Merge pull request #733 from jalvesz/master

faster to_lower and to_upper

Author: jvdp1

src/stdlib_ascii.fypp

@@ -223,31 +223,27 @@ contains
  pure function char_to_lower(c) result(t)
  character(len=1), intent(in) :: c !! A character.
  character(len=1) :: t
+ integer, parameter :: wp= iachar('a')-iachar('A'), BA=iachar('A'), BZ=iachar('Z')
  integer :: k
+ !Check whether the integer equivalent is between BA=65 and BZ=90
+ k = ichar(c) 
+ if (k>=BA.and.k<=BZ) k = k + wp 
+ t = char(k)
 
- k = index( uppercase, c )
-
- if ( k > 0 ) then
- t = lowercase(k:k)
- else
- t = c
- endif
  end function char_to_lower
 
  !> Returns the corresponding uppercase letter, if `c` is a lowercase
  !> ASCII character, otherwise `c` itself.
  pure function char_to_upper(c) result(t)
  character(len=1), intent(in) :: c !! A character.
  character(len=1) :: t
+ integer, parameter :: wp= iachar('a')-iachar('A'), la=iachar('a'), lz=iachar('z')
  integer :: k
+ !Check whether the integer equivalent is between la=97 and lz=122
+ k = ichar(c) 
+ if (k>=la.and.k<=lz) k = k - wp 
+ t = char(k)
 
- k = index( lowercase, c )
-
- if ( k > 0 ) then
- t = uppercase(k:k)
- else
- t = c
- endif
  end function char_to_upper
 
  !> Convert character variable to lower case