define('nchk(str)') :(nchk_end)
nchk    convert(str,'real') :s(return)f(freturn)
nchk_end

*       # Wrapper for testing
        define('isnum(str)') :(isnum_end)
isnum   isnum = 'F'; isnum = nchk(str) 'T'
        isnum = isnum ': ' str :(return)
isnum_end

*       # Test and display
        output = isnum('123')
        output = isnum('123.0')
        output = isnum('123.')
        output = isnum('-123')
        output = isnum('3.14159')
        output = isnum('1.2.3')
        output = isnum('abc')
        output = isnum('A440')
end