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From: debray@sbcs.UUCP (Saumya Debray)
Newsgroups: net.lang
Subject: Re: Recursion
Message-ID: <448@sbcs.UUCP>
Date: Mon, 2-Sep-85 19:48:58 EDT
Article-I.D.: sbcs.448
Posted: Mon Sep  2 19:48:58 1985
Date-Received: Wed, 4-Sep-85 06:37:15 EDT
References: <909@oddjob.UUCP> <163@ho95e.UUCP> <367@ttrdc.UUCP> <624@mmintl.UUCP> <712@gitpyr.UUCP>
Organization: Computer Science Dept, SUNY@Stony Brook
Lines: 21

Scott Holt:
>
>     I think [compile-time checking of whether a procedure is recursive]
> would be a good idea, but wouldnt it be limited to direct recursion
> ( i.e. routine A calls A as apposed to A calls B, B calls A ). I don't
> know PL/I, but I would think including such a check for anything other
> than direct recursion would be a royal pain for a compiler writter.
> 
If we assume that a program doesn't have procedure/function variables (an
assumption that's true most of the time), then static checking of whether
or not a procedure can be recursive is straightforward, at least conceptually:
it's the transitive closure of the "can_call" relation, where "can_call(A,B)"
is true if routine A can directly call routine B.  (Of course, whether or
not routine A will _in_fact_ call routine B is undecidable.)
-- 
Saumya Debray
SUNY at Stony Brook

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