Created
September 22, 2011 13:09
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declarative style evaluation.js
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| /* | |
| Declarative style evaluation. | |
| Advantages | |
| order of evaluation is not important | |
| evaluation is lazy i.e. its evaluated only if required | |
| auto memorization of evaluation (only for pure fns) | |
| expressions are writed as in math, no mutable values | |
| */ | |
| Object.prototype._let = #(name, _calc) { | |
| fix self = @ | |
| @__defineGetter__(name, #{ | |
| var ret = _calc() | |
| delete @[name] // memo result | |
| @[name] = ret | |
| -> ret | |
| }) | |
| } | |
| fix _solveQuadraticEquation = #(a, b, c) { | |
| with({}) | |
| { | |
| _let('D', #{ -> b*b - 4*a*c }) | |
| _let('x1', #{ -> (-b + Math.sqrt(D)) / (2*a) }) | |
| _let('x2', #{ -> (-b - Math.sqrt(D)) / (2*a) }) | |
| if(D < 0) | |
| -> [] | |
| else if(D == 0) | |
| -> [x1] | |
| else | |
| -> [x1, x2] | |
| } | |
| } | |
| _log(_solveQuadraticEquation(1, 0, -1)) |
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