Comments on: Does Scala have Java’s ternary operator?

By: jherber

jherber — Fri, 07 Nov 2008 04:59:12 +0000

anyone else care for the look of R’s ifelse function?

def ifelse[U](c:Boolean, t_exp: =>U, f_exp: =>U) = if (c) t_exp else f_exp

val x = ifelse(condition, “true”, “false”) // no parenthesis corner cases
val x = condition ? “true” | “false”

unfortunately, scala doesn’t infer the type on the partial

val t = ifelse( _:Boolean, b, c)

By: Tony Morris

Tony Morris — Wed, 29 Oct 2008 20:15:06 +0000

Pawel, Yes it is needed. Not because of the terser syntax (I happen to prefer it though), but because it allows composition of the smaller parts.

e.g.
val t = _ ? b | c is a function that takes a boolean and returns the least common superclass of b and c. In other words ‘if’ should be a regular function (which the compiler optimises), not a language specialty. The bad habit here, is copying older languages without call-by-name semantics by making it a language feature.

By: Pawel Badenski

Pawel Badenski — Wed, 29 Oct 2008 09:37:18 +0000

And the big question is “do we really need it ?”. “if a else b” is a nice Scala idiom, and in my opinion introducing “a ? b | c” is just bringing old habits to a new environment. It doesn’t really hurt in this case but I can resist the feeling it’s some sort of a bad smell…

By: Erkki Lindpere

Erkki Lindpere — Mon, 13 Oct 2008 22:27:23 +0000

Nice, why didn’t I think of that?

By: Ricky Clarkson

Ricky Clarkson — Mon, 13 Oct 2008 09:08:58 +0000

Note that the operator precedence does not match Java’s, so you’ll have to parenthesise most calls to this.