1 files changed, 128 insertions, 0 deletions
diff --git a/Lib/irix6/panelparser.py b/Lib/irix6/panelparser.py
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+# Module 'parser'
+#
+# Parse S-expressions output by the Panel Editor
+# (which is written in Scheme so it can't help writing S-expressions).
+#
+# See notes at end of file.
+
+
+whitespace = ' \t\n'
+operators = '()\''
+separators = operators + whitespace + ';' + '"'
+
+
+# Tokenize a string.
+# Return a list of tokens (strings).
+#
+def tokenize_string(s):
+	tokens = []
+	while s:
+		c = s[:1]
+		if c in whitespace:
+			s = s[1:]
+		elif c == ';':
+			s = ''
+		elif c == '"':
+			n = len(s)
+			i = 1
+			while i < n:
+				c = s[i]
+				i = i+1
+				if c == '"': break
+				if c == '\\': i = i+1
+			tokens.append(s[:i])
+			s = s[i:]
+		elif c in operators:
+			tokens.append(c)
+			s = s[1:]
+		else:
+			n = len(s)
+			i = 1
+			while i < n:
+				if s[i] in separators: break
+				i = i+1
+			tokens.append(s[:i])
+			s = s[i:]
+	return tokens
+
+
+# Tokenize a whole file (given as file object, not as file name).
+# Return a list of tokens (strings).
+#
+def tokenize_file(fp):
+	tokens = []
+	while 1:
+		line = fp.readline()
+		if not line: break
+		tokens = tokens + tokenize_string(line)
+	return tokens
+
+
+# Exception raised by parse_exr.
+#
+syntax_error = 'syntax error'
+
+
+# Parse an S-expression.
+# Input is a list of tokens as returned by tokenize_*().
+# Return a pair (expr, tokens)
+# where expr is a list representing the s-expression,
+# and tokens contains the remaining tokens.
+# May raise syntax_error.
+#
+def parse_expr(tokens):
+	if (not tokens) or tokens[0] <> '(':
+		raise syntax_error, 'expected "("'
+	tokens = tokens[1:]
+	expr = []
+	while 1:
+		if not tokens:
+			raise syntax_error, 'missing ")"'
+		if tokens[0] == ')':
+			return expr, tokens[1:]
+		elif tokens[0] == '(':
+			subexpr, tokens = parse_expr(tokens)
+			expr.append(subexpr)
+		else:
+			expr.append(tokens[0])
+			tokens = tokens[1:]
+
+
+# Parse a file (given as file object, not as file name).
+# Return a list of parsed S-expressions found at the top level.
+#
+def parse_file(fp):
+	tokens = tokenize_file(fp)
+	exprlist = []
+	while tokens:
+		expr, tokens = parse_expr(tokens)
+		exprlist.append(expr)
+	return exprlist
+
+
+# EXAMPLE:
+#
+# The input
+#	'(hip (hop hur-ray))'
+#
+# passed to tokenize_string() returns the token list
+#	['(', 'hip', '(', 'hop', 'hur-ray', ')', ')']
+#
+# When this is passed to parse_expr() it returns the expression
+#	['hip', ['hop', 'hur-ray']]
+# plus an empty token list (because there are no tokens left.
+#
+# When a file containing the example is passed to parse_file() it returns
+# a list whose only element is the output of parse_expr() above:
+#	[['hip', ['hop', 'hur-ray']]]
+
+
+# TOKENIZING:
+#
+# Comments start with semicolon (;) and continue till the end of the line.
+#
+# Tokens are separated by whitespace, except the following characters
+# always form a separate token (outside strings):
+#	( ) '
+# Strings are enclosed in double quotes (") and backslash (\) is used
+# as escape character in strings.