Split lib.ts into layout.ts and util.ts

1 files changed, 88 insertions, 0 deletions

diff --git a/src/util.ts b/src/util.ts
new file mode 100644
index 0000000..79c2b5c
--- /dev/null
+++ b/src/util.ts
@@ -0,0 +1,88 @@
+/*
+ * Contains commonly-used utility functions.
+ */
+
+// Returns [0 ... len]
+export function range(len: number){
+	return [...Array(len).keys()];
+}
+// Returns sum of array values
+export function arraySum(array: 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){
+	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], then null
+export function updateAscSeq(seq: number[], maxLen: number){
+	// 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;
+}