Now i've changed my rules to include whitespace and then the
[a-zA-Z]+ rule. The code is now:
%{
/**
* First example program for flex
*
*/
#include <stdio.h>
#include <stdlib.h>
%}
%%
is |
am |
are |
where |
was |
be |
being |
been |
do |
does |
did |
should |
can |
could |
has |
have |
had |
go { printf("%s is a verb\n", yytext); }
[ ]+[a-zA-Z]+ { printf("%s is not a verb", yytext); }
.|\n { ECHO; /* normal default anyway */ }
%%
int main(int argc, char **argv)
{
yylex();
}
gut when i try to compile:
$flex test1.l
$gcc lex.yy.c -o test -Wall
i get:
lex.yy.c:1192:16: warning: ‘input’ defined but not used [-Wunused-function]
static int input (void)
^~~~~
lex.yy.c:1149:17: warning: ‘yyunput’ defined but not used
[-Wunused-function]
static void yyunput (int c, char * yy_bp )
^~~~~~~
/tmp/ccAD7IfT.o: In function `yylex':
lex.yy.c:(.text+0x4e6): undefined reference to `yywrap'
/tmp/ccAD7IfT.o: In function `input':
lex.yy.c:(.text+0x10f3): undefined reference to `yywrap'
collect2: error: ld returned 1 exit status
What includes do i need and how to get the warning away ?
best regards!
On 22.02.19 16:20, Jannick wrote:
On Fri, 22 Feb 2019 15:00:51 +0100, [email protected] wrote:
If you replace
[a-zA-Z]+ { printf("%s is not a verb", yytext); }
by
[a-zA-Z]+ printf("'%s' is not a verb\n", yytext);
you will see that the scanner does exactly what it is expected to do, since the
line
.|\n { ECHO; /* normal default anyway */ }
makes it print any character (inkl. '\n') not in [a-zA-Z] to stdout.
Now my question is when i enter one of the verbs it's working normaly like
expected, but when i enter for example 234someword i also get the
messsage %s is not a verb but i've no rule saying that
Well, things are printed in different bits to stdout as you might think in the
first place: The scanner prints each of the leading integers applying the last
rule to each of them, then it pushes 'someword' through the [a-zA-Z]+ rule.
If you apply the suggested change above, you'll see the difference. And if in
addition you replace 'ECHO' (which is a C macro) by a printf statement with
some enclosing tags around the character and a trailing newline, it might be
easier to guess what is happening behind the scenes.
BTW: Not sure if this is the right place to address pure flex issues, but I
leave it with others to judge on this.
HTH.
J.
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