epitsi
asked on
Simple grammar in javacc
It's been 4 years since i have taken a compiler class. I am now trying to create a parser, and I am using javacc for creating the grammar. I will try to demonstrate my problem in the following simple scenario: Let's suppose I need a grammar to read any number of numbers and/or letters, but also to be able and recognize "(" set of characters ")". I have tried something like:
Expression() :
{
<WORD>
| <NUM>
| "(" Foo() ")"
}
Foo() :
{
"0"
| "A"
}
The problem here is that it refuses to recognize exactly what I need since I get a warning that 0 and A will be treated as NUM and WORD respectively. What is the best way to tackle this? Also can someone please give me an example of a recursive rule? Is that even possible? By recursive I refer to the rule calling itself, something like:
Foo() :
{
Foo() ( Foo() )*
}
Expression() :
{
<WORD>
| <NUM>
| "(" Foo() ")"
}
Foo() :
{
"0"
| "A"
}
The problem here is that it refuses to recognize exactly what I need since I get a warning that 0 and A will be treated as NUM and WORD respectively. What is the best way to tackle this? Also can someone please give me an example of a recursive rule? Is that even possible? By recursive I refer to the rule calling itself, something like:
Foo() :
{
Foo() ( Foo() )*
}
ASKER
I will try to keep it as simple as it gets then. I need a javacc file which will be able to parse any text and output it, unless it sees "(0)" in which case it will output "found". For example:
Input: a012(0)
Output: a012found
Input: a012(0)
Output: a012found
What I meant was you want a Java program to do the parsing ?
ASKER CERTIFIED SOLUTION
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Can you please elaborate more on your needs ?