stdlib_string_type:local:
:depth: 2
The stdlib_string_type provides a derived type holding an arbitrary sequence
of characters compatible with most Fortran intrinsic character procedures as
well as operators for working with character variables and constants.
The generated API reference for this pilot module is available in
[the Sphinx API section](/stdlib/doc/api/stdlib_string_type.rst).
string_type derived typeThe string_type is defined as a non-extendible derived type representing a
sequence of characters. The internal representation of the character sequence
is implementation dependent and not visible for the user of the module.
Experimental
Procedures returning string_type instances can usually be used in elemental
context, while procedures returning scalar character values can only be
used in a pure way.
Experimental
The module defines a constructor to create an empty string type.
Creates a string instance representing an empty string.
res = string_type ` ()`
Elemental function.
None.
The result is an instance of string_type with zero length.
```{literalinclude} ../../example/string_type/example_constructor_empty.f90 :language: fortran
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### Constructor from character scalar
#### Status
Experimental
#### Description
The module defines a constructor to create a string type from a character scalar.
Creates a string instance representing the input character scalar value.
The constructor shall create an empty string if an unallocated deferred-length
character variable is passed.
#### Syntax
`res = ` `string_type` ` (string)`
#### Class
Elemental function.
#### Argument
`string`: shall be a scalar character value. It is an `intent(in)` argument.
#### Result value
The result is an instance of `string_type`.
#### Example
```{literalinclude} ../../example/string_type/example_constructor_scalar.f90
:language: fortran
Experimental
The module defines a constructor to create a string type from an integer scalar.
res = string_type ` (string)`
Elemental function.
val: shall be a scalar integer value. It is an intent(in) argument.
The result is an instance of string_type.
```{literalinclude} ../../example/string_type/example_constructor_integer.f90 :language: fortran
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### Constructor from logical scalar
#### Status
Experimental
#### Description
The module defines a constructor to create a string type from a logical scalar.
#### Syntax
`res = ` `string_type` ` (string)`
#### Class
Elemental function.
#### Argument
`val`: shall be a scalar logical value. It is an `intent(in)` argument.
#### Result value
The result is an instance of `string_type`.
#### Example
```{literalinclude} ../../example/string_type/example_constructor_logical.f90
:language: fortran
Experimental
The module defines an assignment operations, =, to create a string type
from a character scalar.
Creates a string instance representing the right-hand-side character scalar value.
lhs = rhs
Elemental subroutine, assignment(=).
```{literalinclude} ../../example/string_type/example_constructor_character.f90 :language: fortran
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### Len function
#### Status
Experimental
#### Description
Returns the length of the string.
#### Syntax
`res = ` `len` ` (string)`
#### Class
Elemental function.
#### Argument
`string`: Instance of a `string_type`. This argument is `intent(in)`.
#### Result value
The result is a default integer scalar value.
#### Example
```{literalinclude} ../../example/string_type/example_len.f90
:language: fortran
Experimental
Returns the length of the character sequence without trailing spaces represented by the string.
res = len_trim ` (string)`
Elemental function.
string: Instance of a string_type. This argument is intent(in).
The result is a default integer scalar value.
```{literalinclude} ../../example/string_type/example_len_trim.f90 :language: fortran
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### Trim function
#### Status
Experimental
#### Description
Returns the character sequence hold by the string without trailing spaces
represented by a `string_type`.
#### Syntax
`res = ` `trim` ` (string)`
#### Class
Elemental function.
#### Argument
- `string`: Instance of a `string_type`. This argument is `intent(in)`.
#### Result value
The result is a scalar `string_type` value.
#### Example
```{literalinclude} ../../example/string_type/example_trim.f90
:language: fortran
Experimental
Left-adjust the character sequence represented by the string. The length of the character sequence remains unchanged.
res = adjustl ` (string)`
Elemental function.
string: Instance of a string_type. This argument is intent(in).The result is a scalar string_type value.
```{literalinclude} ../../example/string_type/example_adjustl.f90 :language: fortran
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### Adjustr function
#### Status
Experimental
#### Description
Right-adjust the character sequence represented by the string.
The length of the character sequence remains unchanged.
#### Syntax
`res = ` `adjustr` ` (string)`
#### Class
Elemental function.
#### Argument
- `string`: Instance of a `string_type`. This argument is `intent(in)`.
#### Result value
The result is a scalar `string_type` value.
#### Example
```{literalinclude} ../../example/string_type/example_adjustr.f90
:language: fortran
Experimental
Repeats the character sequence hold by the string by the number of specified copies.
res = repeat ` (string, ncopies)`
Elemental function.
string: Instance of a string_type. This argument is intent(in).ncopies: Integer of default type. This argument is intent(in).The result is a scalar string_type value.
```{literalinclude} ../../example/string_type/example_repeat.f90 :language: fortran
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### Char function
#### Status
Experimental
#### Description
Return the character sequence represented by the string.
#### Syntax
`res = ` `char` ` (string)`
#### Class
Pure function.
#### Argument
- `string`: Instance of a `string_type`. This argument is `intent(in)`.
#### Result value
The result is a scalar character value.
#### Example
```{literalinclude} ../../example/string_type/example_char.f90
:language: fortran
Experimental
Return the character at a certain position in the string.
res = char ` (string, pos)`
Elemental function.
string: Instance of a string_type. This argument is intent(in).pos: Integer of default type. This argument is intent(in).The result is a scalar character value.
```{literalinclude} ../../example/string_type/example_char_position.f90 :language: fortran
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### Char function (range variant)
#### Status
Experimental
#### Description
Return a substring from the character sequence of the string.
#### Syntax
`res = ` `char` ` (string, start, last)`
#### Class
Pure function.
#### Argument
- `string`: Instance of a `string_type`. This argument is `intent(in)`.
- `start`: Integer of default type. This argument is `intent(in)`.
- `last`: Integer of default type. This argument is `intent(in)`.
#### Result value
The result is a scalar character value.
#### Example
```{literalinclude} ../../example/string_type/example_char_range.f90
:language: fortran
Experimental
Character-to-integer conversion function.
Returns the code for the character in the first character position of the character sequence in the system’s native character set.
res = ichar ` (string)`
Elemental function.
string: Instance of a string_type. This argument is intent(in).The result is a default integer scalar value.
```{literalinclude} ../../example/string_type/example_ichar.f90 :language: fortran
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### Iachar function
#### Status
Experimental
#### Description
Code in ASCII collating sequence.
Returns the code for the ASCII character in the first character position of
the character sequences represent by the string.
#### Syntax
`res = ` `iachar` ` (string)`
#### Class
Elemental function.
#### Argument
- `string`: Instance of a `string_type`. This argument is `intent(in)`.
#### Result value
The result is a default integer scalar value.
#### Example
```{literalinclude} ../../example/string_type/example_iachar.f90
:language: fortran
Experimental
Position of a substring within a string.
Returns the position of the start of the leftmost or rightmost occurrence of string substring in string, counting from one. If substring is not present in string, zero is returned.
res = index ` (string, substring[, back])`
Elemental function.
string: Either scalar character value or string type. This argument is intent(in).substring: Either scalar character value or string type. This argument is intent(in).back: Either absent or a scalar logical value. This argument is intent(in).The result is a default integer scalar value.
```{literalinclude} ../../example/string_type/example_index.f90 :language: fortran
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### Scan function
#### Status
Experimental
#### Description
Scans a *string* for the presence any of the characters in a *set* of characters.
If *back* is either absent or *false*, this function returns the position
of the leftmost character of *string* that is in *set*. If *back* is *true*,
the rightmost position is returned. If no character of *set* is found in
*string*, the result is zero.
#### Syntax
`res = ` `scan` ` (string, set[, back])`
#### Class
Elemental function.
#### Argument
- `string`: Either scalar character value or string type. This argument is `intent(in)`.
- `set`: Either scalar character value or string type. This argument is `intent(in)`.
- `back`: Either absent or a scalar logical value. This argument is `intent(in)`.
#### Result value
The result is a default integer scalar value.
#### Example
```{literalinclude} ../../example/string_type/example_scan.f90
:language: fortran
Experimental
Verifies that all the characters in string belong to the set of characters in set. If back is either absent or false, this function returns the position of the leftmost character of string that is not in set. If back is true, the rightmost position is returned. If all characters of string are found in set, the result is zero.
res = verify ` (string, set[, back])`
Elemental function.
string: Either scalar character value or string type. This argument is intent(in).set: Either scalar character value or string type. This argument is intent(in).back: Either absent or a scalar logical value. This argument is intent(in).The result is a default integer scalar value.
```{literalinclude} ../../example/string_type/example_verify.f90 :language: fortran
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### Lgt function (lexical greater than)
#### Status
Experimental
#### Description
Lexically compare the order of two character sequences being greater than.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic `lgt` procedure.
#### Syntax
`res = ` `lgt` ` (lhs, rhs)`
#### Class
Elemental function.
#### Argument
- `lhs`: Either scalar character value or string type. This argument is `intent(in)`.
- `rhs`: Either scalar character value or string type. This argument is `intent(in)`.
#### Result value
The result is a default logical scalar value.
#### Example
```{literalinclude} ../../example/string_type/example_lgt.f90
:language: fortran
Experimental
Lexically compare the order of two character sequences being less than.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic llt procedure.
res = llt ` (lhs, rhs)`
Elemental function.
lhs: Either scalar character value or string type. This argument is intent(in).rhs: Either scalar character value or string type. This argument is intent(in).The result is a default logical scalar value.
```{literalinclude} ../../example/string_type/example_llt.f90 :language: fortran
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### Lge function (lexical greater than or equal)
#### Status
Experimental
#### Description
Lexically compare the order of two character sequences being greater than
or equal.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic `lge` procedure.
#### Syntax
`res = ` `lge` ` (lhs, rhs)`
#### Class
Elemental function.
#### Argument
- `lhs`: Either scalar character value or string type. This argument is `intent(in)`.
- `rhs`: Either scalar character value or string type. This argument is `intent(in)`.
#### Result value
The result is a default logical scalar value.
#### Example
```{literalinclude} ../../example/string_type/example_lge.f90
:language: fortran
Experimental
Lexically compare the order of two character sequences being less than or equal.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic lle procedure.
res = lle ` (lhs, rhs)`
Elemental function.
lhs: Either scalar character value or string type. This argument is intent(in).rhs: Either scalar character value or string type. This argument is intent(in).The result is a default logical scalar value.
```{literalinclude} ../../example/string_type/example_lle.f90 :language: fortran
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### To\_lower function
#### Status
Experimental
#### Description
Returns a new string_type instance which holds the lowercase version of the
character sequence hold by the input string.
#### Syntax
`lowercase_string = ` `to_lower` ` (string)`
#### Class
Elemental function.
#### Argument
`string`: Instance of `string_type`. This argument is `intent(in)`.
#### Result Value
The result is a scalar `string_type` value.
#### Example
```{literalinclude} ../../example/string_type/example_to_lower.f90
:language: fortran
Experimental
Returns a new string_type instance which holds the uppercase version of the character sequence hold by the input string.
uppercase_string = to_upper ` (string)`
Elemental function.
string: Instance of string_type. This argument is intent(in).
The result is a scalar string_type value.
```{literalinclude} ../../example/string_type/example_to_upper.f90 :language: fortran
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### To\_title function
#### Status
Experimental
#### Description
Returns a new string_type instance which holds the titlecase version
of the character sequence hold by the input string.
Title case: First character of every word in the sentence is converted to
uppercase and the rest of the characters are converted to lowercase.
A word is a contiguous sequence of character(s) which consists of alphabetical
character(s) and numeral(s) only and doesn't exclude any alphabetical character
or numeral present next to either of its 2 ends.
#### Syntax
`titlecase_string = ` `to_title` ` (string)`
#### Class
Elemental function.
#### Argument
`string`: Instance of `string_type`. This argument is `intent(in)`.
#### Result Value
The result is a scalar `string_type` value.
#### Example
```{literalinclude} ../../example/string_type/example_to_title.f90
:language: fortran
Experimental
Returns a new string_type instance which holds the sentencecase version of the character sequence hold by the input string. Sentencecase version: The first alphabetical character of the input character sequence is transformed to uppercase unless it follows a numeral and the rest of the characters in the sequence are transformed to lowercase.
sentencecase_string = to_sentence ` (string)`
Elemental function.
string: Instance of string_type. This argument is intent(in).
The result is a scalar string_type value.
```{literalinclude} ../../example/string_type/example_to_sentence.f90 :language: fortran
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### Reverse function
#### Status
Experimental
#### Description
Returns a new string_type instance which holds the reversed version of the
character sequence hold by the input string.
#### Syntax
`reverse_string = ` `reverse` ` (string)`
#### Class
Elemental function.
#### Argument
`string`: Instance of `string_type`. This argument is `intent(in)`.
#### Result Value
The result is a scalar `string_type` value.
#### Example
```{literalinclude} ../../example/string_type/example_reverse.f90
:language: fortran
Experimental
Compare the order of two character sequences being greater.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic operator(>)
and operator(.gt.).
res = lhs > rhs
res = lhs .gt. rhs
Elemental function, operator(>) and operator(.gt.).
lhs: Either scalar character value or string type. This argument is intent(in).rhs: Either scalar character value or string type. This argument is intent(in).The result is a default logical scalar value.
```{literalinclude} ../../example/string_type/example_gt.f90 :language: fortran
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### Comparison operator less
#### Status
Experimental
#### Description
Compare the order of two character sequences being less.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic `operator(<)`
and `operator(.lt.)`.
#### Syntax
`res = lhs < rhs`
`res = lhs .lt. rhs`
#### Class
Elemental function, `operator(<)` and `operator(.lt.)`.
#### Argument
- `lhs`: Either scalar character value or string type. This argument is `intent(in)`.
- `rhs`: Either scalar character value or string type. This argument is `intent(in)`.
#### Result value
The result is a default logical scalar value.
#### Example
```{literalinclude} ../../example/string_type/example_lt.f90
:language: fortran
Experimental
Compare the order of two character sequences being greater or equal.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic operator(>=)
and operator(.ge.).
res = lhs >= rhs
res = lhs .ge. rhs
Elemental function, operator(>=) and operator(.ge.).
lhs: Either scalar character value or string type. This argument is intent(in).rhs: Either scalar character value or string type. This argument is intent(in).The result is a default logical scalar value.
```{literalinclude} ../../example/string_type/example_ge.f90 :language: fortran
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### Comparison operator less or equal
#### Status
Experimental
#### Description
Compare the order of two character sequences being less or equal.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic `operator(<=)`
and `operator(.le.)`.
#### Syntax
`res = lhs <= rhs`
`res = lhs .le. rhs`
#### Class
Elemental function, `operator(<=)` and `operator(.le.)`.
#### Argument
- `lhs`: Either scalar character value or string type. This argument is `intent(in)`.
- `rhs`: Either scalar character value or string type. This argument is `intent(in)`.
#### Result value
The result is a default logical scalar value.
#### Example
```{literalinclude} ../../example/string_type/example_le.f90
:language: fortran
Experimental
Compare two character sequences for equality.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic operator(==)
and operator(.eq.).
res = lhs == rhs
res = lhs .eq. rhs
Elemental function, operator(==) and operator(.eq.).
lhs: Either scalar character value or string type. This argument is intent(in).rhs: Either scalar character value or string type. This argument is intent(in).The result is a default logical scalar value.
```{literalinclude} ../../example/string_type/example_eq.f90 :language: fortran
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### Comparison operator not equal
#### Status
Experimental
#### Description
Compare two character sequences for inequality.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic `operator(/=)`
and `operator(.ne.)`.
#### Syntax
`res = lhs /= rhs`
`res = lhs .ne. rhs`
#### Class
Elemental function, `operator(/=)` and `operator(.ne.)`.
#### Argument
- `lhs`: Either scalar character value or string type. This argument is `intent(in)`.
- `rhs`: Either scalar character value or string type. This argument is `intent(in)`.
#### Result value
The result is a default logical scalar value.
#### Example
```{literalinclude} ../../example/string_type/example_ne.f90
:language: fortran
Experimental
Concatenate two character sequences.
The left-hand side, the right-hand side or both character sequences can
be represented by a string type.
This defines three procedures overloading the intrinsic operator(//).
res = lhs // rhs
Elemental function, operator(//).
lhs: Either scalar character value or string type. This argument is intent(in).rhs: Either scalar character value or string type. This argument is intent(in).The result is an instance of string_type.
```{literalinclude} ../../example/string_type/example_cont.f90 :language: fortran
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### Unformatted write
#### Status
Experimental
#### Description
Write the character sequence hold by the string to a connected unformatted unit.
The character sequences is represented by an 64 bit signed integer record,
holding the length of the following character record.
#### Syntax
`write(unit, iostat=iostat, iomsg=iomsg) string`
#### Class
Unformatted user defined derived type output.
#### Argument
- `string`: Instance of the string type to read. This argument is `intent(inout)`.
- `unit`: Formatted unit for output. This argument is `intent(in)`.
- `iostat`: Status identifier to indicate success of output operation.
This argument is `intent(out)`.
- `iomsg`: Buffer to return error message in case of failing output operation.
This argument is `intent(inout)`.
#### Example
```{literalinclude} ../../example/string_type/example_uwrite.f90
:language: fortran
Experimental
Write the character sequence hold by the string to a connected formatted unit.
The current implementation is limited to list directed output and dt formatted
output. Requesting namelist output will raise an error.
write(unit, fmt, iostat=iostat, iomsg=iomsg) string
Formatted user defined derived type output.
string: Instance of the string type to read. This argument is intent(inout).unit: Formatted unit for output. This argument is intent(in).iotype: Type of formatted data transfer, has the value "LISTDIRECTED" for fmt=*,
"NAMELIST" for namelist output or starts with "DT" for derived type output.
This argument is intent(in).v_list: Rank one array of default integer type containing the edit descriptors for
derived type output.
This argument is intent(in).iostat: Status identifier to indicate success of output operation.
This argument is intent(out).iomsg: Buffer to return error message in case of failing output operation.
This argument is intent(inout).```{literalinclude} ../../example/string_type/example_fwrite.f90 :language: fortran
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### Unformatted read
#### Status
Experimental
#### Description
Read a character sequence from a connected unformatted unit into the string.
The character sequences is represented by an 64 bit signed integer record,
holding the length of the following character record.
On failure the state the read variable is undefined and implementation dependent.
#### Syntax
`read(unit, iostat=iostat, iomsg=iomsg) string`
#### Class
Unformatted derived type input.
#### Argument
- `string`: Instance of the string type to read. This argument is `intent(inout)`.
- `unit`: Formatted unit for input. This argument is `intent(in)`.
- `iostat`: Status identifier to indicate success of input operation.
This argument is `intent(out)`.
- `iomsg`: Buffer to return error message in case of failing input operation.
This argument is `intent(inout)`.
#### Example
```{literalinclude} ../../example/string_type/example_uread.f90
:language: fortran
Experimental
Read a character sequence from a connected formatted unit into the string. List-directed input will retrieve the complete record into the string.
On failure the state the read variable is undefined and implementation dependent.
The current implementation is limited to list directed input.
Requesting dt formatted input or namelist output will raise an error.
read(unit, fmt, iostat=iostat, iomsg=iomsg) string
Formatted derived type input.
string: Instance of the string type to read. This argument is intent(inout).unit: Formatted unit for input. This argument is intent(in).iotype: Type of formatted data transfer, has the value "LISTDIRECTED" for fmt=*,
"NAMELIST" for namelist input or starts with "DT" for derived type input.
This argument is intent(in).v_list: Rank one array of default integer type containing the edit descriptors for
derived type input.
This argument is intent(in).iostat: Status identifier to indicate success of input operation.
This argument is intent(out).iomsg: Buffer to return error message in case of failing input operation.
This argument is intent(inout).```{literalinclude} ../../example/string_type/example_fread.f90 :language: fortran
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### move
#### Status
Experimental
#### Description
Moves the allocation from `from` to `to`, consequently deallocating `from` in this process.
If `from` is not allocated before execution, `to` gets deallocated by the process.
An unallocated `string_type` instance is equivalent to an empty string.
If `from` and `to` are the same variable, then `from` remains unchanged.
#### Syntax
`call ` {f:iface}`move` ` (from, to)`
#### Class
Pure subroutine (Elemental subroutine, only when both `from` and `to` are `type(string_type)`)
#### Argument
- `from`: Character scalar or `string_type`.
This argument is `intent(inout)`.
- `to`: Character scalar or `string_type`.
This argument is `intent(inout)` when both `from` and `to` are `type(string_type)`,
otherwise `intent(out)`.
#### Example
```{literalinclude} ../../example/string_type/example_move.f90
:language: fortran