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From: "Nasser M. Abbasi" <nma@12000.org>
Newsgroups: comp.lang.ada
Subject: Re: getting same output as gfortran, long_float
Date: Fri, 01 May 2015 13:03:45 -0500
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Date: 2015-05-01T13:03:45-05:00
List-Id: <comp.lang.ada>

On 5/1/2015 12:27 PM, Nasser M. Abbasi wrote:
>
> Thanks. My mistake. So the command line flag was needed after all!!
>
>> gfortran -Wall -fdefault-real-8  foo2.f90
>> ./a.out
>      1.82898948331047096479195244627343369E-0003
>
> Without the flag, the digit is different
>
>> gfortran -Wall foo2.f90
>> ./a.out
>      1.82898948331047112025871115292829927E-0003
>
...
> I thought with -Wall it will catch all these things, but I think
> I need more flags to detect this user error
>

Just for completion, there is a flag that checks for this user error:

----------------------------
>gfortran -Wall -Wconversion -Wconversion-extra  foo2.f90
foo2.f90:6.4:

x = 12.0D0 * 0.0001D0/(1.0D0 * (1.0D0 - 0.1D0)**4 )
     1
Warning: Conversion from REAL(8) to REAL(16) at (1)
-------------------------------

While this gives clean compile:

gfortran -Wall -Wconversion -Wconversion-extra -fdefault-real-8  foo2.f90

So, Fortran can be made to be "stroger typed", but it I think it takes
more effort than with Ada, which would have detected such
implicit conversions at the language semantics level without
the need of a compiler switches.

--Nasser