Control expressions are functions too

I am kind of simultaneously learning Clojure and Scala, the former through the London Clojure Dojo (come and join us) and the latter through work. It is an interesting experience but I am very glad that Clojure is part of the mix as it helps understand a lot of things that are seem strange in Scala.

In Clojure everything is essentially either a function or a sequence. It is therefore not surprising to see that an if statement works like a function.

(if false 1 2)

Evaluating the above in a Clojure REPL results in the answer 2: if is a function that evaluates its first argument returning the second parameter if the evaluation is true, the third if false.

The same is true of Scala, with the additional wrinkle that if the different clauses evaluate to different types you could be in type hell. Despite its superficial similarity to Java syntax it is in fact quite different and you can compose it just as you would any other function.

1 + (if(true) 2 else 3)

Evaluated in a Scala REPL gives the result 3.

Scala 2.8 seems much better about making everything return a value (and hence act like a function), val and for will both now return Unit, which is not useful but prevents the compiler moaning.

This kind of thing is much easier to appreciate and learn in a pure functional language than in Scala where you never really know whether something is going to operate in a functional or object-orientated way.


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