std::string Operators::what_is_binary_name(const std::string& op)const
{
size_t prec = op_prec(op);
if (prec > 0)
{
return Str::split(binary(prec),' ')[0];
}
return "";
}
/*
* Perform the hard work of evaluation.
*
* This function works because:
* -- all unary operators are right to left associative, and with
* identical precedence
* -- all binary operators are left to right associative
* -- there is only one non-unary and non-binary operator: the quest-colon
*
* If do_eval is 0, the evaluation of operators is not done. This is
* for sequence point operators (&&, || and ?:).
*/
static ppval eval_shrd(struct token_fifo *tf, int minprec, int do_eval)
{
ppval top;
struct ucpp_token *ct;
top.sign = 1;
if (tf->art == tf->nt) goto trunc_err;
ct = tf->t + (tf->art ++);
if (ct->type == LPAR) {
top = eval_shrd(tf, 0, do_eval);
if (tf->art == tf->nt) goto trunc_err;
ct = tf->t + (tf->art ++);
if (ct->type != RPAR) {
error(eval_line, "a right parenthesis was expected");
throw(eval_exception);
}
} else if (ct->type == NUMBER || ct->type == CHAR) {
top = pp_strtoconst(ct->name);
} else if (OP_UN(ct->type)) {
top = eval_opun(ct->type, eval_shrd(tf,
op_prec(ct->type), do_eval));
goto eval_loop;
} else if (ttOP(ct->type)) goto rogue_op_err;
else {
goto invalid_token_err;
}
eval_loop:
if (tf->art == tf->nt) {
return top;
}
ct = tf->t + (tf->art ++);
if (OP_BIN(ct->type)) {
int bp = op_prec(ct->type);
if (bp > minprec) {
ppval tr;
if ((ct->type == LOR && boolval(top))
|| (ct->type == LAND && !boolval(top))) {
tr = eval_shrd(tf, bp, 0);
if (do_eval) {
top.sign = 1;
if (ct->type == LOR)
top.u.sv = big_s_fromint(1);
if (ct->type == LAND)
top.u.sv = big_s_fromint(0);
}
} else {
tr = eval_shrd(tf, bp, do_eval);
if (do_eval)
top = eval_opbin(ct->type, top, tr);
}
goto eval_loop;
}
} else if (ct->type == QUEST) {
int bp = op_prec(QUEST);
ppval r1, r2;
if (bp >= minprec) {
int qv = boolval(top);
r1 = eval_shrd(tf, bp, qv ? do_eval : 0);
if (tf->art == tf->nt) goto trunc_err;
ct = tf->t + (tf->art ++);
if (ct->type != COLON) {
error(eval_line, "a colon was expected");
throw(eval_exception);
}
r2 = eval_shrd(tf, bp, qv ? 0 : do_eval);
if (do_eval) {
if (qv) top = r1; else top = r2;
}
goto eval_loop;
}
}
tf->art --;
return top;
trunc_err:
error(eval_line, "truncated constant integral expression");
throw(eval_exception);
rogue_op_err:
error(eval_line, "rogue operator '%s' in constant integral "
"expression", operators_name[ct->type]);
throw(eval_exception);
invalid_token_err:
error(eval_line, "invalid token in constant integral expression");
throw(eval_exception);
}
