Re: Avoiding the == blues

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Re^2: Avoiding the == blues by TimToady (Parson) on Dec 31, 2004 at 18:12 UTC
Yes, what's really going on here is that, while the computer treats `$a == $b` as commutative, the human brain is linguistically wired, and tends to parse such constructs asymmetrically as a topic and a predicate. And as it happens, the topic likes to be first. For similar reasons most OO programmers will choose to write: `foo.equals(0)` [download] rather than: `0.equals(foo)` [download] Despite the fact that Ruby considers 0 to be a Real Object, I suspect that even Ruby programmers will prefer the first form to the second, because that's how our brains are wired. The solution to all this in Perl 6 will be that assignment to an existing variable in boolean context will produce a warning under strictures, but assignment to a `my` declaration will not. The typical use for assignment in a boolean context is actually not the `if` statement but the `while` statement: `while $item = shift(@foo) {...}` [download] and in most cases this is probably better written as: `while my $item = shift(@foo) {...}` [download] or even better: `for @foo -> $item {...}` [download] Likewise, `if $x = long_expression() {...}` [download] can turn into `given long_expression -> $x {...}` [download] I suppose we might also allow the gcc-like workaround of putting extra parens when you want to hide the assignment from the boolean context.	[reply] [d/l] [select]
Re^3: Avoiding the == blues by Anonymous Monk on Jan 01, 2005 at 19:16 UTC
Depends on the developer. It's better to write literal comparisons (literal the noun) as "bob".equals(someVariable), when there is a chance that someVariable could be null/nil/undef. Sorta the take on the if(someLiteral == someVariable) in c, so you couldn't write things like if(0=variable) by accident. Compiler err and all...	[reply]
Re^4: Avoiding the == blues by Baz (Friar) on Jan 01, 2005 at 20:25 UTC
>>"Put the constant on the left," he repeated. "You can't assign to a constant, so it's a syntax error if you say = instead of ==." Interesting, but I have to say that with practice an alarm bell goes off when I write such conditional statement anyway. In the same way that an alarm bell woulld need to go off in order to remember to put the constant on the left.	[reply]
Re^2: Avoiding the == blues by aquarium (Curate) on Dec 31, 2004 at 14:27 UTC
i don't see your point....what is your point, about not liking it? Seriously though, I think that too many programming teachers actually teach the "$foo == 0" way, which gets ingrained in a lot of us. if you think of the equality test as a weight scale, with each variable/constant being a weight, it should make it fit better for you. you can also have some fun with short circuit logic: `if ( 5 == $foo) print "tadaa";` [download] can become `( $foo -5) && print "tadaa";` [download] so you don't use == at all the hardest line to type correctly is: stty erase ^H	[reply] [d/l] [select]