Groovy optional parentheses and dots

Question

I am learning Groovy and am pretty impressed with how it allows one to build a intelligent DSL, but I am a bit confused by the rules for when parentheses and dots are optional. Consider the following code:

Integer take(Integer x) {x}
take 3 plus 4

This works as expected and produces an output of 7 (when ran in the console), as groovy understands that last line as take(3).plus(4).

Now, println take 3 plus 4 does not work as groovy understands that as println(take).3(plus).4 which is nonsense.

Every example that I am seeing shows these sort of expression by themselves on a line, but apparently

s = take 3 plus 4

works and stores the result 7 in s. My question is, why does

println( take 3 plus 4 )

not work? Obviously, groovy will parse these sort of expressions even if they are not by themselves on a line (as shown by the assignment working). I would have thought that adding those parentheses would remove the ambiguity from the form of that line that doesn't work and that it would print out 7 as I intended.

Instead groovy gives an error 'unexpected token: 3'. As far as I can tell, groovy will not allow optional parentheses or dots inside that println, even though it doesn't seem to be ambiguous. When exactly does this sort of trick work?

Answer 1

This falls into the category of a nested method call, and in that case you cannot omit the parentheses. This is causing ambiguity and the results are unexpected, as the println method thinks you are passing it multiple parameters. You could reduce the ambiguity by using a groovy string in the println method.

println "${take 3 plus 4}"

More info: Omit Parentheses