1 # ----------------------------------------------------------------------------- 2 # yacc_unicode_literals 3 # 4 # Test for unicode literals on Python 2.x 5 # ----------------------------------------------------------------------------- 6 from __future__ import unicode_literals 7 8 import sys 9 10 if ".." not in sys.path: sys.path.insert(0,"..") 11 import ply.yacc as yacc 12 13 from calclex import tokens 14 15 # Parsing rules 16 precedence = ( 17 ('left','PLUS','MINUS'), 18 ('left','TIMES','DIVIDE'), 19 ('right','UMINUS'), 20 ) 21 22 # dictionary of names 23 names = { } 24 25 def p_statement_assign(t): 26 'statement : NAME EQUALS expression' 27 names[t[1]] = t[3] 28 29 def p_statement_expr(t): 30 'statement : expression' 31 print(t[1]) 32 33 def p_expression_binop(t): 34 '''expression : expression PLUS expression 35 | expression MINUS expression 36 | expression TIMES expression 37 | expression DIVIDE expression''' 38 if t[2] == '+' : t[0] = t[1] + t[3] 39 elif t[2] == '-': t[0] = t[1] - t[3] 40 elif t[2] == '*': t[0] = t[1] * t[3] 41 elif t[2] == '/': t[0] = t[1] / t[3] 42 43 def p_expression_uminus(t): 44 'expression : MINUS expression %prec UMINUS' 45 t[0] = -t[2] 46 47 def p_expression_group(t): 48 'expression : LPAREN expression RPAREN' 49 t[0] = t[2] 50 51 def p_expression_number(t): 52 'expression : NUMBER' 53 t[0] = t[1] 54 55 def p_expression_name(t): 56 'expression : NAME' 57 try: 58 t[0] = names[t[1]] 59 except LookupError: 60 print("Undefined name '%s'" % t[1]) 61 t[0] = 0 62 63 def p_error(t): 64 print("Syntax error at '%s'" % t.value) 65 66 yacc.yacc() 67 68 69 70 71
