Map vs For

[Oleg]

I will show example based on hiccup library:

For version: [:ol (for [x coll] [:li x])]
Map version: [:ol (map (fn [x] [:li x]) coll)]

What's the difference between them? What is better for performance?

Cheers, Oleg

[Moritz Ulrich]

I'd prefer the for-version in this case.

You see the differences if you try `for` and `map` with multiple collections.
`for` is a traditional list-comprehension (1).
`map` iterates over many sequences at once, `for` does "nested" iteration.

(1): http://en.wikipedia.org/wiki/List_comprehension#Clojure

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Moritz Ulrich
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[ataggart]

I prefer map for turning one sequence into another sequence of equal
length. I generally only use for when I need a cartesian product of
multiple sequences, or am going to leverage :let, :when, or :while in
the binding.