now the Python binding has an alternative representation for abstract trees which is composed of Python objects. The new representation is not integrated with the core runtime yet

1 files changed, 169 insertions, 0 deletions

diff --git a/src/runtime/python/pgf/expr.py b/src/runtime/python/pgf/expr.py
new file mode 100644
index 000000000..83cccd39f
--- /dev/null
+++ b/src/runtime/python/pgf/expr.py
@@ -0,0 +1,169 @@
+import pgf.binding
+import StringIO
+
+class App:
+	"""An application of a function to an argument"""
+
+	def __init__(self, fun, arg):
+		self.fun = fun
+		self.arg = arg
+
+	def showExpr(self, prec):
+		s = self.fun.showExpr(3) + " " + self.arg.showExpr(4)
+		if prec > 3:
+			s = "(" + s + ")"
+		return s
+
+	def __str__(self):
+		return self.showExpr(0)
+
+class Lit:
+	"""A literal value"""
+
+	def __init__(self, value):
+		self.value = value
+
+	def showExpr(self, prec):
+		if isinstance(self.value, str):
+			return '"' + self.value + '"'
+		else:
+			return str(self.value)
+
+	def __str__(self):
+		return self.showExpr(0)
+
+class Meta:
+	"""A meta variable"""
+
+	def __init__(self, metaid):
+		self.metaid = metaid
+
+	def showExpr(self, prec):
+		return "?"
+
+	def __str__(self):
+		return self.showExpr(0)
+
+class Fun:
+	"""A function name"""
+
+	def __init__(self, name):
+		self.name = name
+
+	def showExpr(self, prec):
+		return self.name
+
+	def __str__(self):
+		return self.showExpr(0)
+
+class __ExprParser:
+	# token types
+	TOKEN_UNKNOWN  = 0
+	TOKEN_LPARENT  = 1
+	TOKEN_RPARENT  = 2
+	TOKEN_QUESTION = 3
+	TOKEN_IDENT    = 4
+	TOKEN_STRING   = 5
+	TOKEN_INT      = 6
+	TOKEN_FLOAT    = 7
+	TOKEN_EOF      = 8
+
+	def __init__(self, fh):
+		self.ch = ' '
+		self.fh = fh
+		self.token = self.TOKEN_UNKNOWN
+		self.token_value = ""
+		self.readToken()
+
+	def readToken(self):
+		while self.ch.isspace():
+			self.ch = self.fh.read(1);
+
+		self.token_value = ""
+
+		if self.ch == '(':
+			self.ch = self.fh.read(1);
+			self.token = self.TOKEN_LPARENT
+		elif self.ch == ')':
+			self.ch = self.fh.read(1);
+			self.token = self.TOKEN_RPARENT
+		elif self.ch == '?':
+			self.ch = self.fh.read(1);
+			self.token = self.TOKEN_QUESTION
+		elif (self.ch.isalpha() or self.ch == '_'):
+			self.token = self.TOKEN_IDENT
+			while (self.ch.isalnum() or self.ch == '_' or self.ch == "'"):
+				self.token_value = self.token_value + self.ch
+				self.ch = self.fh.read(1)
+		elif self.ch == '"':
+			self.ch = self.fh.read(1)
+			self.token = self.TOKEN_STRING
+			while self.ch != '"':
+				if self.ch == '':
+					raise pgf.ParseError("Missing quotation mark")
+				self.token_value = self.token_value + self.ch
+				self.ch = self.fh.read(1)
+			self.ch = self.fh.read(1)
+		elif self.ch.isdigit():
+			self.token = self.TOKEN_INT
+			while self.ch.isdigit():
+				self.token_value = self.token_value + self.ch
+				self.ch = self.fh.read(1)
+				
+			if self.ch == '.':
+				self.token = self.TOKEN_FLOAT
+
+				self.token_value = self.token_value + self.ch
+				self.ch = self.fh.read(1)
+				
+				while self.ch.isdigit():
+					self.token_value = self.token_value + self.ch
+					self.ch = self.fh.read(1)
+				
+		elif self.ch == '':
+			self.token = self.TOKEN_EOF
+		else:
+			self.token = self.TOKEN_UNKNOWN
+
+	def parseTerm(self):
+		if self.token == self.TOKEN_IDENT:
+			e = Fun(self.token_value)
+			self.readToken()
+			return e
+		elif self.token == self.TOKEN_LPARENT:
+			self.readToken()
+			e = self.parseExpr()
+			if self.token == self.TOKEN_RPARENT:
+				self.readToken()
+				return e;
+			else:
+				raise pgf.ParseError("Missing right parenthesis")
+		elif self.token == self.TOKEN_QUESTION:
+			e = Meta(0)
+			self.readToken()
+			return e
+		elif self.token == self.TOKEN_STRING:
+			e = Lit(self.token_value)
+			self.readToken()
+			return e
+		elif self.token == self.TOKEN_INT:
+			e = Lit(int(self.token_value))
+			self.readToken()
+			return e
+		elif self.token == self.TOKEN_FLOAT:
+			e = Lit(float(self.token_value))
+			self.readToken()
+			return e
+		else:
+			raise pgf.ParseError("Unknown token")
+
+	def parseExpr(self):
+		e = self.parseTerm()
+		while (self.token != self.TOKEN_EOF and
+		       self.token != self.TOKEN_RPARENT):
+			e = App(e, self.parseTerm())
+		return e
+
+def readExpr_py(str):
+	parser = __ExprParser(StringIO.StringIO(str))
+	return parser.parseExpr()