From 19f7dc165774dc7521436816aaf8a9eec2ac75f1 Mon Sep 17 00:00:00 2001
From: alex <alex@slab.org>
Date: Fri, 15 Apr 2022 15:05:30 +0100
Subject: [PATCH] add brand (boolean rand) and brandBy

---
 packages/core/signal.mjs | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/packages/core/signal.mjs b/packages/core/signal.mjs
index e8c66171..29a925f6 100644
--- a/packages/core/signal.mjs
+++ b/packages/core/signal.mjs
@@ -29,23 +29,22 @@ export const square2 = square._toBipolar();
 export const tri = fastcat(isaw, saw);
 export const tri2 = fastcat(isaw2, saw2);
 
-
 // random signals
 
-const xorwise = x => {
-  const a = (x << 13) ^ x
-  const b = (a >> 17) ^ a
-  return (b << 5) ^ b
-}
+const xorwise = (x) => {
+  const a = (x << 13) ^ x;
+  const b = (a >> 17) ^ a;
+  return (b << 5) ^ b;
+};
 
 // stretch 300 cycles over the range of [0,2**29 == 536870912) then apply the xorshift algorithm
-const _frac = x => x - Math.trunc(x);
+const _frac = (x) => x - Math.trunc(x);
 
-const timeToIntSeed = x => xorwise(Math.trunc(_frac(x / 300) * 536870912));
+const timeToIntSeed = (x) => xorwise(Math.trunc(_frac(x / 300) * 536870912));
 
-const intSeedToRand = x => (x % 536870912) / 536870912;
+const intSeedToRand = (x) => (x % 536870912) / 536870912;
 
-const timeToRand = x => intSeedToRand(timeToIntSeed(x));
+const timeToRand = (x) => intSeedToRand(timeToIntSeed(x));
 
 const timeToRandsPrime = (seed, n) => {
   const result = [];
@@ -53,9 +52,13 @@ const timeToRandsPrime = (seed, n) => {
     result.push(intSeedToRand(seed));
     seed = xorwise(seed);
   }
-  return(result);
-}
+  return result;
+};
 
-const timeToRands = (t, n) => timeToRandsPrime(timeToIntSeed(t), n)
+const timeToRands = (t, n) => timeToRandsPrime(timeToIntSeed(t), n);
 
-export const rand = signal(timeToRand)
+export const rand = signal(timeToRand);
+
+export const _brandBy = (p) => rand.fmap((x) => x < p);
+export const brandBy = (pPat) => reify(pPat).fmap(_brandBy).innerJoin();
+export const brand = _brandBy(0.5);