From e3716be01e57e5a4eec591d606917c1bf1066b05 Mon Sep 17 00:00:00 2001
From: sanine <sanine.not@pm.me>
Date: Fri, 10 Nov 2023 12:06:35 -0600
Subject: implement hearing

---
 src/simulation/senses.js | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

(limited to 'src/simulation/senses.js')

diff --git a/src/simulation/senses.js b/src/simulation/senses.js
index 4fc96d6..0a882c9 100644
--- a/src/simulation/senses.js
+++ b/src/simulation/senses.js
@@ -3,7 +3,7 @@
 
 const frozen = {
   size: 1,
-  read: (lattice, agent) => {
+  read: (world, agent) => {
     if (agent.flags.frozen === true) {
       return [ 1 ];
     } else {
@@ -13,6 +13,39 @@ const frozen = {
 };
 
 
+// add two arrays together element-wise with a scaling factor
+function array_scalesum(a, s, b) {
+  return a.map((x, i) => x + (s*b[i]));
+}
+// determine the square of the distance between two cells
+function lattice_dist2(x0, y0, x1, y1) {
+  if (x0 === x1 && y0 === y1) { return 1; } // not proper distance but avoids divide-by-zero errors c:
+  return ((x0-x1)**2) + ((y0-y1)**2);
+}
+const hear = {
+  size: 8,
+  read: (world, agent) => {
+    const {x, y} = agent;
+    const lattice_sounds = world.lattice
+      .map((row, cy) => row.map((cell, cx) => [ 1/lattice_dist2(x, y, cx, cy), cell ]))
+      .flat()
+      .filter(([scale, cell]) => cell.flags.emit !== undefined)
+      .reduce(
+        (acc, [scale, cell]) => array_scalesum(acc, scale, cell.flags.emit),
+        [0, 0, 0, 0, 0, 0, 0, 0]
+      );
+    const agent_sounds = world.agents
+      .filter(a => a.flags.emit !== undefined)
+      .reduce(
+        (acc, a) => array_scalesum(acc, 1/lattice_dist2(x, y, a.x, a.y), a.flags.emit),
+        [0, 0, 0, 0, 0, 0, 0, 0]
+      );
+
+    return array_scalesum(lattice_sounds, 1, agent_sounds).map(ch => Math.tanh(ch));
+  },
+};
+
+
 export const senses = [
-  frozen,
+  frozen, hear,
 ];
-- 
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