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/*
* Contains utility functions.
*/
// Returns [0 ... len]
export function range(len: number): number[] {
return [...Array(len).keys()];
}
// Returns sum of array values
export function arraySum(array: number[]): number {
return array.reduce((x,y) => x+y);
}
// Returns array copy with vals clipped to within [min,max], redistributing to compensate
// Returns null on failure
export function limitVals(arr: number[], min: number, max: number): number[] | null {
let vals = [...arr];
let clipped = new Array(vals.length).fill(false);
let owedChg = 0; // Stores total change made after clipping values
while (true){
// Clip values
for (let i = 0; i < vals.length; i++){
if (clipped[i]){
continue;
}
if (vals[i] < min){
owedChg += vals[i] - min;
vals[i] = min;
clipped[i] = true;
} else if (vals[i] > max){
owedChg += vals[i] - max;
vals[i] = max;
clipped[i] = true;
}
}
if (Math.abs(owedChg) < Number.EPSILON){
return vals;
}
// Compensate for changes made
let indicesToUpdate = (owedChg > 0) ?
range(vals.length).filter(idx => vals[idx] < max) :
range(vals.length).filter(idx => vals[idx] > min);
if (indicesToUpdate.length == 0){
return null;
}
for (let i of indicesToUpdate){
vals[i] += owedChg / indicesToUpdate.length;
}
owedChg = 0;
}
}
// Usable to iterate through possible int arrays with ascending values in the range 0 to maxLen-1, starting with [0]
// eg: With maxLen 3, updates [0] to [0,1], then to [0,2], then [0,1,2]
// Returns false when there is no next array
export function updateAscSeq(seq: number[], maxLen: number): boolean {
// Try increasing last element, then preceding elements, then extending the array
let i = seq.length - 1;
while (true){
if (i > 0 && seq[i] < (maxLen - 1) - (seq.length - 1 - i)){
seq[i]++;
return true;
} else if (i > 0){
i--;
} else {
if (seq.length < maxLen){
seq.push(0);
seq.splice(0, seq.length, ...range(seq.length));
return true;
} else {
return false;
}
}
}
}
// Given a non-empty array of non-negative weights, returns an array index chosen with weighted pseudorandomness
// Returns null if array contains all zeros
export function randWeightedChoice(weights: number[]): number | null {
let thresholds = Array(weights.length);
let sum = 0;
for (let i = 0; i < weights.length; i++){
sum += weights[i];
thresholds[i] = sum;
}
let rand = Math.random();
for (let i = 0; i < weights.length; i++){
if (rand <= thresholds[i] / sum){
return i;
}
}
return null;
}
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