From 2a03fd9a56c82a711854ae82a7e596482ee8f67b Mon Sep 17 00:00:00 2001
From: sanine <sanine.not@pm.me>
Date: Wed, 1 Jan 2025 10:11:34 -0600
Subject: initial commit

---
 example.lua | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 example.lua

(limited to 'example.lua')

diff --git a/example.lua b/example.lua
new file mode 100644
index 0000000..fd61f06
--- /dev/null
+++ b/example.lua
@@ -0,0 +1,80 @@
+local Grammar = require 'grammar'
+local GA = require 'ga'
+
+
+local production = {}
+production["<start>"]={{'<expr>'}}
+production["<expr>"]={ {'<var>'}, {'(', '<expr>', '<op>', '<expr>', ')'} }
+production["<op>"]={ {'+'}, {'-'}, {'*'}, {'/'} }
+production["<var>"]={ {'x'} }
+
+
+local grammar = Grammar.createGrammar(production)
+
+
+math.randomseed(0)
+
+
+function randomGenome()
+  local len = math.ceil(math.random() * 256)
+  local genome = {}
+  for i=1,len do
+    table.insert(genome, math.floor(256 * math.random()))
+  end
+  return genome
+end
+
+
+function randomPop()
+  local pop = {}
+  for n=1,1000 do
+    table.insert(pop, randomGenome())
+  end
+  return pop
+end
+
+function evaluate(genome)
+  local s = 'return function(x) return ' .. grammar:expand(genome) .. ' end'
+  local f = assert(loadstring(s))()
+  local target = function(x) return (x*x*x*x) + (x*x*x) + (x*x) + (x) end
+  local cost = 0
+  for n=0,100 do
+    x = (n-50)/50
+    ok, y = pcall(f, x)
+    if (not ok) or (y ~= y) then
+      cost = cost + 100
+    else
+      cost = cost + math.abs(y - target(x))
+    end
+  end
+  return -((0.0001*#s) + cost)
+end
+
+local ga = GA.createGA(randomPop(), {
+  evaluate=evaluate,
+  crossover=function(a, b)
+    local crossoverPoint = math.ceil(#a * math.random())
+    local new = {}
+    for i=1,#b do
+      table.insert(new, (i>=crossoverPoint and b[i]) or a[i])
+    end
+    return new
+  end,
+  mutate=function(a)
+    local new = {}
+    for i,v in ipairs(a) do new[i] = v end
+    local mutationPoint = math.ceil(#a * math.random())
+    new[mutationPoint] = math.floor(256 * math.random())
+    return new
+  end,
+})
+
+
+for n=1,100 do
+  print(ga:step())
+  print(grammar:expand(ga.population[ga.bestMember]))
+end
+
+-- for k,v in ipairs(ga.population) do
+--   print(k, '(', v[1], v[2], v[3], ')', evaluate(v))
+-- end
-- 
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