what does that mean?
On Feb 8, 12:18 pm, David Beazley <[email protected]> wrote:
> You're not propagating values correctly by assigning to p[0].
> For example, in the p_statement_expr() rule.
>
> -Dave
>
> On Sun 08/02/09 6:20 AM , matio [email protected] sent:
>
>
>
> > I've been using ply & have extended the example slightly:
>
> > [code]
> > <code>
> > import ply.lex as lex
>
> > reserved = {'print':'PRINT', 'quit' : 'QUIT'}
>
> > # List of token names. This is always required
> > tokens = [
> > 'NUMBER',
> > 'NAME',
> > 'PLUS',
> > 'MINUS',
> > 'TIMES',
> > 'DIVIDE',
> > 'LPAREN',
> > 'RPAREN',
> > 'EQUALS',
> > 'STRING',
> > ] + list(reserved.values())
>
> > # Regular expression rules for simple tokens
> > t_PLUS = r'\+'
> > t_MINUS = r'-'
> > t_TIMES = r'\*'
> > t_DIVIDE = r'/'
> > t_LPAREN = r'\('
> > t_RPAREN = r'\)'
> > t_EQUALS = r'='
>
> > def t_NAME(t):
> > r'[a-zA-Z_][a-zA-Z_0-9]*'
> > t.type = reserved.get(t.value,'NAME') # Check for reserved
> > words
> > return t
>
> > # A regular expression rule with some action code
> > def t_NUMBER(t):
> > r'\d+'
> > t.value = int(t.value)
> > return t
>
> > # Define a rule so we can track line numbers
> > def t_newline(t):
> > r'\n+'
> > t.lexer.lineno += len(t.value)
>
> > def t_STRING(t):
> > r'\"([^\\"]|(\\.))*\"'
> > escaped = 0
> > str = t.value[1:-1]
> > new_str = ""
> > for i in range(0, len(str)):
> > c = str[i]
> > if escaped:
> > if c == "n":
> > c = "\n"
> > elif c == "t":
> > c = "\t"
> > new_str += c
> > escaped = 0
> > else:
> > if c == "\\":
> > escaped = 1
> > else:
> > new_str += c
> > t.value = new_str
> > return t
>
> > # A string containing ignored characters (spaces and tabs)
> > t_ignore = ' \t'
>
> > # Error handling rule
> > def t_error(t):
> > print "Illegal character '%s'" % t.value[0]
> > t.lexer.skip(1)
>
> > # Build the lexer
> > lexer = lex.lex()
> > [/code]
> > </code>
>
> > &
>
> > [code]
> > <code>
> > import ply.yacc as yacc
> > import sys
>
> > # Get the token map from the lexer. This is required.
> > from calclex import tokens
>
> > names = {}
> > def p_statement_assign(t):
> > 'statement : NAME EQUALS expression'
> > names[t[1]] = t[3]
>
> > def p_statement_expr(t):
> > 'statement : expression'
> > if t[1] != None:
> > print t[1]
> > else:
> > pass
>
> > def p_expression_name(t):
> > 'expression : NAME'
> > try:
> > t[0] = names[t[1]]
> > except LookupError:
> > print "Undefined name '%s'" % t[1]
> > t[0] = 0
>
> > def p_expression_plus(p):
> > 'expression : expression PLUS term'
> > p[0] = p[1] + p[3]
>
> > def p_expression_minus(p):
> > 'expression : expression MINUS term'
> > p[0] = p[1] - p[3]
>
> > def p_expression_term(p):
> > 'expression : term'
> > p[0] = p[1]
>
> > def p_term_times(p):
> > 'term : term TIMES factor'
> > p[0] = p[1] * p[3]
>
> > def p_term_div(p):
> > 'term : term DIVIDE factor'
> > p[0] = p[1] / p[3]
>
> > def p_term_factor(p):
> > 'term : factor'
> > p[0] = p[1]
>
> > def p_factor_num(p):
> > 'factor : NUMBER'
> > p[0] = p[1]
>
> > def p_factor_expr(p):
> > 'factor : LPAREN expression RPAREN'
> > p[0] = p[2]
>
> > def p_print(p):
> > '''expression : PRINT LPAREN STRING RPAREN
> > | PRINT LPAREN expression RPAREN'''
> > p[0] = p[3]
>
> > def p_quit(p):
> > 'expression : QUIT'
> > sys.exit()
>
> > # Error rule for syntax errors
> > def p_error(p):
> > print "Syntax error in input!"
>
> > # Build the parser
> > parser = yacc.yacc()
>
> > if len(sys.argv) == 1:
> > while True:
> > try:
> > s = raw_input('calc > ')
> > except EOFError:
> > break
> > if not s: continue
> > result = parser.parse(s)
> > print result
>
> > elif sys.argv[1] == "-f":
> > f = open(sys.argv[2], "r")
> > s = f.readlines()
> > for line in s:
> > result = parser.parse(line)
> > if result != None:
> > print "result != none"
> > print result
> > [/code]
> > </code>
> > When I run print("hello") it says:
> > hello
> > none
> > calc>
>
> > What's wrong?
> > I also posted it
> > athttp://ubuntuforums.org/showthread.php?p=6698006#post6698006>
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