1 # ----------------------------------------------------------------------------- 2 # yacc_notfunc.py 3 # 4 # p_rule not defined as a function 5 # ----------------------------------------------------------------------------- 6 import sys 7 8 if ".." not in sys.path: sys.path.insert(0,"..") 9 import ply.yacc as yacc 10 11 from calclex import tokens 12 13 # Parsing rules 14 precedence = ( 15 ('left','PLUS','MINUS'), 16 ('left','TIMES','DIVIDE'), 17 ('right','UMINUS'), 18 ) 19 20 # dictionary of names 21 names = { } 22 23 p_statement_assign = "Blah" 24 25 def p_statement_expr(t): 26 'statement : expression' 27 print(t[1]) 28 29 def p_expression_binop(t): 30 '''expression : expression PLUS expression 31 | expression MINUS expression 32 | expression TIMES expression 33 | expression DIVIDE expression''' 34 if t[2] == '+' : t[0] = t[1] + t[3] 35 elif t[2] == '-': t[0] = t[1] - t[3] 36 elif t[2] == '*': t[0] = t[1] * t[3] 37 elif t[2] == '/': t[0] = t[1] / t[3] 38 39 def p_expression_uminus(t): 40 'expression : MINUS expression %prec UMINUS' 41 t[0] = -t[2] 42 43 def p_expression_group(t): 44 'expression : LPAREN expression RPAREN' 45 t[0] = t[2] 46 47 def p_expression_number(t): 48 'expression : NUMBER' 49 t[0] = t[1] 50 51 def p_expression_name(t): 52 'expression : NAME' 53 try: 54 t[0] = names[t[1]] 55 except LookupError: 56 print("Undefined name '%s'" % t[1]) 57 t[0] = 0 58 59 def p_error(t): 60 print("Syntax error at '%s'" % t.value) 61 62 yacc.yacc() 63 64 65 66 67
