[antlr-interest] missing tokens and strange behaviour regarding some chars

[Nieves.Salor.Moral at esa.int]

Hello to everyone!

I am new with ANTLR but not with compilers. Before I explain the problem 
I'll  try to explain a little bit the situation background.

I am trying to design for a custom language, first a syntax highlighter 
and second a module that can store the information in a DB (so in essence 
would be creating a compiler with its output as SQL queries).
My input language is defined in EBNF, thus it has left-recursion and 
ambiguity. In order to solve it, I have changed it a little to avoid those 
problems and mostly I have managed it without using predicates or 
backtracking. 

Working with ANTLR Works, I am debugging the grammar with different 
examples (just the parser), before adding the highlighting code in the 
StringTemplate. but I get these strange errors, mostly regarding 
NoViableAltException.

One problem for example is trying to define negative expressions with the 
simple_factor rule.
So when I debug expressions like 500 or +500 in the simple_factor, I don't 
get an error. But If I try -500, I get the NoViableAltException. Also if I 
change - for another symbol like @, it also work when I try @500. I have 
traced all the possibilities in the different possibilities in 
simple_factor, but in no one the first symbol can be a negative symbol. 
And I am lost as to why this can happen. I add the whole grammar because 
it is quite big to paste it.

Another problem that appears is that sometimes tokens are missed when 
reading, so for example if I have an input beginning with 'initiate and 
confirm',  ANTLR reads 'conf' and loses the first characters. With the 
same grammar that I have posted. One example of this problem goes with the 
input 'initiate and confirm sys_stop of SCOE_1553 of LLCS of EGSE of 
System of ODB' with the rule initiate_and_confirm_step_statement.

Thanks in advance for any input

Nieves Salor Moral

addition_operator:  ADDITION_OPERATOR
        ;

ADDITION_OPERATOR
        :       '+'|'-'
        ;
 
 UNSIGNED_INTEGER
        :       DIGIT+
        ;

simple_factor
        :       addition_operator simple_factor
        |       NEGATION_BOOLEAN_OPERATOR simple_factor
        |       constant
        |       '('expression ')'
        |       function
        |       object_property_request
        |       OBJECT_TYPE partial_path
        |       'ask user' '(' expression ('default' expression)? ')' 
('expect' predefined_type)?
        ; 

constant:       BOOLEAN_CONSTANT
        |       UNSIGNED_INTEGER ( numeric_constant| 
RELATIVE_TIME_CONSTANT)
        |       RELATIVE_TIME_CONSTANT
        |       string_constant
        |       HEXADECIMAL_CONSTANT
        ;
real_constant
        :       ('.' UNSIGNED_INTEGER)? ('e' addition_operator? 
UNSIGNED_INTEGER)? 
        ;

numeric_constant
        :        real_constant engineering_units?
        ;


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