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68 lines
1.6 KiB
68 lines
1.6 KiB
//
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// calc5.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 <cstdlib>
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#include <iostream>
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#include <peglib.h>
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using namespace peg;
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int main(int argc, const char **argv) {
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if (argc < 2 || std::string("--help") == argv[1]) {
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std::cout << "usage: calc5 [formula]" << std::endl;
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return 1;
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}
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std::function<long(const Ast &)> eval = [&](const Ast &ast) {
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if (ast.name == "NUMBER") {
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return ast.token_to_number<long>();
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} else {
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const auto &nodes = ast.nodes;
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auto result = eval(*nodes[0]);
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if (nodes.size() > 1) {
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auto ope = nodes[1]->token[0];
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auto num = eval(*nodes[2]);
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switch (ope) {
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case '+': result += num; break;
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case '-': result -= num; break;
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case '*': result *= num; break;
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case '/': result /= num; break;
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}
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}
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return result;
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}
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};
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parser parser(R"(
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EXPRESSION <- ATOM (OPERATOR ATOM)* {
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precedence
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L - +
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L / *
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}
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ATOM <- NUMBER / '(' EXPRESSION ')'
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OPERATOR <- < [-+/*] >
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NUMBER <- < '-'? [0-9]+ >
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%whitespace <- [ \t\r\n]*
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)");
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parser.enable_ast();
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auto expr = argv[1];
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std::shared_ptr<Ast> ast;
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if (parser.parse(expr, ast)) {
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ast = AstOptimizer(true).optimize(ast);
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std::cout << ast_to_s(ast);
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std::cout << expr << " = " << eval(*ast) << std::endl;
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return 0;
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}
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std::cout << "syntax error..." << std::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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