Ruby’s Enumerable module provides a couple of methods for stepping through an enumerable with the index of the element as well. However, a couple are missing — there is no inject_with_index or map_with_index. There are a couple of ways of remedying this.
First map_with_index:
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a=%w(A C C T) puts a.map.with_index {|x,index| "#{index}:#{x}"} |
You could also monkeypatch.
Unfortunately, inject.with_index won’t work without monkeypatching the module — inject takes either a symbol representing a method or a block. However, you can do:
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# Count differences between the two a=%w(A C C T) b=%w(A C C G) differences = a.each_with_index.inject(0) do |s,(c,pos)| s += (c != b[pos]) ? 1 : 0 end |
The ruby forum had an interesting thread about this with comparing the cost between “elegant/maintainable” code and faster — chaining enumerable methods (at least at the time — 2011) increased the cost of execution.
