Ruby Tips & Tricks #2: Lambda Literals in 1.9.3

Ruby 1.9.3 support is coming to an end and with it — an end of a syntax limitation. Welcome to the second Ruby Tips & Tricks post.

Have you ever wondered why the community style guide suggest you to write lambda literals like ->(a, b) { a + b } instead of -> (a, b) { a + b }? Well, there is a bit more than aesthetics to it…

In Ruby 1.9.3 -> (a, b) { a + b } isn’t syntactically valid:

>> -> (a, b) { a + b }
SyntaxError: (irb):1: syntax error, unexpected tLPAREN_ARG, expecting keyword_do_LAMBDA or tLAMBEG
-> (a, b) { a + b }
    ^
    from /1.9.3-p545/bin/irb:12:in `<main>'

The fore mentioned expression is valid in Ruby 2.0.0 and above. That’s what I call a significant whitespace!

Have you ever been bitten by it? Drop me a line on twitter at @gsamokovarov.