Proposal: I'd love to have versions of `require` t...

# stdlib

[Leon K]

Proposal:
I'd love to have versions of require that allow for specifying a custom Exception type to throw, instead of just throwing IllegalArgumentException

[karelpeeters]

Those are called if.

[Leon K]

if doesn't do contract-stuff. i cannot do if(foo == null) throw Foo() and smart-cast foo into non-null by that

[Leon K]

also, if isn't remotely as expressive as require

[LeoColman]

You can write your own require, with the same contracts

[LeoColman]

The thing for require is that it's specifically to check for IllegalArguments, and that's why it uses IllegalArgumentException. Other use cases are on a per-user basis

[karelpeeters]

If and exception throwing does smart cast.

[Leon K]

didn't seem to do it for me, karel ^^'

[karelpeeters]

Then you need to try again because it definitely does.

[Leon K]

i will ;D

[Leon K]

i know i could write my own require, but you could say that to any proposal here in the stdlib channel. you could write any stdlib-function yourself, but you shouldn't have to ;D This would be a great addition to the standard-library imo

[karelpeeters]

So you want something like

requireThrow(i > 0) { MyException("foo") }

instead of

if (i <= 0) throw MyException("foo")

? That's not even shorter!

[karelpeeters]

I'm not suggesting you to write your own function, I'm suggesting to just use if.

[Leon K]

i know, but Leonardo was suggesting to write my own function.
my big arguent agains if here is that it isn't as expressive, thus not as readable.
when seeing

if (verrryLongConditionThatChecksSomeData) {
  throw FooException("bar")
}

you don't immediately know that this is just validation-logic. its not bad, but it could very well be better.

being short doesn't mean readable. Expressive within a given context means readable ;D