问题
I'm trying to understand the difference between *(1..9) and [*1..9]
If I assign them to variables they work the same way
splat1 = *(1..9) # splat1 = [1, 2, 3, 4, 5, 6, 7, 8, 9]
splat2 = [*1..9] # splat2 = [1, 2, 3, 4, 5, 6, 7, 8, 9]
But things get weird when I try to use *(1..9) and [*1..9] directly.
*(1..9).map{|a| a.to_s} # syntax error, unexpected '\n', expecting tCOLON2 or '[' or '.'
[*1..9].map{|a| a.to_s} # ["1", "2", "3"...]
I'm guessing part of the problem is with operator precidence? But I'm not exactly sure what's going on. Why am I unable to use *(1..9) the same I can use [*1..9]?
回答1:
I believe the problem is that splat can only be used as an lvalue, that is it has to be received by something.
So your example of *(1..9).map fails because there is no recipient to the splat, but the [*1..9].map works because the array that you are creating is the recipient of the splat.
UPDATE: Some more information on this thread (especially the last comment): Where is it legal to use ruby splat operator?
来源：https://stackoverflow.com/questions/7557382/understanding-ruby-splat-in-ranges-and-arrays