Monkey オライリー

P209の試運転

>> let map = fn(arr, f) {let iter = fn(arr, accumulated) {if (len(arr) == 0) {accumulated} else {iter(rest(arr), push(accumulated, f(first(arr))));}};iter(arr, []);};
>> let a = [1, 2, 3, 4];
>> let double = fn(x) { x * 2 };
>>  map(a, double);
[2, 4, 6, 8]

>> let reduce = fn(arr, initial, f) { let iter = fn(arr, result) { if (len(arr) == 0) { result } else { iter(rest(arr), f(result, first(arr))); } }; iter(arr, initial); };
>> let sum = fn(arr) {reduce(arr, 0, fn(initial, el) { initial + el });};
>>  sum([1, 2, 3, 4, 5]);
15

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