Added to_lower, to_upper, reverse and to_title function to stdlib_string_type.f90 file

README.md

@@ -138,7 +138,7 @@ To test your build, run the test suite after the build has finished with
 cmake --build build --target test
 ```
 
-Please report failing tests on our [issue tracker](https://github.com/fortran-lang/stdlib/issues/new/choose) including details on the compiler used, the operating system and platform architecture.
+Please report failing tests on our [issue tracker](https://github.com/fortran-lang/stdlib/issues/new/choose) including details of the compiler used, the operating system and platform architecture.
 
 To install the project to the declared prefix run
 

src/Makefile.manual

@@ -109,3 +109,4 @@ stdlib_stats_var.o: \
 stdlib_stats_distribution_PRNG.o: \
         stdlib_kinds.o \
 	stdlib_error.o
+stdlib_string_type.o: stdlib_ascii.o

src/stdlib_ascii.f90

@@ -64,6 +64,36 @@ module stdlib_ascii
     character(len=*), public, parameter :: lowercase = letters(27:) !! a .. z
     character(len=*), public, parameter :: whitespace = " "//TAB//VT//CR//LF//FF !! ASCII _whitespace
 
+
+    !> Returns a new character sequence which is the lower case 
+    !> version of the input character sequence
+    !> This method is pure and returns a character sequence
+    interface to_lower
+        module procedure :: to_lower
+    end interface to_lower
+
+    !> Returns a new character sequence which is the upper case
+    !> version of the input character sequence
+    !> This method is pure and returns a character sequence
+    interface to_upper
+        module procedure :: to_upper
+    end interface to_upper
+
+    !> Returns a new character sequence which is the titled
+    !> version of the input character sequence
+    !> This method is pure and returns a character sequence
+    interface to_title
+        module procedure :: to_title
+    end interface to_title
+
+    !> Returns a new character sequence which is the reversed
+    !> version of the input charater sequence
+    !> This method is pure and returns a character sequence
+    interface reverse
+        module procedure :: reverse
+    end interface reverse
+
+
 contains
 
     !> Checks whether `c` is an ASCII letter (A .. Z, a .. z).

src/stdlib_string_type.f90

@@ -12,11 +12,15 @@
 !>
 !> The specification of this module is available [here](../page/specs/stdlib_string_type.html).
 module stdlib_string_type
+    use stdlib_ascii, only: to_lower_ => to_lower, to_upper_ => to_upper, &
+                            to_title_ => to_title, reverse_ => reverse
+
     implicit none
     private
 
     public :: string_type
-    public :: len, len_trim, trim, index, scan, verify, repeat, adjustr, adjustl
+    public :: len, len_trim, trim, index, scan, verify, repeat, adjustr, &
+              adjustl, to_lower, to_upper, to_title, reverse
     public :: lgt, lge, llt, lle, char, ichar, iachar
     public :: assignment(=)
     public :: operator(>), operator(>=), operator(<), operator(<=)
@@ -89,6 +93,38 @@ module stdlib_string_type
         module procedure :: repeat_string
     end interface repeat
 
+    !> Convert the character sequence hold by the input string to lower case
+    !>
+    !> This method is Elemental and returns a new string_type instance which holds lowercase
+    !> version of the character sequence hold by the input string
+    interface to_lower
+        module procedure :: to_lower_string
+    end interface to_lower
+
+    !> Convert the character sequence hold by the input string to upper case
+    !>
+    !> This method is Elemental and returns a new string_type instance which holds uppercase
+    !> version of the character sequence hold by the input string
+    interface to_upper
+        module procedure :: to_upper_string
+    end interface to_upper
+
+    !> Convert the character sequence hold by the input string to title case
+    !>
+    !> This method is Elemental and returns a new string_type instance which holds titlecase
+    !> version of the character sequence hold by the input string
+    interface to_title
+        module procedure :: to_title_string
+    end interface to_title
+
+    !> Reverse the character sequence hold by the input string
+    !> 
+    !> This method is Elemental and returns a new string_type instance which holds reversed
+    !> sequence of the character sequence hold by the input string
+    interface reverse
+        module procedure :: reverse_string
+    end interface reverse
+
     !> Return the character sequence represented by the string.
     !>
     !> This method is elemental and returns a scalar character value.
@@ -447,6 +483,46 @@ elemental function repeat_string(string, ncopies) result(repeated_string)
     end function repeat_string
 
 
+    !> Convert the character sequence hold by the input string to lower case
+    elemental function to_lower_string(string) result(lowercase_string)
+        type(string_type), intent(in) :: string
+        type(string_type) :: lowercase_string
+
+        lowercase_string%raw = to_lower_(maybe(string))
+
+    end function to_lower_string
+
+
+    !> Convert the character sequence hold by the input string to upper case
+    elemental function to_upper_string(string) result(uppercase_string)
+        type(string_type), intent(in) :: string
+        type(string_type) :: uppercase_string
+
+        uppercase_string%raw = to_upper_(maybe(string))
+
+    end function to_upper_string
+
+
+    !> Convert the character sequence hold by the input string to title case
+    elemental function to_title_string(string) result(titlecase_string)
+        type(string_type), intent(in) :: string
+        type(string_type) :: titlecase_string
+
+        titlecase_string%raw = to_title_(maybe(string))
+
+    end function to_title_string
+
+
+    !> Reverse the character sequence hold by the input string
+    elemental function reverse_string(string) result(reversed_string)
+        type(string_type), intent(in) :: string
+        type(string_type) :: reversed_string
+
+        reversed_string%raw = reverse_(maybe(string))
+
+    end function reverse_string
+
+
     !> Position of a sequence of character within a character sequence.
     !> In this version both character sequences are represented by a string.
     elemental function index_string_string(string, substring, back) result(pos)

src/tests/string/test_string_functions.f90

@@ -0,0 +1,58 @@
+! SPDX-Identifier: MIT
+module test_string_functions
+    use stdlib_error, only : check
+    use stdlib_string_type, only : string_type, assignment(=), operator(==), &
+                                    to_lower, to_upper, to_title, reverse
+    implicit none
+
+contains
+
+    subroutine test_to_lower_string
+        type(string_type) :: test_string, compare_string
+        test_string = "To_LoWEr !$%-az09AZ"
+        compare_string = "to_lower !$%-az09az"
+
+        call check(to_lower(test_string) == compare_string)
+
+    end subroutine test_to_lower_string
+
+    subroutine test_to_upper_string
+        type(string_type) :: test_string, compare_string
+        test_string = "To_UpPeR !$%-az09AZ"
+        compare_string = "TO_UPPER !$%-AZ09AZ"
+
+        call check(to_upper(test_string) == compare_string)
+
+    end subroutine test_to_upper_string
+
+    subroutine test_to_title_string
+        type(string_type) :: test_string, compare_string
+        test_string = "_#To tiTlE !$%-az09AZ"
+        compare_string = "_#To title !$%-a09az"
+
+        call check(to_title(test_string) == compare_string)
+
+    end subroutine test_to_title_string
+
+    subroutine test_reverse_string
+        type(string_type) :: test_string, compare_string
+        test_string = "_To ReVerSe !$%-az09AZ   "
+        compare_string = "   ZA90za-%$! eSreVeR oT_"
+
+        call check(reverse(test_string) == compare_string)
+
+    end subroutine test_reverse_string
+
+end module test_string_functions
+
+
+program tester
+    use test_string_functions
+    implicit none
+
+    call test_to_lower_string
+    call test_to_upper_string
+    call test_to_title_string
+    call test_reverse_string
+
+end program tester