Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site crystal.UUCP
Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!linus!philabs!cmcl2!seismo!uwvax!crystal!shekita
From: shekita@crystal.UUCP
Newsgroups: net.lang.c
Subject: more questions about efficient C code
Message-ID: <474@crystal.UUCP>
Date: Fri, 21-Jun-85 14:18:14 EDT
Article-I.D.: crystal.474
Posted: Fri Jun 21 14:18:14 1985
Date-Received: Mon, 24-Jun-85 04:48:43 EDT
Distribution: net
Organization: U of Wisconsin CS Dept
Lines: 35

I am currently modifying C code, written by someone else,
that is incredibly terse. It's paramount that the code
be fast, so I presume the code is terse for speed. I'm
now curious about a few things:

1) Is the "var = (bool expr) ? : expr1 : expr2" construct faster
   than just a good old if statement? 

2) Are for loops faster than while loops? 

3) Is there really much to be gained by using assignment within
   a boolean expression, for example, is

	if ((fp = fopen("foo", "r") == NULL) {
		 ...
	}

   really that much faster than

	fp = fopen("foo", "r");
	if (fp == NULL) {
		...
	}

 4) Are tests for zero more efficently written as

	if (var) {
		...
	}

    rather than as

	if (var != 0) {
		...
	}