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19 lines
732 B
Markdown
19 lines
732 B
Markdown
# Mapping With An Index
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If you're mapping over a collection and you need an index for each item, you
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can reach for `map-indexed`. The `map-indexed` function can be used like so:
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```clojure
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> (def foods ["pizza" "hotdog" "chicken alfredo"])
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#'cljs.user/foods
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> (map-indexed (fn [idx item] (str idx " - " item)) foods)
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("0 - pizza" "1 - hotdog" "2 - chicken alfredo")
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```
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Alternatively, `map` can take multiple sequences, and each becomes a new argument to the mapping function. By giving an infinite sequential list of numbers starting at 0 as the first sequence, you can pretend they're indices, like so:
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```clojure
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> (map (fn [idx item] (str idx " - " item)) (range) foods)
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("0 - pizza" "1 - hotdog" "2 - chicken alfredo")
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```
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