Fix pure/elemental in string_type

Author: zoziha

doc/specs/stdlib_string_type.md

@@ -528,7 +528,7 @@ Return the character sequence represented by the string.
 
 #### Class
 
-Pure function.
+Elemental function.
 
 #### Argument
 
@@ -618,7 +618,7 @@ Return a substring from the character sequence of the string.
 
 #### Class
 
-Pure function.
+Elemental function.
 
 #### Argument
 
@@ -1993,7 +1993,7 @@ An unallocated `string_type` instance is equivalent to an empty string.
 
 #### Class
 
-Pure Subroutine.
+Pure subroutine (Elemental subroutine, only when both `from` and `to` are `type(string_type)`)
 
 #### Argument
 

src/stdlib_string_type.fypp

@@ -52,18 +52,18 @@ module stdlib_string_type
 
     !> Constructor for new string instances
     interface string_type
-        pure elemental module function new_string(string) result(new)
+        elemental module function new_string(string) result(new)
             character(len=*), intent(in), optional :: string
             type(string_type) :: new
         end function new_string
         #:for kind in INT_KINDS
-        pure elemental module function new_string_from_integer_${kind}$(val) result(new)
+        elemental module function new_string_from_integer_${kind}$(val) result(new)
             integer(${kind}$), intent(in) :: val
             type(string_type) :: new
         end function new_string_from_integer_${kind}$
         #:endfor
         #:for kind in LOG_KINDS
-        pure elemental module function new_string_from_logical_${kind}$(val) result(new)
+        elemental module function new_string_from_logical_${kind}$(val) result(new)
             logical(${kind}$), intent(in) :: val
             type(string_type) :: new
         end function new_string_from_logical_${kind}$
@@ -438,7 +438,7 @@ contains
 
 
     !> Return the character sequence represented by the string.
-    pure function char_string(string) result(character_string)
+    elemental function char_string(string) result(character_string)
         type(string_type), intent(in) :: string
         character(len=len(string)) :: character_string
 
@@ -457,7 +457,7 @@ contains
     end function char_string_pos
 
     !> Return the character sequence represented by the string.
-    pure function char_string_range(string, start, last) result(character_string)
+    elemental function char_string_range(string, start, last) result(character_string)
         type(string_type), intent(in) :: string
         integer, intent(in) :: start
         integer, intent(in) :: last
@@ -678,7 +678,7 @@ contains
 
     !> Moves the allocated character scalar from 'from' to 'to'
     !> No output
-    subroutine move_string_string(from, to)
+    elemental subroutine move_string_string(from, to)
         type(string_type), intent(inout) :: from
         type(string_type), intent(out) :: to
 
@@ -688,7 +688,7 @@ contains
 
     !> Moves the allocated character scalar from 'from' to 'to'
     !> No output
-    subroutine move_string_char(from, to)
+    pure subroutine move_string_char(from, to)
         type(string_type), intent(inout) :: from
         character(len=:), intent(out), allocatable :: to
 
@@ -698,7 +698,7 @@ contains
 
     !> Moves the allocated character scalar from 'from' to 'to'
     !> No output
-    subroutine move_char_string(from, to)
+    pure subroutine move_char_string(from, to)
         character(len=:), intent(inout), allocatable :: from
         type(string_type), intent(out) :: to
 
@@ -708,7 +708,7 @@ contains
 
     !> Moves the allocated character scalar from 'from' to 'to'
     !> No output
-    subroutine move_char_char(from, to)
+    pure subroutine move_char_char(from, to)
         character(len=:), intent(inout), allocatable :: from
         character(len=:), intent(out), allocatable :: to
 
@@ -1233,7 +1233,7 @@ contains
 
 
     !> Safely return the character sequences represented by the string
-    pure function maybe(string) result(maybe_string)
+    elemental function maybe(string) result(maybe_string)
         type(string_type), intent(in) :: string
         character(len=len(string)) :: maybe_string
         if (allocated(string%raw)) then