Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!udel!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: evaluating math w/o recompile
Message-ID: <11068@smoke.BRL.MIL>
Date: 14 Sep 89 21:31:05 GMT
References: <7598@goofy.megatest.UUCP> <34566@apple.Apple.COM> <556@tigger.planet.bt.co.uk> <451@siswat.UUCP> <72603@yale-celray.yale.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 16

In article <72603@yale-celray.yale.UUCP> zador-anthony@CS.YALE.EDU (anthony zador) writes:
>I would like to be able to specify the form of the function f
>at *run time* (no recompiles). That is, i would like 
>to place a line of math
>in some file and have the program read it in and evaluate it.
>I have played around with "hoc", the high order calculator
>described in the Unix Programming Environment by K&P, but that seems
>like overkill for this task. Is there a simpler way?

Because C expressions have to be compiled (in most C environments, anyway),
there's no way to input C language pieces at run time.  You could however
construct a source file, invoke the compiler on it, and execute it to
get the results (into a file or via IPC), assuming a decent operating
system environment.  The portable way to do this is to build a language
translator/interpretor into your application, much along the lines of
the code used in "hoc".