102 lines
2.2 KiB
CoffeeScript
102 lines
2.2 KiB
CoffeeScript
# Basic array comprehensions.
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nums = n * n for n in [1, 2, 3] when n % 2 isnt 0
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results = n * 2 for n in nums
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ok results.join(',') is '2,18'
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# Basic object comprehensions.
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obj = {one: 1, two: 2, three: 3}
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names = prop + '!' for prop of obj
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odds = prop + '!' for prop, value of obj when value % 2 isnt 0
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ok names.join(' ') is "one! two! three!"
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ok odds.join(' ') is "one! three!"
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# Basic range comprehensions.
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nums = i * 3 for i from 1 to 3
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negs = x for x from -20 to -5*2
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eq nums.concat(negs.slice 0, 3).join(' '), '3 6 9 -20 -19 -18'
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# With range comprehensions, you can loop in steps.
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eq "#{ x for x from 0 to 9 by 3 }", '0,3,6,9'
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eq "#{ x for x from 9 to 0 by -3 }", '9,6,3,0'
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eq "#{ x for x from 3*3 to 0*0 by 0-3 }", '9,6,3,0'
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# Multiline array comprehension with filter.
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evens = for num in [1, 2, 3, 4, 5, 6] when num % 2 is 0
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num *= -1
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num -= 2
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num * -1
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eq evens + '', '4,6,8'
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# Backward traversing.
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odds = num for num in [0, 1, 2, 3, 4, 5] by -2
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eq odds + '', '5,3,1'
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# The in operator still works, standalone.
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ok 2 of evens
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# all/from/to aren't reserved.
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all = from = to = 1
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# Nested comprehensions.
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multiLiner =
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for x from 3 to 5
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for y from 3 to 5
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[x, y]
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singleLiner =
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[x, y] for y from 3 to 5 for x from 3 to 5
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ok multiLiner.length is singleLiner.length
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ok 5 is multiLiner[2][2][1]
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ok 5 is singleLiner[2][2][1]
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# Comprehensions within parentheses.
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result = null
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store = (obj) -> result = obj
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store (x * 2 for x in [3, 2, 1])
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ok result.join(' ') is '6 4 2'
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# Closure-wrapped comprehensions that refer to the "arguments" object.
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expr = ->
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result = item * item for item in arguments
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ok expr(2, 4, 8).join(' ') is '4 16 64'
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# Fast object comprehensions over all properties, including prototypal ones.
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class Cat
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constructor: -> @name = 'Whiskers'
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breed: 'tabby'
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hair: 'cream'
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whiskers = new Cat
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own = value for key, value of whiskers
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all = value for all key, value of whiskers
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ok own.join(' ') is 'Whiskers'
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ok all.sort().join(' ') is 'Whiskers cream tabby'
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# Comprehensions safely redeclare parameters if they're not present in closest
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# scope.
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rule = (x) -> x
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learn = ->
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rule for rule in [1, 2, 3]
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ok learn().join(' ') is '1 2 3'
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ok rule(101) is 101
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