Path: utzoo!mnetor!uunet!actnyc!jhs
From: jhs@actnyc.UUCP (John Spicer)
Newsgroups: comp.lang.fortran
Subject: Re: Recursion
Message-ID: <748@actnyc.UUCP>
Date: 25 Mar 88 16:31:44 GMT
References: <7975@agate.BERKELEY.EDU> <533@a.UUCP> <534@a.UUCP>
Distribution: na
Organization: InterACT Corporation, New York
Lines: 27
Summary: RECURSIVE keyword is useful

It has been pointed out that FORTRAN can support recursion as the language
now exists.  This is true, as is proven by the number of implementations that
support recursion.  However, this does not mean that a recursive keyword is
not useful.

1. Many FORTRAN compilers allocate variables as if the were SAVED'd to conform
   to common practice that expects this to be true.  A recursive keyword allows
   a compiler to continue to do this for non-recursive subprograms.

2. Some architechtures do not support recursion well.  For example, on the
   IBM 370 architechture, it is common to have static parameter packs for
   subroutine calls, and other static structures.  On these systems, the
   static approach is usually more efficient than building the structures
   dynamically.  Non-recursive procedures could continue to use the more
   efficient system.

3. Many FORTRAN implementations use dope-vectors for adjustable bound arrays.
   Recursive routines must construct the dope vector dynamically.
   Non-recursive routines can build most of the dope vectory statically.

The recursive keyword is useful because it allows each implementation to
make choices based on a given architechtures, and not produce slower code
just because a given subprogram may end up being called recursively.

John Spicer
InterACT Corp.
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