExecutable)
  ; ... existing executable options ...
  (libraries
    ; ... existing libraries ...
    ))

Strings

type t`` = string

The type for strings.

valmake : ``int->``char-> string

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.

valinit : ``int->``(``int->char)``-> string

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 4.02.0

val empty : string

The empty string.

since 4.13.0

valof_bytes : ``bytes-> string

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

since 4.13.0

valto_bytes : ``string-> bytes

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

since 4.13.0

vallength : ``string-> int

length s is the length (number of bytes/characters) of s.

valget : ``string->``int-> char

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.

Concatenating

Note. The Stdlib.(^) binary operator concatenates two strings.

valconcat : ``string->``string list``-> string

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.

valcat : ``string->``string-> string

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

raises Invalid_argument

if the result is longer then than Sys.max_string_length bytes.
since 4.13.0

Predicates and comparisons

valequal :t -> t -> bool

equal s0 s1 is true if and only if s0 and s1 are character-wise equal.

since 4.03.0 (4.05.0 in StringLabels)

valcompare :t -> t -> int

compare s0 s1 sorts s0 and s1 in lexicographical order. compare behaves like Stdlib.compare on strings but may be more efficient.

valstarts_with : ``prefix:string->``string-> bool

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

since 4.13.0

valends_with : ``suffix:string->``string-> bool

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

since 4.13.0

valcontains_from : ``string->``int->``char-> bool

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.

valrcontains_from : ``string->``int->``char-> bool

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.

valcontains : ``string->``char-> bool

contains s c is String.contains_from s 0 c.

Extracting substrings

valsub : ``string->``int->``int-> string

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.

valsplit_on_char : ``char->``string-> ``string list

split_on_char sep s is the list of all (possibly empty) substrings of s that are delimited by the character sep.

The function's result is specified by the following invariants:

The list is not empty.
Concatenating its elements using sep as a separator returns a string equal to the input (concat (make 1 sep) (split_on_char sep s) = s).
No string in the result contains the sep character.
since 4.04.0 (4.05.0 in StringLabels)

Transforming

valmap : ``(``char->char)``->``string-> string

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

since 4.00.0

valmapi : ``(``int->``char->char)``->``string-> string

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

since 4.02.0

val fold_left : ``('a ->``char-> 'a)`` -> 'a ->``string-> 'a

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 4.13.0

valfold_right : ``(``char-> 'a -> 'a)`` ->``string-> 'a -> 'a

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 4.13.0

valfor_all : ``(``char->bool)``->``string-> bool

for_all p s checks if all characters in s satisfy the predicate p.

since 4.13.0

valexists : ``(``char->bool)``->``string-> bool

exists p s checks if at least one character of s satisfies the predicate p.

since 4.13.0

valtrim : ``string-> string

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

since 4.00.0

valescaped : ``string-> string

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.

valuppercase_ascii : ``string-> string

uppercase_ascii s is s with all lowercase letters translated to uppercase, using the US-ASCII character set.

since 4.03.0 (4.05.0 in StringLabels)

vallowercase_ascii : ``string-> string

lowercase_ascii s is s with all uppercase letters translated to lowercase, using the US-ASCII character set.

since 4.03.0 (4.05.0 in StringLabels)

valcapitalize_ascii : ``string-> string

capitalize_ascii s is s with the first character set to uppercase, using the US-ASCII character set.

since 4.03.0 (4.05.0 in StringLabels)

valuncapitalize_ascii : ``string-> string

uncapitalize_ascii s is s with the first character set to lowercase, using the US-ASCII character set.

since 4.03.0 (4.05.0 in StringLabels)

Traversing

valiter : ``(``char->unit)``->``string-> unit

iter f s applies function f in turn to all the characters of s. It is equivalent to f s.[0]; f s.[1]; ...; f s.[length s - 1]; ().

valiteri : ``(``int->``char->unit)``->``string-> unit

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

since 4.00.0

Searching

valindex_from : ``string->``int->``char-> int

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.

valindex_from_opt : ``string->``int->``char-> ``int option

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

valrindex_from : ``string->``int->``char-> int

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.

valrindex_from_opt : ``string->``int->``char-> ``int option

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

valindex : ``string->``char-> int

index s c is String.index_from s 0 c.

valindex_opt : ``string->``char-> ``int option

index_opt s c is String.index_from_opt s 0 c.

since 4.05

valrindex : ``string->``char-> int

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

valrindex_opt : ``string->``char-> ``int option

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

since 4.05

Strings and Sequences

valto_seq :t ->``charSeq.t

to_seq s is a sequence made of the string's characters in increasing order. In "unsafe-string" mode, modifications of the string during iteration will be reflected in the sequence.

since 4.07

valto_seqi :t ->``(int * char)``Seq.t

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

since 4.07

valof_seq : ``charSeq.t -> t

of_seq s is a string made of the sequence's characters.

since 4.07

UTF decoding and validations

since 4.14

UTF-8

valget_utf_8_uchar :t ->``int-> Uchar.utf_decode

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

valis_valid_utf_8 :t -> bool

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

UTF-16BE

valget_utf_16be_uchar :t ->``int-> Uchar.utf_decode

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

valis_valid_utf_16be :t -> bool

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

UTF-16LE

valget_utf_16le_uchar :t ->``int-> Uchar.utf_decode

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

valis_valid_utf_16le :t -> bool

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

Deprecated functions

valcreate : ``int-> bytes

create n returns a fresh byte sequence of length n. The sequence is uninitialized and contains arbitrary bytes.

raises Invalid_argument

if n < 0 or n > Sys.max_string_length.
deprecated

This is a deprecated alias of Bytes.create/BytesLabels.create.

valset : ``bytes->``int->``char-> unit

set s n c modifies byte sequence s in place, replacing the byte at index n with c. You can also write s.[n] <- c instead of set s n c.

raises Invalid_argument

if n is not a valid index in s.
deprecated

This is a deprecated alias of Bytes.set/BytesLabels.set.

valblit : ``string->``int->``bytes->``int->``int-> unit

blit src src_pos dst dst_pos len copies len bytes from the string src, starting at index src_pos, to byte sequence dst, starting at character number dst_pos.

raises Invalid_argument

if src_pos and len do not designate a valid range of src, or if dst_pos and len do not designate a valid range of dst.

valcopy : ``string-> string

Return a copy of the given string.

deprecated

Because strings are immutable, it doesn't make much sense to make identical copies of them.

valfill : ``bytes->``int->``int->``char-> unit

fill s pos len c modifies byte sequence s in place, replacing len bytes by c, starting at pos.

raises Invalid_argument

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

This is a deprecated alias of Bytes.fill/BytesLabels.fill.

valuppercase : ``string-> string

Return a copy of the argument, with all lowercase letters translated to uppercase, including accented letters of the ISO Latin-1 (8859-1) character set.

deprecated

Functions operating on Latin-1 character set are deprecated.

vallowercase : ``string-> string

Return a copy of the argument, with all uppercase letters translated to lowercase, including accented letters of the ISO Latin-1 (8859-1) character set.

deprecated

Functions operating on Latin-1 character set are deprecated.

valcapitalize : ``string-> string

Return a copy of the argument, with the first character set to uppercase, using the ISO Latin-1 (8859-1) character set..

deprecated

Functions operating on Latin-1 character set are deprecated.

valuncapitalize : ``string-> string

Return a copy of the argument, with the first character set to lowercase, using the ISO Latin-1 (8859-1) character set.

deprecated

Functions operating on Latin-1 character set are deprecated.

Binary decoding of integers

The functions in this section binary decode integers from strings.

All following functions raise Invalid_argument if the characters needed at index i to decode the integer are not available.

Little-endian (resp. big-endian) encoding means that least (resp. most) significant bytes are stored first. Big-endian is also known as network byte order. Native-endian encoding is either little-endian or big-endian depending on Sys.big_endian.

32-bit and 64-bit integers are represented by the int32 and int64 types, which can be interpreted either as signed or unsigned numbers.

8-bit and 16-bit integers are represented by the int type, which has more bits than the binary encoding. These extra bits are sign-extended (or zero-extended) for functions which decode 8-bit or 16-bit integers and represented them with int values.

valget_uint8 : ``string->``int-> int

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

since 4.13.0

valget_int8 : ``string->``int-> int

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

since 4.13.0

valget_uint16_ne : ``string->``int-> int

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

since 4.13.0

valget_uint16_be : ``string->``int-> int

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

since 4.13.0

valget_uint16_le : ``string->``int-> int

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

since 4.13.0

valget_int16_ne : ``string->``int-> int

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

since 4.13.0

valget_int16_be : ``string->``int-> int

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

since 4.13.0

valget_int16_le : ``string->``int-> int

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

since 4.13.0

valget_int32_ne : ``string->``int-> int32

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

since 4.13.0

valget_int32_be : ``string->``int-> int32

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

since 4.13.0

valget_int32_le : ``string->``int-> int32

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

since 4.13.0

valget_int64_ne : ``string->``int-> int64

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

since 4.13.0

valget_int64_be : ``string->``int-> int64

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

since 4.13.0

valget_int64_le : ``string->``int-> int64

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

since 4.13.0

</stdlib.html#val-(%5e)>

More from the DkSDK Book

1. DkSDK
1. 1. Package capnp
  1. 1. Module Capnp
    1. 1. Module type MessageSig.MESSAGE
        Module type MessageSig.S
        Module S.ListStorage
        Module S.Message
        Module S.Object
        Module S.Segment
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        Module type MessageSig.SEGMENT
        Module type MessageSig.SLICE
    1. Module Capnp_unix
  1. Package cmdliner
  1. 1. Module Cmdliner
    1. Module Cmdliner_arg
    1. Module Cmdliner_base
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    1. Module Cmdliner_cmd
    1. Module Cmdliner_docgen
    1. Module Cmdliner_eval
    1. Module Cmdliner_info
    1. Module Cmdliner_manpage
    1. Module Cmdliner_msg
    1. Module Cmdliner_term
    1. Module Cmdliner_term_deprecated
    1. Module Cmdliner_trie
  1. Package fmt
  1. 1. Module Fmt
    1. Module Fmt_cli
    1. Module Fmt_tty
  1. Package logs
  1. 1. Module Logs
    1. 1. Module type Logs.LOG
      1. ...
    1. Module Logs_cli
    1. Module Logs_fmt
    1. Module Logs_lwt
    1. 1. Module type Logs_lwt.LOG
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  1. Package lwt
  1. 1. Module Lwt
    1. Module Lwt_bytes
    1. Module Lwt_condition
    1. Module Lwt_config
    1. Module Lwt_engine
    1. Module Lwt_features
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    1. Module Lwt_gc
    1. Module Lwt_io
    1. 1. Module type Lwt_io.NumberIO
    1. Module Lwt_list
    1. Module Lwt_main
    1. 1. Module type Lwt_main.Hooks
    1. Module Lwt_mutex
    1. Module Lwt_mvar
    1. Module Lwt_pool
    1. Module Lwt_pqueue
    1. 1. Module type Lwt_pqueue.OrderedType
        Module type Lwt_pqueue.S
    1. Module Lwt_preemptive
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  1. Package ocaml
  1. 1. Module Bigarray
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