Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!dali.cs.montana.edu!milton!seymour
From: seymour@milton.u.washington.edu (Richard Seymour)
Newsgroups: comp.lang.fortran
Subject: Re: another side effect question
Keywords: function, print
Message-ID: <5806@milton.u.washington.edu>
Date: 1 Aug 90 18:00:49 GMT
References: <968@nikhefh.nikhef.nl>
Organization: University of Washington, Seattle
Lines: 31

In article <968@nikhefh.nikhef.nl> t19@nikhefh.nikhef.nl (Geert J v Oldenborgh) writes:
>
>While on the subject of side effect of functions, is there anything in the 
>(77) standard which prohibits
>
>      PRINT *,AAP(1.)
>      END
>      REAL FUNCTION AAP(X)
>      PRINT *,'THIS IS AAP'
>      AAP = X
>      END
>
  --- yes, there is:  page 12-29, section 12.11 "Restrictions on
 Function References and List Items"
"A function must not be referenced within an expression appearing 
anywhere in an input/output statement if such a reference causes an
input/output statement to be executed."

another way to look at it is to consider the PRINT statement as a
subroutine call (sort of) -- so haveing a PRINT invoke a PRINT is
recursion, which we all know Fortran thinks is nasty (page 3-6).

>
>None of the Fortrans I use properly prints this.  Yet, I find it a useful 
>construct to remind me which set of functions I am using (of course only 
>printing on the first call).
 ... many things are useful, Fortran just doesn't let you do them
 (legally)

good luck
--dick