Roland Conybeare
aecabbb144
git-subtree-dir: xo-expression git-subtree-mainline:d0f5ccc1cegit-subtree-split:5ac3c03a0c
103 lines
3.1 KiB
C++
103 lines
3.1 KiB
C++
/** @file Constant.hpp
|
|
*
|
|
* Author: Roland Conybeare
|
|
**/
|
|
|
|
#pragma once
|
|
|
|
#include "ConstantInterface.hpp"
|
|
#include <type_traits>
|
|
|
|
namespace xo {
|
|
namespace ast {
|
|
/** @class Constant
|
|
* @brief syntax for a literal constant.
|
|
*
|
|
* Require:
|
|
* 1. T must be a POD type (plain old data)
|
|
* We need this to be true so that we can generate
|
|
* code for constructing a T instance by memcopying
|
|
* @ref value_
|
|
*
|
|
* @tp T type of captured literal.
|
|
**/
|
|
template <typename T>
|
|
class Constant : public ConstantInterface {
|
|
public:
|
|
using Reflect = xo::reflect::Reflect;
|
|
using TaggedPtr = xo::reflect::TaggedPtr;
|
|
using TypeDescr = xo::reflect::TypeDescr;
|
|
|
|
public:
|
|
/** create constant expression representing literal value x **/
|
|
static rp<Constant> make(const T & x) {
|
|
TypeDescr x_valuetype = Reflect::require<T>();
|
|
|
|
return new Constant(x_valuetype, x);
|
|
}
|
|
|
|
const T & value() const { return value_; }
|
|
|
|
// ----- ConstantInterface -----
|
|
|
|
virtual TypeDescr value_td() const override { return value_td_; }
|
|
virtual TaggedPtr value_tp() const override {
|
|
/* note: idk why, but need to spell this out in two steps with gcc 13.2 */
|
|
const void * erased_cptr = &value_;
|
|
void * erased_ptr = const_cast<void*>(erased_cptr);
|
|
|
|
return TaggedPtr(value_td_, erased_ptr);
|
|
}
|
|
|
|
// ----- Expression -----
|
|
|
|
virtual std::size_t visit_preorder(VisitFn visitor_fn) override {
|
|
visitor_fn(this);
|
|
return 1;
|
|
}
|
|
|
|
virtual std::size_t visit_layer(VisitFn visitor_fn) override {
|
|
visitor_fn(this);
|
|
return 1;
|
|
}
|
|
|
|
virtual rp<Expression> xform_layer(TransformFn xform_fn) override {
|
|
return xform_fn(this);
|
|
}
|
|
|
|
virtual void display(std::ostream & os) const override {
|
|
os << "<Constant";
|
|
if (value_td_)
|
|
os << xtag("type", value_td_->short_name());
|
|
else
|
|
os << xtag("type", "nullptr");;
|
|
os << xtag("value", value_);
|
|
os << ">";
|
|
}
|
|
|
|
private:
|
|
explicit Constant(TypeDescr x_type, const T & x)
|
|
: ConstantInterface(exprtype::constant, x_type),
|
|
value_td_{Reflect::require<T>()},
|
|
value_(x)
|
|
{
|
|
static_assert(std::is_standard_layout_v<T> && std::is_trivial_v<T>);
|
|
}
|
|
|
|
private:
|
|
/** type description for T **/
|
|
TypeDescr value_td_;
|
|
/** value of this constant **/
|
|
T value_;
|
|
}; /*Constant*/
|
|
|
|
template <typename T>
|
|
rp<Constant<std::remove_reference_t<T>>>
|
|
make_constant(const T & x) {
|
|
return Constant<T>::make(x);
|
|
}
|
|
|
|
} /*namespace ast*/
|
|
} /*namespace xo*/
|
|
|
|
/** end Constant.hpp **/
|