String Formatting in Co-array Fortran

program string_formatting
  use iso_fortran_env
  implicit none

  type :: point
    integer :: x, y
  end type point

  type(point) :: p
  character(len=30) :: s

  ! Initialize the point
  p = point(1, 2)

  ! Print the struct
  print '(A,I0,A,I0,A)', 'struct1: {', p%x, ' ', p%y, '}'

  ! Print the struct with field names
  print '(A,I0,A,I0,A)', 'struct2: {x:', p%x, ' y:', p%y, '}'

  ! Print the type
  print '(A)', 'type: point'

  ! Print boolean
  print '(A,L1)', 'bool: ', .true.

  ! Print integer
  print '(A,I0)', 'int: ', 123

  ! Print binary representation
  print '(A,B0)', 'bin: ', 14

  ! Print character
  print '(A,A1)', 'char: ', achar(33)

  ! Print hexadecimal
  print '(A,Z0)', 'hex: ', 456

  ! Print float
  print '(A,F0.6)', 'float1: ', 78.9

  ! Print scientific notation
  print '(A,ES12.6)', 'float2: ', 123400000.0
  print '(A,ES12.6)', 'float3: ', 123400000.0

  ! Print string
  print '(A,A)', 'str1: ', '"string"'

  ! Print quoted string
  print '(A,A)', 'str2: ', '"""string"""'

  ! Print hexadecimal representation of string
  print '(A,Z2.2,Z2.2,Z2.2,Z2.2)', 'str3: ', iachar('h'), iachar('e'), iachar('x'), iachar(' ')

  ! Print pointer (address not directly accessible in Fortran)
  print '(A)', 'pointer: Not directly accessible in Fortran'

  ! Print with width
  print '(A,I6,I6)', 'width1: |', 12, 345

  ! Print float with width and precision
  print '(A,F6.2,F6.2)', 'width2: |', 1.2, 3.45

  ! Left-justified float
  print '(A,F6.2,F6.2)', 'width3: |', 1.2, 3.45

  ! Print string with width
  print '(A,A6,A6)', 'width4: |', 'foo', 'b'

  ! Left-justified string
  print '(A,A6,A6)', 'width5: |', 'foo', 'b'

  ! Equivalent to Sprintf
  write(s, '(A,A)') 'sprintf: a ', 'string'
  print '(A)', trim(s)

  ! Equivalent to Fprintf
  write(error_unit, '(A,A)') 'io: an ', 'error'

end program string_formatting

This Co-array Fortran program demonstrates various string formatting techniques. Here are some key points:

Fortran uses format specifiers for printing, which are similar to the format verbs in other languages.
The print statement is used for standard output, while write can be used for other units (like error_unit for standard error).
Fortran doesn’t have a built-in struct type, so we define a custom type point.
Some concepts like pointers and hexadecimal representation of strings are not directly available in Fortran, so alternatives or explanations are provided.
Fortran uses different format specifiers for different data types. For example, ‘I’ for integers, ‘F’ for floats, ‘ES’ for scientific notation, etc.
String manipulation in Fortran is somewhat different from other languages. Strings are fixed-length by default, and we use the trim function to remove trailing spaces.
Fortran doesn’t have a direct equivalent to sprintf, but we can use internal writes to achieve similar functionality.
Error output is directed to the predefined error_unit.

This program covers most of the formatting examples from the original, adapted to Fortran’s syntax and capabilities.

String Functions in Co-array Fortran

Text Templates in Co-array Fortran

Learn X By Example

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String Formatting in Co-array Fortran