add mutation_type and mutate()

3 files changed, 71 insertions, 1 deletions

diff --git a/package.json b/package.json
index d4ad737..2621654 100644
--- a/package.json
+++ b/package.json
@@ -3,7 +3,8 @@
     "jest": "^29.5.0"
   },
   "scripts": {
-    "test": "NODE_OPTIONS=--experimental-vm-modules jest"
+    "test": "NODE_OPTIONS=--experimental-vm-modules jest",
+    "wtest": "test.bat"
   },
   "type": "module"
 }
diff --git a/src/genome/genome.js b/src/genome/genome.js
new file mode 100644
index 0000000..16de162
--- /dev/null
+++ b/src/genome/genome.js
@@ -0,0 +1,49 @@
+'use strict';

+

+

+export const mutation_type = Object.freeze({

+  none: 'none',

+  source: 'source',

+  sink: 'sink',

+  weight: 'weight',

+});

+

+

+function positive(x) {

+  if (x < 0) { 

+    return 0; 

+  } else {

+    return x;

+  }

+}

+

+

+export function mutate(gene, type, value) {

+  const [ source, sink, weight ] = gene;

+

+  switch(type) {

+    case mutation_type.none:

+      return [...gene];

+

+    case mutation_type.source:

+      if (value <= 0.5) {

+        return [ positive(source-1), sink, weight ];

+      } else {

+        return [ source+1, sink, weight ];

+      }

+

+    case mutation_type.sink:

+      if (value <= 0.5) {

+        return [ source, positive(sink-1), weight ];

+      } else {

+        return [ source, sink+1, weight ];

+      }

+

+    case mutation_type.weight:

+      const w = (8*value) - 4;

+      return [ source, sink, w ];

+

+    default:

+      throw new Error(`unknown mutation type: '${type}'`);

+  };

+}

diff --git a/src/genome/genome.test.js b/src/genome/genome.test.js
new file mode 100644
index 0000000..853d103
--- /dev/null
+++ b/src/genome/genome.test.js
@@ -0,0 +1,20 @@
+'use strict';

+

+import { mutation_type, mutate } from './genome';

+

+

+test('basic gene mutations', () => {

+  expect(mutate([0, 1, 2], mutation_type.none, 0)).toEqual([0, 1, 2]);

+

+  expect(mutate([0, 1, 2], mutation_type.source, 0.2)).toEqual([0, 1, 2]);

+  expect(mutate([1, 1, 2], mutation_type.source, 0.2)).toEqual([0, 1, 2]);

+  expect(mutate([0, 1, 2], mutation_type.source, 0.8)).toEqual([1, 1, 2]);

+

+  expect(mutate([0, 1, 2], mutation_type.sink, 0.2)).toEqual([0, 0, 2]);

+  expect(mutate([0, 1, 2], mutation_type.sink, 0.8)).toEqual([0, 2, 2]);

+  expect(mutate([0, 0, 2], mutation_type.sink, 0.2)).toEqual([0, 0, 2]);

+

+  expect(mutate([0, 1, 2], mutation_type.weight, 0.5)).toEqual([0, 1, 0]);

+  expect(mutate([0, 1, 2], mutation_type.weight, 0.0)).toEqual([0, 1, -4]);

+  expect(mutate([0, 1, 2], mutation_type.weight, 1.0)).toEqual([0, 1, 4]);

+});