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1 # -----------------------------------------------------------------------------
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2 # yacc_error7.py
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3 #
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4 # Panic mode recovery test using deprecated functionality
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5 # -----------------------------------------------------------------------------
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6 import sys
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7
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8 if ".." not in sys.path: sys.path.insert(0,"..")
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9 import ply.yacc as yacc
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10
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11 from calclex import tokens
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12
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13 # Parsing rules
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14 precedence = (
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15 ('left','PLUS','MINUS'),
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16 ('left','TIMES','DIVIDE'),
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17 ('right','UMINUS'),
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18 )
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19
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20 def p_statements(t):
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21 'statements : statements statement'
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22 pass
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23
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24 def p_statements_1(t):
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25 'statements : statement'
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26 pass
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27
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28 def p_statement_assign(p):
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29 'statement : LPAREN NAME EQUALS expression RPAREN'
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30 print("%s=%s" % (p[2],p[4]))
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31
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32 def p_statement_expr(t):
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33 'statement : LPAREN expression RPAREN'
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34 print(t[1])
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35
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36 def p_expression_binop(t):
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37 '''expression : expression PLUS expression
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38 | expression MINUS expression
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39 | expression TIMES expression
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40 | expression DIVIDE expression'''
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41 if t[2] == '+' : t[0] = t[1] + t[3]
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42 elif t[2] == '-': t[0] = t[1] - t[3]
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43 elif t[2] == '*': t[0] = t[1] * t[3]
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44 elif t[2] == '/': t[0] = t[1] / t[3]
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45
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46 def p_expression_uminus(t):
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47 'expression : MINUS expression %prec UMINUS'
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48 t[0] = -t[2]
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49
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50 def p_expression_number(t):
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51 'expression : NUMBER'
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52 t[0] = t[1]
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53
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54 def p_error(p):
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55 if p:
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56 print("Line %d: Syntax error at '%s'" % (p.lineno, p.value))
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57 # Scan ahead looking for a name token
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58 while True:
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59 tok = yacc.token()
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60 if not tok or tok.type == 'RPAREN':
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61 break
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62 if tok:
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63 yacc.restart()
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64 return None
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65
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66 parser = yacc.yacc()
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67 import calclex
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68 calclex.lexer.lineno=1
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69
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70 parser.parse("""
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71 (a = 3 + 4)
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72 (b = 4 + * 5 - 6 + *)
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73 (c = 10 + 11)
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74 """)
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75
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76
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77
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78
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79
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80
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