[et] lambda/curry
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77e5f927e7
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13983f9a6e
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#include <cstdio>
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#include <tuple>
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/* **** */
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/* tags */
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namespace tag {
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struct Argument;
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struct Add;
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struct Mul;
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struct Minus;
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}
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/* ********** */
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/* expression */
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template<typename Op, typename... Operands>
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struct Expr {
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std::tuple<Operands...> operands;
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Expr(Operands... operands): operands{operands...} {}
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};
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template<std::size_t I>
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struct Argument {};
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namespace arg {
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Argument<0> _0;
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Argument<1> _1;
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Argument<2> _2;
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Argument<3> _3;
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// ...
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}
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/* *********** */
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/* type traits */
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namespace impl {
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template<typename T> struct IsExpr: std::false_type {};
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template<typename Op, typename... Operands>
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struct IsExpr<Expr<Op, Operands...>>: std::true_type {};
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template<std::size_t I>
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struct IsExpr<Argument<I>>: std::true_type {};
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}
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template<typename T>
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constexpr bool IsExpr = impl::IsExpr<T>::value;
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template<
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typename LHS, typename RHS,
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std::enable_if_t<IsExpr<LHS> && IsExpr<RHS>>* = nullptr
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>
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auto operator+(LHS lhs, RHS rhs) {
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return Expr<tag::Add, LHS, RHS>{lhs, rhs};
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}
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template<
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typename LHS, typename RHS,
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std::enable_if_t<IsExpr<LHS> && IsExpr<RHS>>* = nullptr
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>
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auto operator*(LHS lhs, RHS rhs) {
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return Expr<tag::Mul, LHS, RHS>{lhs, rhs};
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}
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template<
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typename RHS,
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std::enable_if_t<IsExpr<RHS>>* = nullptr
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>
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auto operator-(RHS rhs) {
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return Expr<tag::Minus, RHS>{rhs};
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}
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/* ********** */
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/* evaluators */
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template<typename> struct EvaluatorElem;
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template<>
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struct EvaluatorElem<tag::Argument> {
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template<typename T>
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static auto eval(T value) { return value; }
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};
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template<>
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struct EvaluatorElem<tag::Add> {
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template<typename T>
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static auto eval(T lhs, T rhs) { return lhs + rhs; }
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};
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template<>
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struct EvaluatorElem<tag::Mul> {
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template<typename T>
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static auto eval(T lhs, T rhs) { return lhs * rhs; }
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};
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template<>
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struct EvaluatorElem<tag::Minus> {
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template<typename T>
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static auto eval(T rhs) { return -rhs; }
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};
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/* *** */
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namespace impl {
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template<typename> struct GetExprOp;
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template<typename Op, typename... Operands>
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struct GetExprOp<Expr<Op, Operands...>> {
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using type = Op;
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};
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}
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template<typename E>
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using GetExprOp = typename impl::GetExprOp<E>::type;
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namespace impl {
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template<typename...> struct MaxArgument;
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template<typename Argument, typename... Arguments>
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struct MaxArgument<Argument, Arguments...>:
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std::integral_constant<std::size_t, MaxArgument<Arguments...>::value> {};
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template<std::size_t I, typename... Arguments>
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struct MaxArgument<Argument<I>, Arguments...> {
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static constexpr std::size_t M = MaxArgument<Arguments...>::value;
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static constexpr std::size_t value = I>M? I:M;
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};
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template<typename Op, typename... Operands, typename... Arguments>
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struct MaxArgument<Expr<Op, Operands...>, Arguments...> {
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static constexpr std::size_t M0 = MaxArgument<Arguments...>::value;
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static constexpr std::size_t M1 = MaxArgument<Operands...>::value;
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static constexpr std::size_t value = M0>M1? M0:M1;
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};
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template<> struct MaxArgument<>: std::integral_constant<std::size_t, 0> {};
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}
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template<typename... Arguments>
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constexpr std::size_t MaxArgument = impl::MaxArgument<Arguments...>::value;
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template<typename Expression, template<typename> class EvaluatorTemplate, typename BoundArgs = std::tuple<>, bool Impl = false>
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struct Evaluable {
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using Evaluator = EvaluatorTemplate<GetExprOp<Expression>>;
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Expression expr;
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BoundArgs boundArgs;
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static constexpr std::size_t arity = MaxArgument<Expression> + 1 - std::tuple_size<BoundArgs>{};
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template<typename... Arguments, std::enable_if_t<sizeof...(Arguments) >= arity>* = nullptr>
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auto operator()(Arguments... arguments) {
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static_assert(Impl || sizeof...(Arguments) <= arity, "too many arguments");
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using IndexSequence = std::make_index_sequence<std::tuple_size<BoundArgs>{}>;
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return evalBound(IndexSequence{}, arguments...);
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}
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template<typename... Arguments, std::enable_if_t<(sizeof...(Arguments) < arity)>* = nullptr>
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auto operator()(Arguments... arguments) {
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auto newBoundArgs = std::tuple_cat(boundArgs, std::make_tuple(arguments...));
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return Evaluable<Expression, EvaluatorTemplate, decltype(newBoundArgs)>{expr, newBoundArgs};
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}
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private:
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template<std::size_t... Is, typename... Arguments>
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auto evalBound(std::index_sequence<Is...>, Arguments... arguments) {
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using IndexSequence = std::make_index_sequence<std::tuple_size<decltype(expr.operands)>{}>;
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return eval(IndexSequence{}, std::get<Is>(boundArgs)..., arguments...);
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}
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template<typename... Arguments, std::size_t... Is>
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auto eval(std::index_sequence<Is...>, Arguments... arguments) {
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using IndexSequence = std::index_sequence<Is...>;
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return Evaluator::eval(std::get<Is>(resolveOperands(IndexSequence{}, expr.operands, arguments...))...);
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}
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template<std::size_t... Is, typename T, typename... Arguments>
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auto resolveOperands(std::index_sequence<Is...>, T tuple, Arguments... arguments) {
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return std::make_tuple(resolveOperand(std::get<Is>(tuple), arguments...)...);
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}
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template<std::size_t I, typename... Arguments>
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auto resolveOperand(Argument<I>, Arguments... arguments) {
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return std::get<I>(std::make_tuple(arguments...));
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}
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template<typename... Ts, typename... Arguments>
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auto resolveOperand(Expr<Ts...> expr, Arguments... arguments) {
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return Evaluable<Expr<Ts...>, EvaluatorTemplate, std::tuple<>, true>{expr, {}}(arguments...);
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}
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};
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template<template<typename> class Evaluator, typename Expr>
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auto bind(Expr expr) {
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return Evaluable<Expr, Evaluator>{expr, {}};
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}
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int main() {
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int volatile v0 = 3, v1 = 5, v2 = 7, v3 = 9;
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int result;
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using namespace arg;
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auto expr = _1 * -(_2 + _0) + _3 * _0;
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auto fElem = bind<EvaluatorElem>(expr);
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auto fCurry = fElem(v0);
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result = fCurry(v1)(v2)(v3);
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std::printf("result: %d\n", result);
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}
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#include <algorithm>
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#include <cstdio>
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#include <tuple>
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#include <vector>
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/* **** */
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/* tags */
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namespace tag {
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struct Argument;
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struct Add;
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struct Mul;
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struct Minus;
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struct Less;
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}
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/* ********** */
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/* expression */
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template<typename Op, typename... Operands>
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struct Expr {
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std::tuple<Operands...> operands;
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Expr(Operands... operands): operands{operands...} {}
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};
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template<std::size_t I>
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struct Argument {};
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namespace arg {
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Argument<0> _0;
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Argument<1> _1;
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Argument<2> _2;
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Argument<3> _3;
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// ...
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}
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/* *********** */
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/* type traits */
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namespace impl {
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template<typename T> struct IsExpr: std::false_type {};
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template<typename Op, typename... Operands>
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struct IsExpr<Expr<Op, Operands...>>: std::true_type {};
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template<std::size_t I>
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struct IsExpr<Argument<I>>: std::true_type {};
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}
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template<typename T>
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constexpr bool IsExpr = impl::IsExpr<T>::value;
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template<
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typename LHS, typename RHS,
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std::enable_if_t<IsExpr<LHS> && IsExpr<RHS>>* = nullptr
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>
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auto operator+(LHS lhs, RHS rhs) {
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return Expr<tag::Add, LHS, RHS>{lhs, rhs};
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}
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template<
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typename LHS, typename RHS,
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std::enable_if_t<IsExpr<LHS> && IsExpr<RHS>>* = nullptr
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>
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auto operator*(LHS lhs, RHS rhs) {
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return Expr<tag::Mul, LHS, RHS>{lhs, rhs};
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}
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template<
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typename RHS,
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std::enable_if_t<IsExpr<RHS>>* = nullptr
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>
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auto operator-(RHS rhs) {
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return Expr<tag::Minus, RHS>{rhs};
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}
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template<
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typename LHS, typename RHS,
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std::enable_if_t<IsExpr<LHS> && IsExpr<RHS>>* = nullptr
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>
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auto operator<(LHS lhs, RHS rhs) {
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return Expr<tag::Less, LHS, RHS>{lhs, rhs};
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}
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/* ********** */
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/* evaluators */
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template<typename> struct EvaluatorElem;
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template<>
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struct EvaluatorElem<tag::Argument> {
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template<typename T>
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static auto eval(T value) { return value; }
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};
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template<>
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struct EvaluatorElem<tag::Add> {
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template<typename T>
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static auto eval(T lhs, T rhs) { return lhs + rhs; }
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};
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template<>
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struct EvaluatorElem<tag::Mul> {
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template<typename T>
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static auto eval(T lhs, T rhs) { return lhs * rhs; }
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};
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template<>
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struct EvaluatorElem<tag::Minus> {
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template<typename T>
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static auto eval(T rhs) { return -rhs; }
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};
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template<>
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struct EvaluatorElem<tag::Less> {
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template<typename T>
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static auto eval(T lhs, T rhs) { return lhs < rhs; }
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};
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/* *** */
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namespace impl {
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template<typename> struct GetExprOp;
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template<typename Op, typename... Operands>
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struct GetExprOp<Expr<Op, Operands...>> {
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using type = Op;
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};
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}
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template<typename E>
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using GetExprOp = typename impl::GetExprOp<E>::type;
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namespace impl {
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template<typename...> struct MaxArgument;
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template<typename Argument, typename... Arguments>
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struct MaxArgument<Argument, Arguments...>:
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std::integral_constant<std::size_t, MaxArgument<Arguments...>::value> {};
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template<std::size_t I, typename... Arguments>
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struct MaxArgument<Argument<I>, Arguments...> {
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static constexpr std::size_t M = MaxArgument<Arguments...>::value;
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static constexpr std::size_t value = I>M? I:M;
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};
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template<typename Op, typename... Operands, typename... Arguments>
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struct MaxArgument<Expr<Op, Operands...>, Arguments...> {
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static constexpr std::size_t M0 = MaxArgument<Arguments...>::value;
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static constexpr std::size_t M1 = MaxArgument<Operands...>::value;
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static constexpr std::size_t value = M0>M1? M0:M1;
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};
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template<> struct MaxArgument<>: std::integral_constant<std::size_t, 0> {};
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}
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template<typename... Arguments>
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constexpr std::size_t MaxArgument = impl::MaxArgument<Arguments...>::value;
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template<typename Expression, template<typename> class EvaluatorTemplate, bool Impl = false>
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struct Evaluable {
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using Evaluator = EvaluatorTemplate<GetExprOp<Expression>>;
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Expression expr;
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static constexpr std::size_t arity = MaxArgument<Expression> + 1;
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template<typename... Arguments, std::enable_if_t<(sizeof...(Arguments) >= arity)>* = nullptr>
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auto operator()(Arguments... arguments) {
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static_assert(Impl || sizeof...(Arguments) <= arity, "too many arguments");
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using IndexSequence = std::make_index_sequence<std::tuple_size<decltype(expr.operands)>{}>;
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return eval(IndexSequence{}, arguments...);
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}
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template<typename... Arguments, std::enable_if_t<(sizeof...(Arguments) < arity)>* = nullptr>
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auto operator()(Arguments...) {
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static_assert(sizeof...(Arguments) >= arity, "too few arguments");
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}
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private:
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template<typename... Arguments, std::size_t... Is>
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auto eval(std::index_sequence<Is...>, Arguments... arguments) {
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using IndexSequence = std::index_sequence<Is...>;
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return Evaluator::eval(std::get<Is>(resolveOperands(IndexSequence{}, expr.operands, arguments...))...);
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}
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template<std::size_t... Is, typename T, typename... Arguments>
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auto resolveOperands(std::index_sequence<Is...>, T tuple, Arguments... arguments) {
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return std::make_tuple(resolveOperand(std::get<Is>(tuple), arguments...)...);
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}
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template<std::size_t I, typename... Arguments>
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auto resolveOperand(Argument<I>, Arguments... arguments) {
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return std::get<I>(std::make_tuple(arguments...));
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}
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template<typename... Ts, typename... Arguments>
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auto resolveOperand(Expr<Ts...> expr, Arguments... arguments) {
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return Evaluable<Expr<Ts...>, EvaluatorTemplate, true>{expr}(arguments...);
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}
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};
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template<template<typename> class Evaluator, typename Expr>
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auto bind(Expr expr) {
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return Evaluable<Expr, Evaluator>{expr};
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}
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/* ******** */
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/* examples */
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void directCall() {
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using namespace arg;
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int volatile v0 = 3, v1 = 5, v2 = 7, v3 = 9;
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int result;
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auto expr = _1 * -(_2 + _0) + _3 * _0;
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auto fElem = bind<EvaluatorElem>(expr);
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result = fElem(v0, v1, v2, v3);
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std::printf("result: %d\n", result);
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}
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void lambda() {
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using namespace arg;
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std::vector<int> v{5, 7, 3, 1, 6, 9, 4, 2};
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std::vector<int> w(v.size());
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std::sort(std::begin(v), std::end(v), bind<EvaluatorElem>(_1 < _0));
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std::transform(std::begin(v), std::begin(w), std::begin(w), bind<EvaluatorElem>(_0 * _0));
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for(auto i: v) std::printf("%d ", i);
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std::puts("");
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for(auto i: w) std::printf("%d ", i);
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std::puts("");
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}
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int main() {
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directCall();
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lambda();
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}
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