a Matryoshka doll dance
Fib.apply(
): |
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Fib.apply(
): |
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Fib.apply(
): |
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function memoize(f, args) {
// Provide default values for any missing arguments
if (args === undefined || args === null) {
args = {};
}
if (args.map === undefined || args.map === null) {
args.map = {};
}
if (args.getKey === undefined || args.getKey === null) {
args.getKey = function() {
return arguments.length > 0 ? arguments[0] : 0;
};
}
// Set the values of the utilities map and getKey
const map = args.map;
const getKey = args.getKey;
// Verify the types of the function argument and the utilities
const fType = (typeof f).toLowerCase();
const mapType = (typeof map).toLowerCase();
const getKeyType = (typeof getKey).toLowerCase();
if (fType !== 'function') {
throw Error('f is not a function');
}
if (mapType !== 'object' && mapType !== 'function') {
throw Error('invalid map type');
}
if (getKeyType !== 'function') {
throw Error('getKey is not a function');
}
// Return the memoized version of the function f
return function() {
const key = getKey.apply(this, arguments);
if (!map.hasOwnProperty(key)) {
map[key] = f.apply(f, arguments);
}
return map[key];
}
}
const Fib = new function() {
const fib = memoize(function(i) {
if (i === 1) {
return 1;
}
else if (i > 0) {
return fib(i-2) + fib(i-1);
}
else if (i < 0) {
return fib(i+2) - fib(i+1);
}
else {
return 0;
}
});
this.apply = function(n) {
const i = parseInt(n);
return i === parseFloat(n) ? fib(i) : undefined;
};
};
See also
