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Async IO Monad for Javascript
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var body = forever $do { | |
a <- readN(6) | |
b <- read1 | |
write([a, b]) | |
}; | |
performWith(ls)(body); |
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// a sweet.js macro for a subset of haskell style do-notation | |
macro $do { | |
rule { { $y:expr } } => { | |
$y | |
} | |
rule { { $x:ident <- $y:expr $rest ... } } => { | |
($y.chain(function($x) { | |
return $do { $rest ... } | |
})); | |
} | |
} |
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function IO(unsafePerform) { | |
this.unsafePerform = unsafePerform; | |
} | |
IO.prototype.of = IO.of = function (v) { | |
return new IO(function (ctx, cb) { | |
cb(null, v); | |
}); | |
}; | |
IO.prototype.empty = IO.empty = function () { | |
return IO.fail(null); | |
}; | |
IO.fail = function (message) { | |
return new IO(function (ctx, cb) { | |
cb(new Error(message)); | |
}); | |
}; | |
IO.prototype.handleError = function (f) { | |
var io = this; | |
return new IO(function (ctx, cb) { | |
io.unsafePerform(ctx, function (err, v) { | |
if (err != null) { f(err, cb); } | |
else { cb(null, v); } | |
}); | |
}); | |
}; | |
IO.prototype.chain = function (f) { | |
var io = this; | |
return new IO(function (ctx, cb) { | |
io.unsafePerform(ctx, function (e, v) { | |
if (e != null) { | |
cb(e); | |
} else { | |
f(v).unsafePerform(ctx, cb); | |
} | |
}); | |
}); | |
}; | |
IO.prototype.map = function (f) { | |
return this.chain(function (v) { | |
return IO.of(f(v)); | |
}); | |
}; | |
IO.prototype.ap = function (io) { | |
return this.chain(function (f) { | |
return io.map(f); | |
}); | |
}; | |
function write() { | |
var args = arguments; | |
return new IO(function (stream, cb) { | |
stream.write(args); | |
cb(null, null); | |
}); | |
} | |
var read1 = new IO(function (stream, cb) { | |
stream.read(cb); | |
}); | |
function liftM2(f) { | |
return function (a, b) { | |
return a.chain(function (x) { | |
return b.map(function (y) { | |
return f(x, y); | |
}); | |
}); | |
}; | |
} | |
var cons = liftM2(function (a, b) { | |
return [a].concat(b); | |
}); | |
function readN(n) { | |
return n === 0 ? IO.of([]) | |
: cons(read1, readN(n - 1)); | |
} | |
function perform(ls) { | |
return function (io) { | |
io.unsafePerform(ls, function (e, v) { | |
if (e != null) { | |
throw e; | |
} | |
}); | |
}; | |
} | |
function forever(f) { | |
return $do { | |
_ <- f() | |
forever(f) | |
}; | |
} |
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write: [ [ 0, 1, 2, 3, 4, 5 ], 6 ] | |
write: [ [ 7, 8, 9, 10, 11, 12 ], 13 ] | |
write: [ [ 14, 15, 16, 17, 18, 19 ], 20 ] | |
write: [ [ 21, 22, 23, 24, 25, 26 ], 27 ] | |
write: [ [ 28, 29, 30, 31, 32, 33 ], 34 ] | |
write: [ [ 35, 36, 37, 38, 39, 40 ], 41 ] | |
write: [ [ 42, 43, 44, 45, 46, 47 ], 48 ] | |
write: [ [ 49, 50, 51, 52, 53, 54 ], 55 ] | |
write: [ [ 56, 57, 58, 59, 60, 61 ], 62 ] | |
write: [ [ 63, 64, 65, 66, 67, 68 ], 69 ] | |
write: [ [ 70, 71, 72, 73, 74, 75 ], 76 ] | |
write: [ [ 77, 78, 79, 80, 81, 82 ], 83 ] | |
write: [ [ 84, 85, 86, 87, 88, 89 ], 90 ] |
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