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115 lines
3.1 KiB
115 lines
3.1 KiB
//
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// calc3.cc
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//
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// Copyright (c) 2015 Yuji Hirose. All rights reserved.
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// MIT License
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//
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#include <peglib.h>
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#include <iostream>
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#include <cstdlib>
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using namespace peglib;
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using namespace std;
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template <typename T, typename U, typename F>
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static U reduce(T i, T end, U val, F f) {
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if (i == end) {
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return val;
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}
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tie(val, i) = f(val, i);
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return reduce(i, end, val, f);
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};
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struct ast_node
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{
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virtual ~ast_node() = default;
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virtual long eval() = 0;
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};
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struct ast_ope : public ast_node
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{
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ast_ope(char ope, shared_ptr<ast_node> left, shared_ptr<ast_node> right)
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: ope_(ope), left_(left), right_(right) {}
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long eval() override {
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switch (ope_) {
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case '+': return left_->eval() + right_->eval();
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case '-': return left_->eval() - right_->eval();
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case '*': return left_->eval() * right_->eval();
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case '/': return left_->eval() / right_->eval();
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}
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assert(false);
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return 0;
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};
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static shared_ptr<ast_node> create(const SemanticValues& sv) {
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assert(!sv.empty());
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return reduce(
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sv.begin() + 1,
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sv.end(),
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sv[0].get<shared_ptr<ast_node>>(),
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[](shared_ptr<ast_node> r, SemanticValues::const_iterator i) {
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auto ope = (i++)->val.get<char>();
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auto nd = (i++)->val.get<shared_ptr<ast_node>>();
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r = make_shared<ast_ope>(ope, r, nd);
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return make_tuple(r, i);
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});
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}
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private:
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char ope_;
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shared_ptr<ast_node> left_;
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shared_ptr<ast_node> right_;
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};
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struct ast_num : public ast_node
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{
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ast_num(long num) : num_(num) {}
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long eval() override { return num_; };
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static shared_ptr<ast_node> create(const char* s, size_t n) {
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return make_shared<ast_num>(atol(s));
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}
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private:
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long num_;
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};
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int main(int argc, const char** argv)
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{
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if (argc < 2 || string("--help") == argv[1]) {
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cout << "usage: calc3 [formula]" << endl;
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return 1;
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}
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peg parser(
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" EXPRESSION <- _ TERM (TERM_OPERATOR TERM)* "
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" TERM <- FACTOR (FACTOR_OPERATOR FACTOR)* "
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" FACTOR <- NUMBER / '(' _ EXPRESSION ')' _ "
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" TERM_OPERATOR <- < [-+] > _ "
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" FACTOR_OPERATOR <- < [/*] > _ "
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" NUMBER <- < [0-9]+ > _ "
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" ~_ <- [ \t\r\n]* "
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);
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parser["EXPRESSION"] = ast_ope::create;
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parser["TERM"] = ast_ope::create;
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parser["TERM_OPERATOR"] = [](const char* s, size_t n) { return *s; };
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parser["FACTOR_OPERATOR"] = [](const char* s, size_t n) { return *s; };
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parser["NUMBER"] = ast_num::create;
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auto expr = argv[1];
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shared_ptr<ast_node> ast;
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if (parser.parse(expr, ast)) {
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cout << expr << " = " << ast->eval() << endl;
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return 0;
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}
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cout << "syntax error..." << endl;
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return -1;
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}
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// vim: et ts=4 sw=4 cin cino={1s ff=unix
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