From d3148268857e01116d5d3c99ac0a43bc6a54b13c Mon Sep 17 00:00:00 2001
From: Robin Haberkorn <robin.haberkorn@googlemail.com>
Date: Wed, 29 Dec 2010 16:26:25 +0100
Subject: initial checkin (v0.1 release)

---
 samples/exp2bf.lua | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100755 samples/exp2bf.lua

(limited to 'samples/exp2bf.lua')

diff --git a/samples/exp2bf.lua b/samples/exp2bf.lua
new file mode 100755
index 0000000..dac59d4
--- /dev/null
+++ b/samples/exp2bf.lua
@@ -0,0 +1,48 @@
+#!/usr/bin/lua
+
+require "lspipat"
+
+function EXIT(...)
+	io.stderr:write(string.format(...))
+	os.exit()
+end
+
+stack = {}
+function push(val) table.insert(stack, val) end
+function binop()
+	table.insert(stack, {
+		l = table.remove(stack),
+		type = table.remove(stack),
+		r = table.remove(stack)
+	})
+end
+
+function compile(node)
+	if type(node) ~= "table" then return string.rep("+", tonumber(node)) end
+
+	local ret = compile(node.l)..">"..compile(node.r)
+	node.type:smatch( Any("+-") % function(o) ret = ret.."[<"..o..">-]<" end
+			+ "*" * -function() ret = ">>"..ret.."[<[<+<+>>-]<[>+<-]>>-]<[-]<<" end
+			+ "/" * -function() ret = ">"..ret.."<[->->+>>+<<<[>>+>[-]<<<-]>>"..
+						  "[<<+>>-]>[-<<[<+>-]<<<+>>>>>]<<<<]>[-]>[-]<<<" end,
+			  spipat.match_anchored )
+
+	return ret
+end
+
+if #arg ~= 1 then EXIT("Invalid number of parameters\n") end
+
+space = NSpan(" ")
+pre = space * ("(" * -"exp" * space * ")" + Span("0123456789") % push)
+post = space * ( Any("+-") % push * -"exp" * -binop
+	       + Any("*/") % push * pre * -binop * -"post" ) + ""
+exp = pre * post
+
+if not arg[1]:smatch(exp * RPos(0), spipat.match_anchored) then EXIT("Invalid expression!\n") end
+
+src = compile(stack[1])..
+      "[>++++++++++<[->->+>>+<<<[>>+>[-]<<<-]>>[<<+>>-]"..
+      ">[-<<[<+>-]>>>+<]<<<<]>>>>>[<<<<<+>>>>>-]>[>]"..string.rep("+", string.byte("0"))..
+      "[<]<<<[>>>>[>]<+[<]<<<-]<[-]<]>>>>>>[>]<[.<]"
+
+print(src)
-- 
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