Technical Ramblings

Logical and Precedence

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crschmidt

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Something I was previously unaware of:

The reason for the two different variations of “and” and “or” operators is that they operate at different precedences.

PHP’s && vs. and have different precedence? Who thought this was a smart idea? What end or purpose could it possibly serve?

Yet another one of the things that just makes me smack my head. It does explain a few things — why I couldn’t do variable setting as I might in Perl, a la:

$var = $test || $default;

In this case, the test occurs first, setting $var = 1; Had I used:

$var = $test or $default;

All would have been fine.

How can someone think this is sane?

Comments

One response to “Logical and Precedence”

  1. Timwi Avatar
    Timwi

    Now I’m somewhat surprised about this. As much as I hate disagreeing with an anti-PHP statement, but:

    • I can’t believe you would want for “$var = $test || $default;” to do the assignment first. That runs contrary to intuitive expectation as well as C/C++/C#/Java/everything else.
    • I’m surprised you ask “Who thought this was a smart idea?” when the answer is probably Larry Wall. The “two AND/OR operators with different precendence” idea comes from Perl, and PHP has copied it. PHP may have messed up other precedences (I wouldn’t be surprised), but the statement that = has a higher precendence than or but a lower precendence than || applies both to PHP and to Perl.

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