Create tokens for the indentation/curly braces and the 'if' keyword and then grammar rules that handle sequences of those tokens. I can't go into too much more than that. The examples included with PLY cover quite a bit, really. Have a look at http://www.juanjoconti.com.ar/files/python/ply-examples/GardenSnake/GardenSnake.py.html for a partial implementation of Python called GardenSnake (including the "if" statement).
On Tue, Feb 10, 2009 at 3:33 PM, matio <[email protected]> wrote: > > I meant how would I create an "if" statement, or anything that would > need to be indented/in curly braces? > Would I have to completely re-write the code or is there a way just to > add it in as it is now (I've looked at the examples but it didn't seem > to work)? > > On Feb 9, 6:21 pm, matio <[email protected]> wrote: >> 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. 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 -~----------~----~----~----~------~----~------~--~---
