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September 16, 2016 09:29
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eventually correct implementation of IO Monad in JS
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| class IO extends Monad { | |
| constructor(fn) { | |
| super(); | |
| this.__value = fn; | |
| } | |
| static of(fn) { | |
| const io = new IO(() => fn); | |
| Object.freeze(io); | |
| return io; | |
| } | |
| map(f) { | |
| return new IO(compose(this.__value, f)); | |
| } | |
| mapP(res, rej) { | |
| return this.map(then(res, rej)); | |
| } | |
| flatMap(f) { | |
| /* | |
| return new IO(() => { | |
| const r = this.map(f).performIO().performIO(); | |
| return r; | |
| }); | |
| */ | |
| // same result as above. So what would be better? | |
| return this.map(f).performIO(); | |
| } | |
| join() { | |
| return this.__value; | |
| } | |
| performIO() { | |
| return this.__value(); | |
| } | |
| } |
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