media_type decode(wchar_t const *ct) {
media_type v;
auto o = ct;
auto r = expect_type(o, v.type);
if (!r) r = expect_slash(o);
if (!r) r = expect_subtype(o, v.subtype);
return v;
}
// Returns the type of a unary expression.
//
// The operand of a unary arithmetic expression (-e, +e, and ~e)
// shall have integer type. The result type the expression is `int`.
//
// The operand of the unary logical expression (!e) shall have
// boolean type. The result type the expression is `bool`.
Type const*
get_type(Unary_op op, Expr const* e)
{
Type const* z = get_int_type();
Type const* b = get_bool_type();
switch (op) {
case num_neg_op:
case num_pos_op:
case bit_not_op:
return expect_type(e, z, z);
case log_not_op:
return expect_type(e, b, b);
default:
break;
}
lingo_unreachable();
}
// Returns the type of a binary expression.
//
// The operands of a binary arithmetic expression (e1 + e2, e1 - e2,
// e1 * e2, e1 / e2, e1 % e2, e1 & e2, e1 | e2, e1 ^ e2, e1 << e2,
// and e1 >> e2) shall have integer type. The result type the
// expression is `int`.
//
// The operands of a binary relational expression (e1 < e2, e1 > e2,
// e1 <= e2, e1 >= e2, e1 == e2, and e1 != e2) shall have integer or
// boolean type. The result type the expression is `bool`.
//
// The operands of a binary logical expression (e1 && e2 and e1 || e2)
// shall have boolean type. The result type the expression is `bool`.
Type const*
get_type(Binary_op op, Expr const* e1, Expr const* e2)
{
Type const* z = get_int_type();
Type const* b = get_bool_type();
switch (op) {
case num_add_op:
case num_sub_op:
case num_mul_op:
case num_div_op:
case num_mod_op:
case bit_and_op:
case bit_or_op:
case bit_xor_op:
case bit_lsh_op:
case bit_rsh_op:
// Arithmetic expressions have integer opreands and results.
return expect_type(e1, e2, z, z);
case rel_eq_op:
case rel_ne_op:
case rel_lt_op:
case rel_gt_op:
case rel_le_op:
case rel_ge_op:
// Relational expressions have any type and the result
// is bool.
return b;
case log_and_op:
case log_or_op:
// Logical expressions have boolean operands and result.
return expect_type(e1, e2, b, b);
default:
break;
}
lingo_unreachable();
}
int32_t expect_subtype(wchar_t const* &ct, std::wstring &subtype) {
return expect_type(ct, subtype);
}
