Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!softrue!kearns
From: kearns@softrue.UUCP (Steven Kearns)
Newsgroups: comp.lang.c++
Subject: simplifying C++
Message-ID: <5.UUL1.3#8618@softrue.UUCP>
Date: 20 Feb 91 05:37:04 GMT
Organization: Software Truth
Lines: 37


Here is another in the continuing series:  "Simplifying C++".  

Expression languages are languages where each statement returns a value.
Lets make C++ an expression language as follows:

	Expression Statements, like "a = 5;", return the value of the 
		expression.
	"if (e1) s1; else s2;" returns the value of s1 if e1 true, otherwise
		it returns the value of s2.  If s1 and s2 
		return values of different types, the "if" returns a void.
	"{s1; s2; s3;} returns the value of the last statement in the
		compound statement. 
	All other statements, including an if statement without an else,
		return void.

The advantage of this is manyfold: first, we get to eliminate the
comma operator, which is used to evaluate multiple expressions as in
(e1, e2, e3).  Instead, you can write {e1; e2; e3;}.  Also, we can
eliminate the ugly (B ? e1 : e2) syntax, writing (if (B) e1; else e2;) 
instead.

Also, you can do things impossible before, for example declaring
variables inside expressions:

	if {int i = f(a, b); i >=3 && i <= 33;}
		cout << "hi there";

We probably want to disallow "gotos" and "returns" inside a compound
statement used as an expression.  

-steve

********************************************************
* Steven Kearns            ....uunet!softrue!kearns    *
* Software Truth           softrue!kearns@uunet.uu.net *
********************************************************