arithmetic.g4 question

[Willy Andrianarisoa]

I try to implement formula builder project , i start as a scratch the arithmetic.g4 grammar available in antlr4 github (https://github.com/antlr/grammars-v4/blob/master/arithmetic/arithmetic.g4)

I start to test it , with some inputs,

When i try to analyze (with ANTLR input below

10 < 10G

it didn"treport any error ! 

Is this correct (10G is a bad input i suppose)?

I'm a little bit stucked with it. I t

I put in attachments ,  the grammar and the parsetree result

Thanks for any help

Will

[Michael Rachow]

Hi,

maybe extraneous input at the end is finally not shown.

You might try
10G>10

possibly with -token to see more.

Regards,
Michael

[Willy Andrianarisoa]

Hi,

Let me check and il will be back to you.

Thanks

Regards

Willy

[Ken Domino]

Antlr has no syntax to declare a start rule, so it could be any parser rule. But, that can lead to confusing behavior. '10 < 10G' is illegal input with rule "file_". But, if you try parsing '10 < 10G' from rule "expression", the parse will succeed and not produce an error. Why? This is because "expression" is not an EOF-terminated rule. Instead, the parser backs up to the point of a valid expression, does not output any error, and succeeds. This is by design. Unfortunately, it was also a source of unchecked errors in several important programming language grammars in grammars-v4. Consequently, EOF was added to every start rule. https://github.com/antlr/grammars-v4/pull/2675. --Ken

[Michael Rachow]

Thanks Ken,
learned something.
Regards,
Michael