Path: utzoo!utgpu!watmath!clyde!att!mtuxo!rolls!westmark!mole-end!mat
From: mat@mole-end.UUCP (Mark A Terribile)
Newsgroups: comp.lang.c
Subject: Re: Why is switch (ptr) illegal (or how to pointers differ from scalers)?
Summary: Constant expressions at compile time
Message-ID: <121@mole-end.UUCP>
Date: 17 Dec 88 18:20:15 GMT
References: <4347@umd5.umd.edu>
Organization: mole-end--private system.  admin: mole-end!newtnews
Lines: 25


 | NOTE do, re, mi;
 | 
 | and the pointer:
 | NOTE *scale;
 | 
 | Why can I not do:
 | 
 | 	switch (scale) {
 | 
 | 	case &do:
 | 		do_something (scale);
 | 		break;

The switch() requires *compile-time* constants, rather than link-time constants
so that the compiler can determine which of several methods (table look-up,
range-checked indexing, hashed back-checked lookup, if/then ...) it should use.

Could it be changed to always do a linear search table lookup (worst case) on
a link-time expression?  Probably.  Would it encourage bad style?  Perhaps.
Should it be done?  I don't know.
-- 

(This man's opinions are his own.)
From mole-end				Mark Terribile