Odd bug with 'solve'

[parisse]

There is special code in the parser to detect i inside a loop as an index, but inside a solve command or other CAS expressions, i is and will remain sqrt(-1) (unless you activate some compatibility mode, for example inside Xcas xcas_mode(1) will activate maple compatibility where sqrt(-1)==I).
Most calculators and some desktop programs prefer to have a special i letter, but it is hard to get this character on a desktop keyboard and moreover it is not the same unicode char everywhere which means that if you are using a special i you will probably have to stay with the same program/calculator (probably a reason to get calc maker happy!).
I strongly believe it is much better to have a standard letter for sqrt(-1), and I think lowercase i is better than uppercase I (but I leave the choice to the end user). The Xcas lexer accepts the following versions of i, from input_lexer.ll

Code:


"i"            index_status(yyextra)=1; if (xcas_mode(yyextra) > 0 || !i_sqrt_minus1(yyextra)) { (*yylval)=i__IDNT_e; return T_SYMBOL; } else { (*yylval) = cst_i; return T_LITERAL;};
"ί"                      index_status(yyextra)=1; (*yylval) = cst_i; return T_LITERAL;
"?"                     index_status(yyextra)=1; (*yylval) = cst_i; return T_LITERAL;
""                      index_status(yyextra)=1; (*yylval) = cst_i; return T_LITERAL;
\xa1                    index_status(yyextra)=1; (*yylval) = cst_i; return T_LITERAL;
  /* \xef\xbd\x89            index_status(yyextra)=1; (*yylval) = cst_i; return T_LITERAL; */
\xe2\x81\xb1            index_status(yyextra)=1; (*yylval) = cst_i; return T_LITERAL;
"I"                     index_status(yyextra)=1; if (python_compat(yyextra)>=0 && (xcas_mode(yyextra)==0 || xcas_mode(yyextra)==3 || rpn_mode(yyextra)) ) { return find_or_make_symbol(yytext,(*yylval),yyscanner,true,yyextra); } else { (*yylval) = cst_i; return T_LITERAL; };
"%i"            index_status(yyextra)=1; (*yylval) = cst_i; return T_LITERAL;