cpppeg/sample-4.cpp at master · kik/cpppeg · GitHub

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#include<iostream>
#include<string>
#include<numeric>
#include<boost/lexical_cast.hpp>
#include<boost/function.hpp>
#include"peg.hpp"

namespacefusion= boost::fusion;
usingnamespacepeg;
usingnamespacestd;

template<classT>
structt : publicT
{
voidaction(const T& t, const rep<peg::ws>&) {
 *static_cast<T*>(this) = t;
 }
};

template<char c, classT>
structop_t : publicT
{
voidaction(t<ch<c> >) {}
};

template<classT, classU>
structop_or : publicboost::function<int(int,int)>
{
typedef boost::function<int(int,int)> Base;
 op_or& operator=(const Base& x) {
 *static_cast<Base *>(this) = x;
return *this;
 }
voidaction_0(const T& t) {
 *this = t;
 }

voidaction_1(const U& u) {
 *this = u;
 }
};

typedefop_t<'+', std::plus<int> > op_plus;
typedefop_t<'-', std::minus<int> > op_minus;
typedefop_t<'*', std::multiplies<int> > op_multiplies;
typedefop_t<'/', std::divides<int> > op_divides;

structint_lit_s
{
int v;
voidaction(const replus<digit>& s) {
 v = boost::lexical_cast<int>(s);
 }
};

typedef t<int_lit_s> int_lit;

typedef t<ch<'('> > open_paren;
typedef t<ch<')'> > close_paren;

structtree;
typedef boost::shared_ptr<tree> ptree;

structtree
{
typedef ptree result_type;
virtual~tree() {}
virtualinteval() const = 0;
};

structbinary_tree : publictree
{
 boost::function<int(int,int)> op;
 ptree left;
 ptree right;
inteval() const { returnop(left->eval(), right->eval()); }
};

template<classT, classOp>
structleft_assoc_expr : publicbinary_tree
{
typedef left_assoc_expr<T, Op> self_type;
structf {
 ptree operator()(const ptree e, const fusion::vector<Op, ptr<T> >& x) {
 self_type *p = new self_type;
 p->op = fusion::at_c<0>(x);
 p->left = e;
 p->right = fusion::at_c<1>(x);
returnptree(p);
 }
 };
static ptree action(const ptr<T>& e, const rep<fusion::vector<Op, ptr<T> > >& elist) {
returnstd::accumulate(elist.begin(), elist.end(), e, f());
 }
};

structprimary_expr;

typedef left_assoc_expr<primary_expr, op_or<op_multiplies, op_divides> > multi_expr;
typedef left_assoc_expr<multi_expr, op_or<op_plus, op_minus> > expr;

structprimary_expr : publictree
{
int v;
inteval() const { return v; }
static ptree action_0(int_lit lit) {
 primary_expr *p = new primary_expr;
 p->v = lit.v;
returnptree(p);
 }

static ptree action_1(open_paren, const ptr<expr>& e, close_paren) {
return e;
 }
};

voidtest(const string& s)
{
 cout << s << " ---> ";
 parser<ptr<expr> > parser;
 ptr<expr> e;

if (!parser.parse(e, s.begin(), s.end())) {
 cout << "parse error" << endl;
 } else {
 cout << e->eval() << endl;
 }

}

intmain()
{
test("1");
test("42");
test("10 + 13");
test("10 + 20 * 3");
test("(2 + 4) * (5 - 2)");
test("2 * 4 / 8");
return0;
}