stdlib_strings.md

title
strings

The stdlib_strings module

[TOC]

Introduction

The stdlib_strings module provides basic string handling and manipulation routines.

Procedures and methods provided

strip

Description

Remove leading and trailing whitespace characters.

Syntax

string = [[stdlib_strings(module):strip(interface)]] (string)

Status

Experimental

Class

Pure function.

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).

Result value

The result is of the same type as string.

Example

{!example/strings/example_strip.f90!}

chomp

Description

Remove trailing characters in set or substring from string. If no character set or substring is provided trailing whitespace is removed.

Syntax

string = [[stdlib_strings(module):chomp(interface)]] (string[, set|substring])

Status

Experimental

Class

Pure function.

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• set: Array of length one character. This argument is intent(in).
• substring: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).

Result value

The result is of the same type as string.

Example

{!example/strings/example_chomp.f90!}

starts_with

Description

Check if a string starts with a given substring.

Syntax

string = [[stdlib_strings(module):starts_with(interface)]] (string, substring)

Status

Experimental

Class

Pure function.

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• substring: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).

Result value

The result is of scalar logical type.

Example

{!example/strings/example_starts_with.f90!}

ends_with

Description

Check if a string ends with a given substring.

Syntax

string = [[stdlib_strings(module):ends_with(interface)]] (string, substring)

Status

Experimental

Class

Pure function.

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• substring: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).

Result value

The result is of scalar logical type.

Example

{!example/strings/example_ends_with.f90!}

slice

Description

Extracts the characters from the defined region of the input string by taking strides.
Argument first and last defines this region for extraction by function slice.
Argument stride defines the magnitude and direction (+/-) of stride to be taken while extraction. stride when given invalid value 0, is converted to +1.

Deduction Process:
Function first automatically deduces the optional arguments that are not provided by the user.
Deduced first and last argument take +infinity or -infinity value and deduced stride argument takes value +1 or -1 depending upon the actual argument(s) provided by the user.

Extraction Process:
Extraction starts only if last is crossable from first with stride of stride.
Extraction starts from the first valid index in the defined region to take stride of stride and ends when the last valid index in the defined region is crossed.
If no valid index exists in the defined region, empty string is returned.

Syntax

string = [[stdlib_strings(module):slice(interface)]] (string [, first, last, stride])

Status

Experimental

Class

Pure function.

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• first: integer. This argument is intent(in) and optional.
• last: integer. This argument is intent(in) and optional.
• stride: integer. This argument is intent(in) and optional.

Result value

The result is of the same type as string.

Example

{!example/strings/example_slice.f90!}

find

Description

Returns the starting index of the occurrenceth occurrence of the substring pattern in the input string string.
Default value of occurrence is set to 1. If consider_overlapping is not provided or is set to .true. the function counts two overlapping occurrences of substring pattern as two different occurrences.
If occurrenceth occurrence is not found, function returns 0.

Syntax

string = [[stdlib_strings(module):find(interface)]] (string, pattern [, occurrence, consider_overlapping])

Status

Experimental

Class

Elemental function

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• pattern: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• occurrence: integer. This argument is intent(in) and optional.
• consider_overlapping: logical. This argument is intent(in) and optional.

Result value

The result is a scalar of integer type or an integer array of rank equal to the highest rank among all dummy arguments.

Example

{!example/strings/example_find.f90!}

replace_all

Description

Replaces all occurrences of substring pattern in the input string with the replacement replacement.
Occurrences overlapping on a base occurrence will not be replaced.

Syntax

string = [[stdlib_strings(module):replace_all(interface)]] (string, pattern, replacement)

Status

Experimental

Class

Pure function

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• pattern: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• replacement: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).

Result value

The result is of the same type as string.

Example

{!example/strings/example_replace_all.f90!}

padl

Description

Returns a string of length output_length left padded with pad_with character if it is provided, otherwise with " " (1 whitespace).
If output_length is less than or equal to the length of string, padding is not performed.

Syntax

string = [[stdlib_strings(module):padl(interface)]] (string, output_length [, pad_with])

Status

Experimental

Class

Pure function

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• output_length: integer. This argument is intent(in).
• pad_with: Character scalar of length 1. This argument is intent(in) and optional.

Result value

The result is of the same type as string.

Example

{!example/strings/example_padl.f90!}

padr

Description

Returns a string of length output_length right padded with pad_with character if it is provided, otherwise with " " (1 whitespace).
If output_length is less than or equal to the length of string, padding is not performed.

Syntax

string = [[stdlib_strings(module):padr(interface)]] (string, output_length [, pad_with])

Status

Experimental

Class

Pure function

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• output_length: integer. This argument is intent(in).
• pad_with: Character scalar of length 1. This argument is intent(in) and optional.

Result value

The result is of the same type as string.

Example

{!example/strings/example_padr.f90!}

count

Description

Returns the number of times the substring pattern has occurred in the input string string.
If consider_overlapping is not provided or is set to .true. the function counts two overlapping occurrences of substring pattern as two different occurrences.

Syntax

string = [[stdlib_strings(module):count(interface)]] (string, pattern [, consider_overlapping])

Status

Experimental

Class

Elemental function

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• pattern: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• consider_overlapping: logical. This argument is intent(in) and optional.

Result value

The result is a scalar of integer type or an integer array of rank equal to the highest rank among all dummy arguments.

Example

{!example/strings/example_count.f90!}

zfill

Description

Returns a string of length output_length left-padded with zeros. If output_length is less than or equal to the length of string, padding is not performed.

Syntax

string = [[stdlib_strings(module):zfill(interface)]] (string, output_length)

Status

Experimental

Class

Pure function

Argument

• string: Character scalar or [[stdlib_string_type(module):string_type(type)]]. This argument is intent(in).
• output_length: integer. This argument is intent(in).

Result value

The result is of the same type as string.

Example

{!example/strings/example_zfill.f90!}

join

Description

Joins an array of strings into a single string. This function concatenates the strings from the input array, inserting a separator between each string (default: space). A user-defined separator may be provided, The resulting string is returned.

Syntax

joined = [[stdlib_strings(module):join(interface)]] (strings, separator)

Status

Experimental

Class

Pure function

Argument

• strings: Array of strings (either type(string_type) or character(len=*)). This argument is intent(in). It is an array of strings that will be concatenated together.
• separator: character(len=*) scalar (optional). This argument is intent(in). It specifies the separator to be used between the strings. If not provided, the default separator (a space) is used.

Result value

The result is of the same type as the elements of strings (type(string_type) or character(len=:), allocatable).

Example

{!example/strings/example_join.f90!}

to_string

Description

Format or transfer a integer/real/complex/logical scalar as a string.
Input a wrong format that cause the internal-IO to fail, the result value is a string of [*].

Syntax

string = [[stdlib_strings(module):to_string(interface)]] (value [, format])

Status

Experimental

Class

Pure function.

Argument

• value: Shall be an integer/real/complex/logical scalar. This is an intent(in) argument.
• format: Shall be a character(len=*) scalar like '(F6.2)' or just 'F6.2'. This is an intent(in) and optional argument.
  Contains the edit descriptor to format value into a string, for example '(F6.2)' or '(f6.2)'. to_string will automatically enclose format in a set of parentheses, so passing F6.2 or f6.2 as format is possible as well.

Result value

The result is an allocatable length character scalar with up to 128 cached character length.

Example

{!example/strings/example_to_string.f90!}

to_c_char

Description

Convert a Fortran character string or a type(string_type) variable to a C character array.
This function converts a Fortran string into a C-style array of characters, ensuring proper null-termination for use in C functions or libraries.

Syntax

cstr = [[stdlib_strings(module):to_c_char(function)]] (value)

Status

Experimental

Class

Pure function.

Argument

• value: Shall be a character(len=*) string or a type(string_type) variable. It is an intent(in) argument.
  This Fortran variable will be converted to a C character array.

Result value

The result is a character(kind=c_char) array with a dimension of len(value) + 1 to accommodate the null terminator.

Example

{!example/strings/example_to_c_char.f90!}