From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=0.7 required=5.0 tests=BAYES_00,INVALID_DATE, MSGID_SHORT,REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!gatech!akgua!akguc!codas!peora!petsd!cjh From: cjh@petsd.UUCP (Chris Henrich) Newsgroups: net.lang.ada Subject: Re: Procedure Parameters in Ada Message-ID: <782@petsd.UUCP> Date: Mon, 9-Jun-86 13:55:40 EDT Article-I.D.: petsd.782 Posted: Mon Jun 9 13:55:40 1986 Date-Received: Thu, 12-Jun-86 01:12:33 EDT References: <8606042209.AA23350@vrdxhq.uucp> Reply-To: cjh@petsd.UUCP (C. J. Henrich) Organization: Perkin-Elmer DSG, Tinton Falls, N.J. List-Id: [] In article <8606042209.AA23350@vrdxhq.uucp> drm1@vrdxhq.UUCP (Donn Milton) writes: >Many people seem to be unaware of a major problem entailed by >procedures as parameters. That is, when procedures are allowed >as parameters, strong type-checking becomes generally undecidable >(not just hard) UNLESS recursive mode-type declarations (a la Algol 68) >are introduced. Procedure & function parameters are part of standard Pascal. In the current ANSI/ISO standard (though not in the old book by Jensen and Wirth) a certain degree of type checking is mandated. I know of at least one compiler which provides it. It is not difficult; the routine which checks for compatibility of types may have to call itself recursively. These possibilities occur to me: (a) what ANSI/ISO mandates is not "strong" in Donn Milton's sense; (b) something in Pascal corresponds to "recursive mode-type declarations; (c) for some other reason, the theorem being cited is beside the point. It may be worth while to note that subprograms as *variables* have worse problems than subprograms as *parameters.* Regards, Chris -- Full-Name: Christopher J. Henrich UUCP: ...!hjuxa!petsd!cjh US Mail: MS 313; Concurrent Computer Corporation; 106 Apple St; Tinton Falls, NJ 07724 Phone: (201) 758-7288 Concurrent Computer Corporation is a Perkin-Elmer company.