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From: egnilges@phoenix.Princeton.EDU (Ed Nilges)
Newsgroups: comp.software-eng
Subject: Re: Counting semicolons (was: Re: WANTED: "C" code line counter program)
Message-ID: <7547@idunno.Princeton.EDU>
Date: 26 Mar 91 18:52:23 GMT
References: <RICHARD.91Mar12184440@dompap.iesd.auc.dk> <1991Mar15.132757.6883@comm.wang.com> <4196@zaphod.UUCP>
Sender: news@idunno.Princeton.EDU
Organization: Princeton University
Lines: 59

In article <4196@zaphod.UUCP> bobd@zaphod.UUCP (Bob Dalgleish) writes:
>Define your accuracy requirements!
>
>Some C statements don't show up as such because they are primarily
>expressions and show up in expression lists:

Good point, Bob.  A strict metric using "statement" as defined in the
Backus-Naur Form definition of C would measure the following code
fragment


     index = 0;
     count = 0;
     for ( ; index<limit; index++ ) if ( condition ) count++;


as "larger" than                     


     for ( index = 0, count = 0; index<limit; index++ )
         if ( condition ) count++;


The first example contains five "BNF statements":


     1.  index = 0;
     2.  count = 0;
     3.  for ( clause ) ...
     4.  if ...
     5.  count++



while the second example contains three.  

Apart from showing the ultimate folly of "measuring complexity", this
shows that the metric based on BNF statements can be refined although
it is vastly superior to line counts.  Since in C assignment is an
operator, perhaps a separate count of all expressions that use
assignment should be provided.  But you cannot escape the "complexity"
of BNF.

>Prescription: choose something that is easy to count with a standard
>Unix tool: i.e., wc, grep, sed, etc.  Then, determine how accurate it is
>for the sample code that you are using - within 5%, within 2.5%,
>whatever.  Is this good enough for your usage?

Within 5 percent of what?  What's your independent measure of
complexity?

And note that yacc and lexx are also standard unix tools.

>Don't get bogged down in what is a statement, or other metaphysical
>things.  Just find something that is well correlated with your needs,
>and measure it cheaply.  Anything else misses the point.

There is nothing "metaphysical" about using the right tool for the
job.  Unless "metaphysical"=="I don't understand it".