Fortran

Fortran is a historical imperative and structured language first appearing in 1957.

Hello World

program hello
  ! BEGIN_FRAGLET
  print *, "Hello World!"
  ! END_FRAGLET
end program hello

Coding Guide

Language Version

Fortran (GNU Fortran compiler, gfortran)

Execution Model

• Compiled language using gfortran (GNU Fortran compiler)
• Code is compiled to a binary, then executed
• Standard Fortran execution model with program block

Key Characteristics

• Statically typed
• Case-insensitive
• Column-based formatting (free-form in Fortran 90+)
• Requires explicit compilation step
• Uses gfortran compiler (GCC-based Fortran compiler)

Fragment Authoring

Write valid Fortran statements. Your fragment becomes the program body, so do not include program/end program. You can include use statements at the top of your fragment.

Available Modules

Standard Fortran modules are available:

• print * for formatted output
• Standard Fortran intrinsic functions
• iargc() and getarg(i, arg) for command-line arguments

Common Patterns

• Output: print *, "message"
• Variables: integer :: x = 10
• Arrays: integer, dimension(10) :: arr
• Loops: do i = 1, 10 ... end do
• Conditionals: if (condition) then ... end if
• Functions: function name(x) result(y) ... end function
• Subroutines: subroutine name(x) ... end subroutine

Examples

! Simple output
print *, "Hello from fragment!"

! Variables and calculations
integer :: a = 5
integer :: b = 10
print *, "Sum:", a + b

! Loops
integer :: i
do i = 1, 5
    print *, "Count:", i
end do

! Arrays
integer, dimension(5) :: numbers = [1, 2, 3, 4, 5]
integer :: sum = 0
integer :: i
do i = 1, 5
    sum = sum + numbers(i)
end do
print *, "Array sum:", sum

Caveats

• Fragments must be valid Fortran code that compiles
• Fortran is case-insensitive
• Use print *, for output (the * means default formatting)
• Variables must be declared before use (or use implicit typing)
• The code is compiled fresh each time, so compilation errors will fail execution
• Fortran uses 1-based array indexing by default
• String concatenation uses // operator
• Integer division truncates (use real for floating-point division)

Fraglet Scripts

Echo Args

#!/usr/bin/env -S fragletc --vein=fortran
  integer :: n, i
  character(256) :: arg
  n = iargc()
  write(*, '(a)', advance='no') 'Args:'
  do i = 1, n
    call getarg(i, arg)
    write(*, '(a)', advance='no') ' ' // trim(arg)
  end do
  print *

Stdin Upper

#!/usr/bin/env -S fragletc --vein=fortran
  character(256) :: line
  integer :: io, ci
  read(*, '(a)', iostat=io) line
  do while (io == 0)
    do ci = 1, len_trim(line)
      if (line(ci:ci) >= 'a' .and. line(ci:ci) <= 'z') line(ci:ci) = achar(iachar(line(ci:ci)) - 32)
    end do
    print *, trim(line)
    read(*, '(a)', iostat=io) line
  end do

Test

#!/usr/bin/env -S fragletc --vein=fortran
  print *, "Hello World!"

Connections

Container Info