On 12:19 Thursday, 21 May 2020 +0200, Bill Allombert wrote
> On Wed, May 20, 2020 at 10:03:08PM -0700, Manoj Srivastava wrote:
> > While it is true that the change was incompatible wwith what we
> > had befire, the change was made almost four and a half years ago. I
> > suspect we have gotten used to it now; and changing it back would just
> > cause issues.
>
> Is the new behaviour documented now ?
> This is needed to use yyinput() properly.
See below. The yyinput usage is demonstrated in an example in
the info node about generating C++ scanners.
> The commit message does give any rationale or information about this.
>
> > I guess this is the new normal?
>
> Do you mean that sacarstically ?
What make you think that? After 4.5 years of this being the
default, stating that yyinput returning NULL is normal seems like a
statement of fact.
Manoj
In Node: 18 Generating C++ Scanners
=======================================================
Here is an example of a simple C++ scanner:
// An example of using the flex C++ scanner class.
%{
#include <iostream>
using namespace std;
int mylineno = 0;
%}
%option noyywrap c++
string \"[^\n"]+\"
ws [ \t]+
alpha [A-Za-z]
dig [0-9]
name ({alpha}|{dig}|\$)({alpha}|{dig}|[_.\-/$])*
num1 [-+]?{dig}+\.?([eE][-+]?{dig}+)?
num2 [-+]?{dig}*\.{dig}+([eE][-+]?{dig}+)?
number {num1}|{num2}
%%
{ws} /* skip blanks and tabs */
"/*" {
int c;
while((c = yyinput()) != 0)
{
if(c == '\n')
++mylineno;
else if(c == '*')
{
if((c = yyinput()) == '/')
break;
else
unput(c);
}
}
}
{number} cout << "number " << YYText() << '\n';
\n mylineno++;
{name} cout << "name " << YYText() << '\n';
{string} cout << "string " << YYText() << '\n';
%%
// This include is required if main() is an another source file.
//#include <FlexLexer.h>
int main( int /* argc */, char** /* argv */ )
{
FlexLexer* lexer = new yyFlexLexer;
while(lexer->yylex() != 0)
;
return 0;
}
--
Two wrights don't make a rong, they make an airplane. Or bicycles.
Manoj Srivastava <sriva...@acm.org>
4096R/C5779A1C E37E 5EC5 2A01 DA25 AD20 05B6 CF48 9438 C577 9A1C
