1 files changed, 36 insertions, 0 deletions
diff --git a/examples/lmath.lua b/examples/lmath.lua
new file mode 100644
index 0000000..2fd0535
--- /dev/null
+++ b/examples/lmath.lua
@@ -0,0 +1,36 @@
+local lpeg = require 'lpeg'
+
+-- Lexical Elements
+local Space = lpeg.S(" \n\t")^0
+local Number = lpeg.C(lpeg.P"-"^-1 * lpeg.R("09")^1) * Space
+local TermOp = lpeg.C(lpeg.S("+-")) * Space
+local FactorOp = lpeg.C(lpeg.S("*/")) * Space
+local Open = "(" * Space
+local Close = ")" * Space
+
+-- Auxiliary function
+function eval (v1, op, v2)
+  if (op == "+") then return v1 + v2
+  elseif (op == "-") then return v1 - v2
+  elseif (op == "*") then return v1 * v2
+  elseif (op == "/") then return v1 / v2
+  end
+end
+
+-- Grammar
+local V = lpeg.V
+G = lpeg.P{ "Exp",
+  Exp = lpeg.Cf(V"Term" * lpeg.Cg(TermOp * V"Term")^0, eval);
+  Term = lpeg.Cf(V"Factor" * lpeg.Cg(FactorOp * V"Factor")^0, eval);
+  Factor = Number / tonumber + Open * V"Exp" * Close;
+}
+
+local test
+if arg[1] then
+	local f = io.open(arg[1], 'r')
+	test = f:read '*a'
+	f:close()
+else
+	test = [[10 + 5 * 2 + 10]]
+end
+print(lpeg.match(G, test))