The calculator is printing the result of the parse. It's printing None because you're not propagating values.
-Dave On Sun 08/02/09 7:50 AM , matio [email protected] sent: > > what does that mean? > > On Feb 8, 12:18 pm, David Beazley <[email protected] > om> 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 ma...@hot > mail.co.uk 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&; > gt;> > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "ply-hack" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/ply-hack?hl=en -~----------~----~----~----~------~----~------~--~---
