map, filter, reduce in Julia

The functional trio, plus transforms built into the folds.

exposures = [120, 300, 90, 240, 60]

# map transforms, filter keeps, reduce folds.
minutes = map(s -> s / 60, exposures)
println(minutes)

long_subs = filter(s -> s >= 120, exposures)
println("Long subs: $long_subs")

total = reduce(+, exposures)
println("Total: $total s")

# sum, maximum and friends take a transform as first argument.
println("In minutes: ", sum(s -> s / 60, exposures))
println("Longest: ", maximum(exposures), " s")

How it works

1. map and filter take the function first.
2. reduce(+, xs) folds with any binary operation.
3. sum(f, xs) and maximum(xs) fold and transform in one call.

The run, in numbers

Lines

15

Characters to type

437

Tokens

98

Three-star pace

70 tpm

At the three-star pace of 70 tokens a minute, this run takes about 84 seconds.

Type this snippet

Step 2 of 3 in Broadcasting, step 14 of 27 in Language basics.

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map, filter, reduce in other languages

• Swift