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13 | export const mapIterator = (iterator, f) => ({
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14 | [Symbol.iterator] () {
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15 | return this
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16 | },
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17 |
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18 | next () {
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19 | const r = iterator.next()
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20 | return { value: r.done ? undefined : f(r.value), done: r.done }
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21 | }
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22 | })
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29 | export const createIterator = next => ({
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30 | |
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32 |
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33 | [Symbol.iterator] () {
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34 | return this
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35 | },
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36 |
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37 | next
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38 | })
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42 |
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44 |
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45 | export const iteratorFilter = (iterator, filter) => createIterator(() => {
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46 | let res
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47 | do {
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48 | res = iterator.next()
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49 | } while (!res.done && !filter(res.value))
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50 | return res
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51 | })
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52 |
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57 |
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58 | export const iteratorMap = (iterator, fmap) => createIterator(() => {
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59 | const { done, value } = iterator.next()
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60 | return { done, value: done ? undefined : fmap(value) }
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61 | })
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