How would I make something like an if?
On Feb 8, 1:21 pm, David Beazley <[email protected]> wrote: > Either propagate values or don't print the result of the parse. > > -Dave > > On Sun 08/02/09 8:04 AM , matio [email protected] sent: > > > > > how do I fix it? > > > On Feb 8, 12:58 pm, David Beazley <[email protected] > > om> wrote:> 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 ma...@hot > > mail.co.uk 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&; > > amp;> > gt;> --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "ply-hack" group. 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