Initial revision
diff --git a/Lib/irix5/panelparser.py b/Lib/irix5/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.