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carbon-lang/executable_semantics/interpreter/action.h
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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#ifndef EXECUTABLE_SEMANTICS_INTERPRETER_ACTION_H_
#define EXECUTABLE_SEMANTICS_INTERPRETER_ACTION_H_
#include <vector>
#include "common/ostream.h"
#include "executable_semantics/ast/expression.h"
#include "executable_semantics/ast/statement.h"
#include "executable_semantics/interpreter/stack.h"
#include "executable_semantics/interpreter/value.h"
namespace Carbon {
enum class ActionKind {
LValAction,
ExpressionAction,
StatementAction,
ValAction,
};
struct LValAction {
static constexpr ActionKind Kind = ActionKind::LValAction;
const Expression* exp;
};
struct ExpressionAction {
static constexpr ActionKind Kind = ActionKind::ExpressionAction;
const Expression* exp;
};
struct StatementAction {
static constexpr ActionKind Kind = ActionKind::StatementAction;
const Statement* stmt;
};
struct ValAction {
static constexpr ActionKind Kind = ActionKind::ValAction;
const Value* val;
};
struct Action {
static auto MakeLValAction(const Expression* e) -> Action*;
static auto MakeExpressionAction(const Expression* e) -> Action*;
static auto MakeStatementAction(const Statement* s) -> Action*;
static auto MakeValAction(const Value* v) -> Action*;
static void PrintList(const Stack<Action*>& ls, llvm::raw_ostream& out);
auto GetLValAction() const -> const LValAction&;
auto GetExpressionAction() const -> const ExpressionAction&;
auto GetStatementAction() const -> const StatementAction&;
auto GetValAction() const -> const ValAction&;
void Print(llvm::raw_ostream& out) const;
inline auto tag() const -> ActionKind {
return std::visit([](const auto& t) { return t.Kind; }, value);
}
// The position or state of the action. Starts at 0 and goes up to the number
// of subexpressions.
//
// pos indicates how many of the entries in the following `results` vector
// will be filled in the next time this action is active.
// For each i < pos, results[i] contains a pointer to a Value.
int pos = 0;
// Results from a subexpression.
std::vector<const Value*> results;
private:
std::variant<LValAction, ExpressionAction, StatementAction, ValAction> value;
};
} // namespace Carbon
#endif // EXECUTABLE_SEMANTICS_INTERPRETER_ACTION_H_