Conversion of semantic values to string objects

[Markus Elfring]

Hello,

I try to develop a small grammar that I derive from descriptions in your C++
tutorial.
http://www.gnu.org/software/bison/manual/html_node/A-Complete-C_002b_002b-Example.html

Unfortunately, I stumble on error messages like the following during the build
process on my openSUSE system.

...
Building parser with bison 3.0
parser.ypp:109.64-65: error: $5 of ‘assignment’ has no declared type
             driver.parameters[($1 += '.') += $3] = string_cast($5);
                                                                ^^
parser.ypp:111.79-80: error: $3 of ‘assignment’ has no declared type
             | "identifier" ASSIGN value { driver.parameters[$1] =
string_cast($3); }
                                                                               
^^
parser.ypp:112.83-84: error: $4 of ‘assignment’ has no declared type
             | "identifier" DOT ASSIGN value { driver.parameters[$1] =
string_cast($4); }

   ^^
make[2]: *** [parser.cpp] Error 1
...


I guess that I need a bit more help with the handling of semantic values in
grammar actions when it seems that I do eventually not want to use a
specification like "%token <std::string> IDENTIFIER ..." for the detection of a
"rvalue" in my use case.
http://www.gnu.org/software/bison/manual/html_node/Calc_002b_002b-Parser.html
http://www.gnu.org/software/bison/manual/html_node/Action-Types.html

I would appreciate your advices.

Regards,
Markus