A function is a callable computation that can be passed as a value or returned as a value. In Ruby, blocks and Proc objects provide this functional style: methods can accept transformation instructions, return procs, or do both. section 16.3 section 16.3.4
Passing and returning transformations
Mapping passes a block into a method and returns a new array: [1,3,5].map { |x| x * 5 } produces [5, 15, 25]. A method can instead return a reusable computation: multiply_by(10) returns a proc, and calling that proc with 12 performs the later transformation. section 16.3
Functions become more flexible when their arguments can be supplied incrementally.
- Partial function application supplies fewer arguments than a function's arity and returns one function accepting the remainder. section 16.3.5
- Currying turns a multi-argument function into a sequence of functions, each accepting another argument; Ruby's curry method supports both patterns. section 16.3.5
def multiply_by(m)
Proc.new { puts it * m }
end
mult = multiply_by(10)
mult.call(12)
Trace a method that captures a multiplier in a returned Proc, then call the resulting function with a later argument. section 16.3.4
