On Sunday, 14 April 2013 at 23:54:57 UTC, bearophile wrote:
Idan Arye:
(because it's a useful function)
I think you should explain why you think it's useful.
Bye,
bearophile
Well, `predSwitch` has two main advantages on regular `switch`.
The first is being able to choose your own predicate. `switch` is
preferable to a chain of `if`-`else if` because it's a clearer
syntax(and because of the usage of lookup tables, but
`predSwitch` does not have that), but not all `if`-`else if`
chains are about simple equality checking - sometimes you need to
check for other things, like which collection contains a value.
Choosing your own predicate is helpful for that.
The second advantage - which I consider much more important - it
that `predSwitch` returns a value. This means you can use it
mid-expression - for example, to initialize a constant, or to
determine a function argument. You can't do those things with
`switch` because it's a statement. If you try to initialize a
constant in a `switch` statement, the constant's scope will be
limited to the `case` where it is defined, and if you want to use
`switch` to determine a function argument, you're gonna have to
write the rest of the function call in each `case`.
