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DrBoolean/rep9.js

Created July 20, 2017 20:32
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rep9
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rep9.js
const Reader = f =>
({
 run: f,
 map: g => Reader(x => g(f(x))),
 chain: g => Reader(x => g(f(x)).run(x))
})
Reader.of = x => Reader(() => x)
// function application
Reader(x => x + 1).run(2) // 3
// map is just function composition
Reader(x => ‘hello ${x}’)
.map(x => x.toUpperCase())
.run(‘world’) // HELLO WORLD
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