Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rice!uw-beaver!mit-eddie!andante!alice!bs
From: bs@alice.att.com (Bjarne Stroustrup)
Newsgroups: comp.object
Subject: Re: Documenting OO Systems
Keywords: operators
Message-ID: <20147@alice.att.com>
Date: 30 Mar 91 14:17:34 GMT
References: <jls.669768656@rutabaga> <299@orbit.gtephx.UUCP> <pallas.670283269@red-dwarf>
Organization: AT&T Bell Laboratories, Murray Hill NJ
Lines: 61



pallas@eng.sun.com (Joseph Pallas) writes
 > In <jls.670218725@rutabaga> jls@rutabaga.Rational.COM (Jim Showalter)
 > writes:
 > 
 > >Okay, what is this going to do?:
 > 
 > >    int j (int y, int m, int d) {
 > >    int m_d[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
 > >    if (m<1 || m>12) return 0;
 > >    int l = !(y%4) && y&400;
 > >    if (d<1 || d>(m_d[m-1] + (m==2 && y))) return 0;
 > >    int dd = 0;
 > >    for (int i=0; i<m-1; i++) dd += m_d[i];
 > >    return dd + d + (m>2 && y);
 > >    }
 > 
 > >You should be able to tell me right off the bat--you think English sucks
 > >as a programming language, and this is DEFINITELY not written in English.
 > 
 > I can't believe I'm about to waste my time on this, but here goes:
 > 
 > int j (int year, int month, int day) {
 > int month_days[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
 > if (month<1 || month>12) return 0;
 > int leap = !(year%4) && year&400;
 > if (day<1 || day>(month_days[month-1] + (month==2 && year))) return 0;
 > int dayofmonth = 0;
 > for (int i=0; i<month-1; i++) dayofmonth += month_days[i];
 > return dayofmonth + day + (month>2 && year);
 > }
 > 
 > I've left the name of the function cryptic, but the rest is the result
 > of a simple global substitution.  It becomes immediately apparent not
 > only what the function is supposed to do, but that it contains at
 > least one error (surely you meant to check (month==2 && leap)).
 > 
 > Funny thing is, the function is still written in C.
 > 
 > Amazing, isn't it?

Actually, we discover that the function was never written in C. Note the
way variables are declared exactly where they are needed. This is C++.
Also, total lack of indentation to make the code more obscure is not
too common in the C/C++ world.

int j (int year, int month, int day)
{
	int month_days[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
	if (month<1 || month>12) return 0;

	int leap = !(year%4) && year&400;
	if (day<1 || day>(month_days[month-1] + (month==2 && year))) return 0;

	int dayofmonth = 0;
	for (int i=0; i<month-1; i++) dayofmonth += month_days[i];
	return dayofmonth + day + (month>2 && year);
}

A comment or two would also help.