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Section IEEE754: Zero vs Non - Zero¶

Adapted from: https://github.com/gjbex/Fortran-MOOC/tree/master/source_code/ieee754

Illustrates that 0.0 is equal to -0.0.¶

program zero_vs_minus_zero
    implicit none
    real :: zero = 0.0, minus_zero

    minus_zero = sign(zero, -1.0)
    print '(A, 2F7.2)', '0 vs. -0: ', zero, minus_zero
    if (zero == minus_zero) then
        print '(A)', "Yes...."
        print '(A)', '0 == -0'
    else
        print '(A)', "No...."
        print '(A)', '0 /= -0'
    end if
    print '(A, F5.1)', 'sqrt(0.0) = ', sqrt(zero)
    print '(A, F5.1)', 'sqrt(-0.0) = ', sqrt(minus_zero)
end program zero_vs_minus_zero

The above program is compiled and run using Fortran Package Manager (fpm):

import os
root_dir = os.getcwd()

code_dir = root_dir + "/" + "Fortran_Code/Section_IEEE754_Zero_vs_Non_Zero"

os.chdir(code_dir)

build_status = os.system("fpm build 2>/dev/null")

fpm run output is piped into sed to suppress the status of the run command and only print the output of the executable.

exec_status = os.system("fpm run 2>/dev/null")

0 vs. -0:    0.00  -0.00
0 == -0
sqrt(0.0) =   0.0
sqrt(-0.0) =  -0.0