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    driver.js gibberish.js waa.js context.js compatibility.js debug.js midi.js random.js stdlib.js index.js process.js utils.js vm.js

  • random.js

  • ¶

    Randomness

    import { isArray } from "../utils"
import { ERR_EXPECT_PATTERN } from "../vm"
const { floor } = Math
  • ¶
    Name Description Example
    @random Generate a random number between 0 and 1 ["@random", "amp", "@set"]
    @rand Alias for @random
    @srandom Generate a random number between -1 and 1 ["@srandom", "phase", "@set"]
    @srand Alias for @srandom
    @randi Generate a random integer between 0 and n [60, "@randi", "midi", "@set"]
    @pick Pick a random element from a list ["@pick", [1, 2, 3, 4]]
    @shuffle Shuffle a list "@shuffle", [1, 2, 3]
    @chance Probabilistic execution probability, "@chance", executed-if-true, executed-if-false 
    export default function random ({ random } = {}) {
  • ¶

    allow to use a custom random function

      const rnd = random || Math.random
  • ¶

    a function that generates integer random from 0 to n

      const irnd = n => floor(rnd() * n)

  const shuffle = a => {
    var j, x, i
    for (i = a.length; i; i--) {
      j = floor(random() * i)
      x = a[i - 1]
      a[i - 1] = a[j]
      a[j] = x
    }
  }

  return {
    "@random": ({ stack }) => stack.push(rnd()),
    "@rand": "@random",
    "@srandom": ({ stack }) => stack.push(rnd() * 2 - 1),
    "@srand": "@srandom",
    "@randi": ({ stack }) => stack.push(irnd(stack.pop())),
    "@pick": proc => {
      const { operations, error } = proc
      const pattern = operations.pop()
      if (!isArray(pattern)) {
        operations.push(pattern)
        error("Can't pick an element if is not an array", pattern)
      } else {
        const i = irnd(pattern.length)
        operations.push(pattern[i])
      }
    },
    "@chance": ({ stack, operations }) => {
      const prob = stack.pop()
      const pattern = operations.pop()
      if (rnd() < prob) {
  • ¶

    Skip item after

            operations.pop()
  • ¶

    Push the pattern

            operations.push(pattern)
      }
    },
    "@shuffle": ({ stack, operations, error }) => {
      const pattern = operations.pop()
      if (!isArray(pattern)) error("@shuffle", ERR_EXPECT_PATTERN, pattern)
      else operations.push(shuffle(pattern))
    }
  }
}