Default behavior when no regex matches == exception?!

[cjeffery]

Hi,

When no regular expression matches a character, lex and flex copy that character to the standard output.
Recently I learned that JFlex yylex() throws an exception when no regular expression matches a character.
This might be a feature and not a bug, but since it caused program termination with a cryptic error message
on a specification that flex would process to completion, maybe it is a bug. Is there a command line option
to get jflex to behave like flex, or better yet, can the default behavior be like flex and the exception be available
as a command line option?

Cheers
Clint Jeffery

[lsf37]

The behaviour is intentional. JFlex is not trying to be fully compatible with lex and flex, its heritage is more through JLex, which it does have a compatibility mode for.

It usually doesn't make sense in Java for a scanner to interact with System.out without that being explicitly requested, but you can use %standalone in the options part of the scanner spec for getting this particular lex/flex behaviour. This option also declares a main method so that scanner can be run from the command line.

[cjeffery]

Thanks for the clarification. I think you can close this one then!