peckham@svax.cs.cornell.edu (Stephen Peckham) (10/21/87)
I've run across two problems using lex that appear to be bugs.
First, if the first rule in the lex specification is "\<|" (without quotes),
the generated code won't compile. (A "case" outside of
a switch is generated.) No lex error is given for the "|" operator
followed by the end-of-line. Second, a specification with the lookahead
operator doesn't work correctly, and depends on the order of rules.
An excerpt follows:
%%
<W>([\ \n]*)/("<") {BEGIN C;}
<W>([\ \n]*) {BEGIN S;}
<C>"<"
<INITIAL>"<|" {BEGIN W;}
On input "<| <..." the following tokens are returned:
"<|" (rule 4)
" " (rule 1)
"<" (rule 1)--this sure looks fishy.
If I move rule 3 (<C>...) to the beginning of the specification,
then the third token returned is "<", and it is returned by the
moved rule. Of course, this rule should have matched in the first place.
I'm running a Sep 15 1986 version of lex on a Sun 3/50.
Are these known bugs, or am I misunderstanding something?
If someone is interested, I can send more details.
Steve Peckham
peckham@svax.cs.cornell.edu