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