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Matt - sanemat
Matt - sanemat

Reputation: 5618

What do you call the -> operator in Ruby?

  1. What do you call the -> operator as in the following?

    ->(...) do
  ...
end

  2. Aren't the following snippets equivalent?

    succ = ->(x) {x + 1}
succ = lambda {|x| x + 1}

Upvotes: 250

Views: 75910

Answers (3)

Cary Swoveland
Cary Swoveland

Reputation: 110685

->(x) { ... } is the same as lambda { |x| ... }. It creates a lambda. See Kernel#lambda A lambda is a type of proc, one that ensures the number of parameters passed to it is correct. See also Proc::new and Kernel#proc.

Upvotes: 6

avpaderno
avpaderno

Reputation: 29679

In Ruby Programming Language ("Methods, Procs, Lambdas, and Closures"), a lambda defined using -> is called lambda literal. 

succ = ->(x){ x+1 }
succ.call(2)

The code is equivalent to the following one. 

succ = lambda { |x| x + 1 }
succ.call(2)

Informally, I have heard it being called stabby lambda or stabby literal.

Upvotes: 280

Yarin
Yarin

Reputation: 183569

=> == Hash Rocket

Separates keys from values in a hash map literal.

-> == Dash Rocket

Used to define a lambda literal in Ruby 1.9.X (without args) and Ruby 2.X (with args). The examples you give (->(x) { x * 2 } & lambda { |x| x * 2 }) are in fact equivalent.

Upvotes: 143

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