Earlier e-mail example:
let foo =
"positive" where ( bar > 0 ) ??
"negative" where ( bar < 0 ) ??
"zero"let foo = bar > 0 ? "positive" :
bar < 0 ? "negative" :
"zero"
See, this just makes me want to remix ternary...
let foo = (bar > 0) :: "positive" ??
(bar < 0) :: "negative" ??
"zero"
// :: is not actually legal to declare, but notionally...
infix operator :: {
associativity left
precedence 133
}
func :: <B: BooleanType, T>(lhs: B, rhs: @autoclosure () -> T?) -> T? {
guard lhs else {
return nil
}
return rhs()
}
`::` is an operator which evaluates the condition on the left and returns the right if true, or nil otherwise. You can chain `::`s together with the existing `??` operator. You can terminate the sequence with a trailing `?? value` to ensure you won't get a nil. Or you can leave off the trailing `??`, or even omit the chain of `??`s altogether if `::` by itself does what your code needs.
Actually, the main problem I see here is that `??`'s, and therefore `::`'s, precedence is too tight—it binds more tightly than the comparison operators. One solution might be to put `::` and `??` at their current high precedence, but also have `:` and `?` with the same semantics at a precedence level just above assignment...
···
--
Brent Royal-Gordon
Architechies