Quirks and programming. The topic reminded me of an old C book flush with anecdotal wisdom and insight (though old by now: it predates C99). The following note is preserved there: 

From decvax!harpo!npoiv!alice!research!dmr
Date: Fri Oct 22 01:04:10 1982
Subject: Operator precedence
Newsgroups: net.lang.c

The priorities of && || vs. == etc. came about in the following way.

Early C had no separate operators for & and && or | and ||. (Got that?) Instead it used the notion (inherited from B and BCPL) of "truth-value context": where a Boolean value was expected, after "if" and "while" and so forth, the & and | operators were interpreted as && and || are now; in ordinary expressions, the bitwise interpretations were used. It worked out pretty well, but was hard to explain. (There was the notion of "top-level operators" in a truth-value context.)

The precedence of & and | were as they are now. Primarily at the urging of Alan Snyder, the && and || operators were added. This successfully separated the concepts of bitwise operations and short-circuit Boolean evaluation. However, I had cold feet about the precedence problems. For example, there were lots of programs with things like

	if (a==b & c==d) ...

In retrospect it would have been better to go ahead and change the precedence of & to higher than ==, but it seemed safer just to split & and && without moving & past an existing operator. (After all, we had several hundred kilobytes of source code, and maybe 3 installations....)

Dennis Ritchie

So, yes, the short-circuiting behavior was part of C from very beginning, even before logical && || were introduced. (And the explanation why bitwise operators have the wrong precedence in C and most other C-like languages.)

In reply to Re^10: next unless condition by oiskuu
in thread next unless condition by hankcoder

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.