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Mention postfix and prefix on increment / decrement guide
Please complete the information below:
Where is the problem?
Incrementing / Decrementing guide.
What is the problem?
We never talk of the consequences of a post- or pre-increment/decrement.
If Hack is someone's first language (maybe one day), they should also learn what this means conceptually.
Please don't change anything below this point.
- Build ID: HHVM=HHVM-4.154.0:HSL=v4.108.1:2022-05-16T17:51:53+0000:1fa47f258c6b68f8ec01899aa82fd6ffa0957109
- Page requested: /hack/expressions-and-operators/incrementing-and-decrementing
- Page requested at: Wed, 18 May 2022 21:13:52 +0000
- Controller: GuidePageController
As I understand it, there is no significant difference in Hack: in other languages, it matters when it is used in an expression, but ++$x and $x++ are both statements in Hack, not expressions, so the difference can't come up in valid hack code:
$x = 123;
var_dump($x++); // Parsing[1002] Assignments can no longer be used as expressions.
var_dump(++$x); // Parsing[1002] Assignments can no longer be used as expressions.
@fredemmott
I ran some test code and I think it makes a difference with this specific example, but I can't think of any other reason why since you can't use them for assignments to other variables or such.
@EvanHelstrom the runtime still understands it (it wasn't always banned), but as the typechecker bans it, it's not considered valid Hack code - especially as it's 1002 'parse error', which no projects should permit HH_FIXMEs for.
I guess we can just close this issue then since there isn't really a need for it to be adjusted. Or should it be explained with no use case?
If there's no real consequence in Hack and you think readers will know ++ and -- by proxy of other languages, I'm fine with you closing this issue.
Per discussion above, there's no significant difference as this syntax is only allowed in statements.
