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April 9, 2018 22:08
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Functional programming: Fibonacci function with memoization (n=8)
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const resultCombination = cache => result => (getResult = true) => getResult ? result : cache | |
const cacheResult = ({resultCombination}) => result => n => resultCombination({...result(false), [n]: result()})(result()) | |
const memoize = ({resultCombination, cacheResult}) => cache => f => n => cache.hasOwnProperty(n) | |
? resultCombination(cache)(cache[n]) | |
: cacheResult({resultCombination})(f(cache)(n))(n) | |
const fib2 = ({resultCombination, cacheResult, memoize}) => f1Result => f => n => resultCombination(f1Result(false))(f1Result() + memoize({resultCombination, cacheResult})(f1Result(false))(f)(n - 2)()) | |
const fib = ({resultCombination, cacheResult, memoize, fib2}) => cache => n => n === 1 || n === 2 | |
? resultCombination(cache)(1) | |
: fib2({resultCombination, cacheResult, memoize})(memoize({resultCombination, cacheResult})(cache)(fib({resultCombination, cacheResult, memoize, fib2}))(n - 1))(fib({resultCombination, cacheResult, memoize, fib2}))(n) | |
console.log('THE RESULT: ' + fib({ | |
resultCombination, | |
cacheResult: ({resultCombination}) => result => n => { | |
console.log(`Caching result: f(${n})=${result()}`) | |
return cacheResult({resultCombination})(result)(n) | |
}, | |
memoize: ({resultCombination, cacheResult}) => cache => f => n => { | |
console.log(cache.hasOwnProperty(n) ? `Cache hit for n=${n}` : `Calculating value for f(${n})`) | |
return memoize({resultCombination, cacheResult})(cache)(f)(n) | |
}, | |
fib2 | |
})({})(8)(true)) | |
// Calculating value for f(7) | |
// Calculating value for f(6) | |
// Calculating value for f(5) | |
// Calculating value for f(4) | |
// Calculating value for f(3) | |
// Calculating value for f(2) | |
// Caching result: f(2)=1 | |
// Calculating value for f(1) | |
// Caching result: f(1)=1 | |
// Caching result: f(3)=2 | |
// Cache hit for n=2 | |
// Caching result: f(4)=3 | |
// Cache hit for n=3 | |
// Caching result: f(5)=5 | |
// Cache hit for n=4 | |
// Caching result: f(6)=8 | |
// Cache hit for n=5 | |
// Caching result: f(7)=13 | |
// Cache hit for n=6 | |
// THE RESULT: 21 |
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