diff --git a/.idea/misc.xml b/.idea/misc.xml
index 06aeaca..e0595e7 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -3,5 +3,5 @@
   <component name="JavaScriptSettings">
     <option name="languageLevel" value="ES6" />
   </component>
-  <component name="ProjectRootManager" version="2" project-jdk-name="Python 3.6 (thue)" project-jdk-type="Python SDK" />
+  <component name="ProjectRootManager" version="2" project-jdk-name="Python 3.7 (thue)" project-jdk-type="Python SDK" />
 </project>
\ No newline at end of file
diff --git a/.idea/thue.iml b/.idea/thue.iml
index 85c7612..b9b1fff 100644
--- a/.idea/thue.iml
+++ b/.idea/thue.iml
@@ -4,7 +4,7 @@
     <content url="file://$MODULE_DIR$">
       <excludeFolder url="file://$MODULE_DIR$/venv" />
     </content>
-    <orderEntry type="inheritedJdk" />
+    <orderEntry type="jdk" jdkName="Python 3.7 (thue)" jdkType="Python SDK" />
     <orderEntry type="sourceFolder" forTests="false" />
   </component>
   <component name="TestRunnerService">
diff --git a/rethue.py b/rethue.py
deleted file mode 100644
index d15ab9b..0000000
--- a/rethue.py
+++ /dev/null
@@ -1,49 +0,0 @@
-from lark import Lark
-
-grammar = r'''
-suite: prod*
-
-prod: _named_prod
-
-_named_prod: _direct_prod | alias
-_direct_prod: _compound_prod | _rule_prod | _literal_prod | _abstract_prod
-_abstract_prod: output
-_compound_prod: cont | sing
-_rule_prod: full | part
-_literal_prod: lit | ref
-
-cont: "{" suite "}"             // continual production
-sing: "[" suite "]"             // singular production
-
-alias: ref "=" prod             // production alias
-full: _direct_prod "=>" prod    // full application
-part: ctx "::=" prod            // partial application
-
-output: "~" prod
-
-lit: STRING
-ref: CNAME
-ctx: REGEX
-
-CNAME: /[a-z_][a-z0-9_]*/i
-STRING: /(r)?(['"])(.*?)(?<!\\)\2/
-REGEX: /(r)?([\/])(.*?)(?<!\\)\2(i)?/
-
-%import common.WS
-%ignore WS
-'''
-
-
-def main():
-    lrk = Lark(grammar, start='suite')
-
-    with open('sample.ret') as f:
-        src = f.read()
-
-    tree = lrk.parse(src)
-
-    print(tree.pretty())
-
-
-if __name__ == '__main__':
-    main()
diff --git a/sub.py b/sub.py
new file mode 100644
index 0000000..f81af21
--- /dev/null
+++ b/sub.py
@@ -0,0 +1,231 @@
+import re
+
+from lark import Lark, InlineTransformer, Transformer
+
+grammar = r'''
+program: suite
+
+suite: prod*
+
+?prod: _named_prod | _direct_prod
+
+_named_prod     : alias
+_direct_prod    : _compound_prod | _rule_prod | _literal_prod | _abstract_prod
+_abstract_prod  : output
+_compound_prod  : cont | sing
+_rule_prod      : full | part
+_literal_prod   : lit | ref
+
+alias : name "=" prod               // production alias
+output: "~" prod                    // output production
+
+cont  : "{" suite "}"               // continual production
+sing  : "[" suite "]"               // singular production
+
+full  : _direct_prod "=>" prod      // full application
+part  : ctx "::=" prod              // partial application
+ref   : name                        // production reference
+
+lit   : STRING                      // literal production
+name  : CNAME                       // named production
+
+ctx   : REGEX
+
+CNAME : /[a-z_][a-z0-9_]*/i
+STRING: /(r)?(['"])(.*?)(?<!\\)\2/
+REGEX : /(r)?([\/])(.*?)(?<!\\)\2(i)?/
+
+%import common.WS
+%ignore WS
+'''
+
+
+class Context:
+    def __init__(self, string, match=None):
+        if match is None:
+            match = re.match(r'^.*$', string)
+
+        self.string = string
+        self.match = match
+
+    def enter(self):
+        return Context(self.string, self.match)
+
+    def exit(self, ctx):
+        diff = self.string != ctx.string
+        self.string = ctx.string
+        self.match = ctx.match
+        return diff
+
+    def expand(self, fmt):
+        self.string = self.match.expand(fmt)
+        self.match = ALL_PAT.match(self.string)
+
+    def __str__(self):
+        return f'Ctx[{self.string!r} {self.match[0]!r} {self.match.groups()}]'
+
+
+class Literal:
+    def __init__(self, fmt):
+        self.fmt = fmt
+
+    def apply(self, ctx):
+        ctx_ = ctx.enter()
+        ctx_.expand(self.fmt)
+        return ctx.exit(ctx_)
+
+    def __str__(self):
+        return f'Literal[{self.fmt}]'
+
+
+class Full:
+    def __init__(self, lhs, rhs):
+        self.lhs = lhs
+        self.rhs = rhs
+
+    def apply(self, ctx):
+        ctx_ = ctx.enter()
+        self.lhs.apply(ctx_)
+        self.rhs.apply(ctx_)
+        return ctx.exit(ctx_)
+
+    def __str__(self):
+        return f'Full[{self.lhs} => {self.rhs}]'
+
+
+class Partial:
+    def __init__(self, reg, rhs):
+        self.reg = reg
+        self.pat = re.compile(reg)
+        self.rhs = rhs
+
+    def apply(self, ctx):
+        match = self.pat.search(ctx.string)
+
+        if match:
+            inner = Context(match[0], match)
+            self.rhs.apply(inner)
+            inner.string = ctx.string[:match.start()] + inner.string + ctx.string[match.end():]
+            return ctx.exit(inner)
+
+        return False
+
+    def __str__(self):
+        return f'Part[{self.reg} ::= {self.rhs}]'
+
+
+class Suite:
+    def __init__(self, prods, ctx=None):
+        if ctx is None:
+            ctx = Context('')
+
+        self.prods = prods
+        self.ctx = ctx
+
+    def apply(self, ctx):
+        ctx_ = ctx.enter()
+        for prod in self.prods:
+            if prod.apply(ctx_):
+                break
+        return ctx.exit(ctx_)
+
+    def __str__(self):
+        prod_list = ' '.join(map(str, self.prods))
+        return f'Suite[{prod_list}]'
+
+
+class Continual:
+    def __init__(self, suite):
+        self.suite = suite
+
+    def apply(self, ctx):
+        res = False
+        while self.suite.apply(ctx):
+            res = True
+        return res
+
+    def __str__(self):
+        return f'Continual[{self.suite}]'
+
+
+class Singular:
+    def __init__(self, suite):
+        self.suite = suite
+
+    def apply(self, ctx):
+        self.suite.apply(ctx)
+
+    def __str__(self):
+        return f'Singular[{self.suite}]'
+
+
+class Program:
+    def __init__(self, suite):
+        self.suite = suite
+
+    def run(self, init=''):
+        ctx = Context(init)
+        self.suite.apply(ctx)
+        return ctx.string
+
+    def __str__(self):
+        return f'Program[{self.suite}]'
+
+
+STRING_PAT = re.compile(r'''(r)?(['"])(.*?)(?<!\\)\2''')
+REGEX_PAT = re.compile(r'''(r)?([/])(.*?)(?<!\\)\2(i)?''')
+ALL_PAT = re.compile(r'''^.*$''')
+
+
+class ProductionTransformer(Transformer):
+    def suite(self, prods):
+        return Suite(prods)
+
+    def lit(self, prods):
+        fmt, = prods
+        match = STRING_PAT.match(fmt)
+        return Literal(match[3])
+
+    def ctx(self, prods):
+        reg, = prods
+        match = REGEX_PAT.match(reg)
+        return re.compile(match[3])
+
+    def full(self, prods):
+        lhs, rhs = prods
+        return Full(lhs, rhs)
+
+    def part(self, prods):
+        pat, rhs = prods
+        return Partial(pat, rhs)
+
+    def cont(self, prods):
+        suite, = prods
+        return Continual(suite)
+
+    def sing(self, prods):
+        suite, = prods
+        return Singular(suite)
+
+    def program(self, prods):
+        suite, = prods
+        return Program(suite)
+
+
+def main():
+    lrk = Lark(grammar, start='program')
+
+    with open('testing.ret') as f:
+        src = f.read()
+
+    tree = lrk.parse(src)
+    print(tree.pretty())
+
+    tform = ProductionTransformer()
+    pgm = tform.transform(tree)
+    print(pgm)
+    print(pgm.run())
+
+
+if __name__ == '__main__':
+    main()
diff --git a/testing.ret b/testing.ret
new file mode 100644
index 0000000..b21bc22
--- /dev/null
+++ b/testing.ret
@@ -0,0 +1 @@
+'hello there' => /(.*)\s+(.*)/ ::= '\g<0> \2 \1'
\ No newline at end of file