Elemental functions in Fortran

Write the conversion for one value; elemental maps it over arrays for free.

program elemental_functions
    implicit none
    real :: celsius(5) = [12.0, 18.5, 24.0, 31.5, 8.0]

    ! Written for one value, elemental maps it over whole arrays.
    print *, "one reading:  ", to_fahrenheit(20.0)
    print *, "all readings: ", to_fahrenheit(celsius)

contains

    elemental real function to_fahrenheit(c)
        real, intent(in) :: c
        to_fahrenheit = c * 9.0 / 5.0 + 32.0
    end function to_fahrenheit
end program elemental_functions

How it works

1. elemental real function to_fahrenheit(c) is written for a single reading.
2. Called with a scalar it returns a scalar, as usual.
3. Called with celsius, the whole array converts in one expression.

Keywords and builtins used here

• contains
• elemental
• end
• function
• implicit
• intent
• none
• print
• program
• real

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Step 3 of 3 in Procedures, step 15 of 27 in Language basics.

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