tone/build/esm/event/PatternGenerator.js

A Web Audio framework for making interactive music in the browser.

import { assert } from "../core/util/Debug.js";
import { clamp } from "../core/util/Math.js";
/**
 * Start at the first value and go up to the last
 */
function* upPatternGen(numValues) {
    let index = 0;
    while (index < numValues) {
        index = clamp(index, 0, numValues - 1);
        yield index;
        index++;
    }
}
/**
 * Start at the last value and go down to 0
 */
function* downPatternGen(numValues) {
    let index = numValues - 1;
    while (index >= 0) {
        index = clamp(index, 0, numValues - 1);
        yield index;
        index--;
    }
}
/**
 * Infinitely yield the generator
 */
function* infiniteGen(numValues, gen) {
    while (true) {
        yield* gen(numValues);
    }
}
/**
 * Alternate between two generators
 */
function* alternatingGenerator(numValues, directionUp) {
    let index = directionUp ? 0 : numValues - 1;
    while (true) {
        index = clamp(index, 0, numValues - 1);
        yield index;
        if (directionUp) {
            index++;
            if (index >= numValues - 1) {
                directionUp = false;
            }
        }
        else {
            index--;
            if (index <= 0) {
                directionUp = true;
            }
        }
    }
}
/**
 * Starting from the bottom move up 2, down 1
 */
function* jumpUp(numValues) {
    let index = 0;
    let stepIndex = 0;
    while (index < numValues) {
        index = clamp(index, 0, numValues - 1);
        yield index;
        stepIndex++;
        index += stepIndex % 2 ? 2 : -1;
    }
}
/**
 * Starting from the top move down 2, up 1
 */
function* jumpDown(numValues) {
    let index = numValues - 1;
    let stepIndex = 0;
    while (index >= 0) {
        index = clamp(index, 0, numValues - 1);
        yield index;
        stepIndex++;
        index += stepIndex % 2 ? -2 : 1;
    }
}
/**
 * Choose a random index each time
 */
function* randomGen(numValues) {
    while (true) {
        const randomIndex = Math.floor(Math.random() * numValues);
        yield randomIndex;
    }
}
/**
 * Randomly go through all of the values once before choosing a new random order
 */
function* randomOnce(numValues) {
    // create an array of indices
    const copy = [];
    for (let i = 0; i < numValues; i++) {
        copy.push(i);
    }
    while (copy.length > 0) {
        // random choose an index, and then remove it so it's not chosen again
        const randVal = copy.splice(Math.floor(copy.length * Math.random()), 1);
        const index = clamp(randVal[0], 0, numValues - 1);
        yield index;
    }
}
/**
 * Randomly choose to walk up or down 1 index
 */
function* randomWalk(numValues) {
    // randomly choose a starting index
    let index = Math.floor(Math.random() * numValues);
    while (true) {
        if (index === 0) {
            index++; // at bottom, so force upward step
        }
        else if (index === numValues - 1) {
            index--; // at top, so force downward step
        }
        else if (Math.random() < 0.5) {
            // else choose random downward or upward step
            index--;
        }
        else {
            index++;
        }
        yield index;
    }
}
/**
 * PatternGenerator returns a generator which will yield numbers between 0 and numValues
 * according to the passed in pattern that can be used as indexes into an array of size numValues.
 * @param numValues The size of the array to emit indexes for
 * @param pattern The name of the pattern use when iterating over
 * @param index Where to start in the offset of the values array
 */
export function* PatternGenerator(numValues, pattern = "up", index = 0) {
    // safeguards
    assert(numValues >= 1, "The number of values must be at least one");
    switch (pattern) {
        case "up":
            yield* infiniteGen(numValues, upPatternGen);
        case "down":
            yield* infiniteGen(numValues, downPatternGen);
        case "upDown":
            yield* alternatingGenerator(numValues, true);
        case "downUp":
            yield* alternatingGenerator(numValues, false);
        case "alternateUp":
            yield* infiniteGen(numValues, jumpUp);
        case "alternateDown":
            yield* infiniteGen(numValues, jumpDown);
        case "random":
            yield* randomGen(numValues);
        case "randomOnce":
            yield* infiniteGen(numValues, randomOnce);
        case "randomWalk":
            yield* randomWalk(numValues);
    }
}
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