What does the multiplication symbol :* do?
enumerable, ruby, ruby-1.9
Solution
`inject()` can take a block or a symbol, but `map()` always takes a block. I think your working `map()` is concise enough.
`:*` is the symbol name for the multiplication method.
Update: I think your working `map()` is fine, but it seems like what you might be looking for is the classic map/reduce, even though it's actually longer:
[[1,2], [3,4], [5,6]].map{|a| a.reduce(:*)}
Problem
In particular, using inject, the following scripts, - `puts (1..5).inject {|x, y| x * y}` and - `puts (1..5).inject(:*)`, both have output `120` as I expected. However, the script ``` print [[1,2], [3,4], [5,6]].map {|x, y| x * y} ``` has output ``` [2, 12, 30] ``` as expected but the script ``` print [[1,2], [3,4], [5,6]].map(:*) ``` raises an `ArgumentError`: ``` confused_ruby_map_inject.rb:1:in `map': wrong number of arguments(1 for 0) (ArgumentError) from confused_ruby_map_inject.rb:1:in `<main>' ``` Why is this happening, what does `:*` do, and what's the most concise way to achieve the result I'm looking for with the second set of scripts?