1# ----------------------------------------------------------------------------- 2# yacc_error5.py 3# 4# Lineno and position tracking with error tokens 5# ----------------------------------------------------------------------------- 6import sys 7 8if ".." not in sys.path: sys.path.insert(0,"..") 9import ply.yacc as yacc 10 11from calclex import tokens 12 13# Parsing rules 14precedence = ( 15 ('left','PLUS','MINUS'), 16 ('left','TIMES','DIVIDE'), 17 ('right','UMINUS'), 18 ) 19 20# dictionary of names 21names = { } 22 23def p_statement_assign(t): 24 'statement : NAME EQUALS expression' 25 names[t[1]] = t[3] 26 27def p_statement_assign_error(t): 28 'statement : NAME EQUALS error' 29 line_start, line_end = t.linespan(3) 30 pos_start, pos_end = t.lexspan(3) 31 print("Assignment Error at %d:%d to %d:%d" % (line_start,pos_start,line_end,pos_end)) 32 33def p_statement_expr(t): 34 'statement : expression' 35 print(t[1]) 36 37def p_expression_binop(t): 38 '''expression : expression PLUS expression 39 | expression MINUS expression 40 | expression TIMES expression 41 | expression DIVIDE expression''' 42 if t[2] == '+' : t[0] = t[1] + t[3] 43 elif t[2] == '-': t[0] = t[1] - t[3] 44 elif t[2] == '*': t[0] = t[1] * t[3] 45 elif t[2] == '/': t[0] = t[1] / t[3] 46 47def p_expression_uminus(t): 48 'expression : MINUS expression %prec UMINUS' 49 t[0] = -t[2] 50 51def p_expression_group(t): 52 'expression : LPAREN expression RPAREN' 53 line_start, line_end = t.linespan(2) 54 pos_start, pos_end = t.lexspan(2) 55 print("Group at %d:%d to %d:%d" % (line_start,pos_start, line_end, pos_end)) 56 t[0] = t[2] 57 58def p_expression_group_error(t): 59 'expression : LPAREN error RPAREN' 60 line_start, line_end = t.linespan(2) 61 pos_start, pos_end = t.lexspan(2) 62 print("Syntax error at %d:%d to %d:%d" % (line_start,pos_start, line_end, pos_end)) 63 t[0] = 0 64 65def p_expression_number(t): 66 'expression : NUMBER' 67 t[0] = t[1] 68 69def p_expression_name(t): 70 'expression : NAME' 71 try: 72 t[0] = names[t[1]] 73 except LookupError: 74 print("Undefined name '%s'" % t[1]) 75 t[0] = 0 76 77def p_error(t): 78 print("Syntax error at '%s'" % t.value) 79 80parser = yacc.yacc() 81import calclex 82calclex.lexer.lineno=1 83parser.parse(""" 84a = 3 + 85(4*5) + 86(a b c) + 87+ 6 + 7 88""", tracking=True) 89 90 91 92 93 94 95