add character array example

Author: scivision

character/CMakeLists.txt

@@ -1,6 +1,9 @@
 add_executable(ascii ascii.f90)
 add_test(NAME char:AsciiSpecial COMMAND ascii)
 
+add_executable(character_array character_array.f90)
+add_test(NAME char:array COMMAND character_array)
+
 add_executable(split split_string.f90)
 add_test(NAME char:SplitString COMMAND split)
 

character/README.md

@@ -1,12 +1,22 @@
 # Strings
 
+Strings / character in Fortran is often easier than is commonly thought, as long as the characteristic particular to Fortran are kept in mind.
+These examples aim to raise awareness of how to use `character` type in Fortran.
+
+## character array with dissimilar length
+
+Although it is possible to use `allocatable` character array, the
+[character_array.f90](./character_array.f90)
+example shows the use of fixed lengh `character` array with each element having a distinct length.
+
 ## Split strings about delimiter
 
 This splits a string once around a delimiter:
 
     ./split
 
 And notes that it is probably best to use fixed length CHARACTER longer
-than you'll need. If you're trying to load and parse a complicated text
+than you'll need.
+If you're trying to load and parse a complicated text
 file, it is perhaps better to load that file first in Python, parse it,
 then pass it to Fortran via f2py (load Fortran code as a Python module).

character/ascii.f90

@@ -1,3 +1,8 @@
+program ascii
+!! prints a couple special characters
+
+implicit none
+
 print *,'next is a form feed',achar(12)
 print *,'that was a form feed'
 

character/character_array.f90

@@ -0,0 +1,22 @@
+program character_array
+!! examples of using dissimilar character elements in an array
+!! the general concept is to make the character(len=) the length of the
+!! longest string you will need.
+!! trim() each element when actually used if needed.
+implicit none
+
+!> specify (*) or maximum len=, else each will be length one.
+character(*), parameter :: foo(3) = [character(9) :: 'hi', 'hello', 'greetings']
+!! notice how you have to specify the length inside the array.
+!! this sometimes has to be done for numerical e.g.
+!! mixed integer / real in an array that's actually meant to be real
+real, parameter :: mixed(4) = [real :: 27.232, 1, 2, 5.234]
+
+character(9) :: bar(3)
+
+bar = foo
+
+if (.not. all(bar==foo)) error stop
+
+
+end program

character/charlen.f90

@@ -1,10 +1,14 @@
-! shows how to properly specify character length and character array
+program charlen
+!! shows how to properly specify character length and character array
+implicit none
 
-character*(5) :: cb5  ! obsolete, don't use
-character(5)  :: c5   ! good to use
-character(*),parameter  :: ca(2)='hello'
+character*(5) :: cb5  !< obsolete, don't use
 
-if (.not.all([len(cb5)==5,len(c5)==5,len(ca)==5,size(ca)==2])) error stop
+!>  good to use
+character(5)  :: c5
+character(*), parameter :: ca(2) = ['hello', 'sorry']
+
+if (.not.all([len(cb5)==5, len(c5)==5, len(ca)==5, size(ca)==2])) error stop
 print *, ca
 
 end program

character/meson.build

@@ -1,35 +1,24 @@
 ascii = executable('ascii', 'ascii.f90')
-test('Ascii Special', ascii,
-  suite: 'char',
-  timeout: 10)
+test('Ascii Special', ascii, suite: 'char', timeout: 10)
+
+char_array = executable('character_array', 'character_array.f90')
+test('CharacterArray', char_array, suite: 'char', timeout: 10)
 
 split = executable('split', 'split_string.f90')
-test('Split Character', split,
-  suite: 'char',
-  timeout: 10)
+test('Split Character', split, suite: 'char', timeout: 10)
 
 printorwrite = executable('printorwrite', 'print_vs_write.f90')
-test('UTF8', printorwrite,
-  suite: 'char',
-  timeout: 10)
+test('UTF8', printorwrite, suite: 'char', timeout: 10)
 
 str2int = executable('str2int', 'str2int.f90')
-test('Str2Int', str2int,
-  suite: 'char',
-  timeout: 10)
+test('Str2Int', str2int, suite: 'char', timeout: 10)
 
 special_char = executable('special_char', 'special_characters.f90')
-test('Special Characters', special_char,
-  suite: 'char',
-  timeout: 10)
+test('Special Characters', special_char, suite: 'char', timeout: 10)
 
 charlen = executable('charlen', 'charlen.f90')
-test('Character Len', charlen,
-  suite: 'char',
-  timeout: 10)
+test('Character Len', charlen, suite: 'char', timeout: 10)
 
 overwrite_stdout = executable('overwrite_stdout', 'overwrite_stdout.f90',
   link_with: sleep_std)
-test('Overwrite Stdout', overwrite_stdout,
-  suite: 'char',
-  timeout: 10)
+test('Overwrite Stdout', overwrite_stdout, suite: 'char', timeout: 10)

character/overwrite_stdout.f90

@@ -1,5 +1,6 @@
-! overwrites terminal stdout in place e.g. for update status
-! char(13) is carriage return
+program overwrite_stdout
+!! overwrites terminal stdout in place e.g. for update status
+!! char(13) is carriage return
 use, intrinsic:: iso_c_binding, only: c_int
 use, intrinsic:: iso_fortran_env, only: stdout=>output_unit
 use sleep_std, only : sleep

character/print_vs_write.f90

@@ -1,3 +1,4 @@
+program print_vs_write
 !! Fortran 2003 standard states that
 !!  print *,
 !!  write (*,*)

character/special_characters.f90

@@ -1,7 +1,10 @@
+program special_characters
 !! This program shows a few special ASCII characters in Fortran.
 !! https://en.wikipedia.org/wiki/ASCII#Character_groups
 
 use iso_c_binding, only: c_null_char
+implicit none
+
 character, parameter :: &
 nul = c_null_char, &
 etx = char(3), &

character/split_string.f90

@@ -1,9 +1,4 @@
-! split a string about a delimiter token, return part before delim
-!
-! with regard to length of CHARACTER, it's probably best to pick a length longer than you'll need
-! and trim rather than using assumed size, particularly if interfacing with other languages
-! CHARACTER assumed size seems to work, but is not reliable in diverse enviroments.
-! Your time is more valueable than a few bytes of RAM.
+!! split a string about a delimiter token, return part before delim
 
 module strutils
 
@@ -27,14 +22,16 @@ end function split
 end module strutils
 
 
+program split_string
 use strutils, only: split
+implicit none
 
 character(*),parameter :: mystr="hello.txt"
 character(:),allocatable :: stem
 
 stem = split(mystr,'.')
 print '(A)', stem
 
-if(len(stem) /= 5) error stop 'allocatable character of unexpected length'
+if (len(stem) /= 5) error stop 'allocatable character of unexpected length'
 
 end program