407 lines
7.8 KiB
C++
407 lines
7.8 KiB
C++
#include "mpw-shell.h"
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#include "fdset.h"
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#include "value.h"
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#include <unistd.h>
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#include <fcntl.h>
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/*
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* I'm sick of fighting with lemon. Just generate it by hand.
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*
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*/
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template<class T>
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T pop(std::vector<T> &v) {
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T t = std::move(v.back());
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v.pop_back();
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return t;
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}
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int open(const std::string &name, int flags) {
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// dup2 does not copy the O_CLOEXEC flag so it's safe to use.
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int fd = ::open(name.c_str(), flags | O_CLOEXEC, 0666);
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if (fd < 0) {
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std::string error = "### MPW Shell - Unable to open ";
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error.push_back('"');
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error.append(name);
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error.push_back('"');
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error.push_back('.');
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throw std::runtime_error(error);
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}
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return fd;
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}
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void parse_tokens(std::vector<token> &&tokens, process &p) {
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fdset fds;
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std::vector<std::string> argv;
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std::reverse(tokens.begin(), tokens.end());
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argv.reserve(tokens.size());
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// first token is always treated as a string.
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token t = pop(tokens);
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argv.emplace_back(std::move(t.string));
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while(!tokens.empty()) {
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t = pop(tokens);
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switch (t.type) {
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// >, >> -- redirect stdout.
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case '>':
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case '>>':
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{
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int flags;
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if (t.type == '>') flags = O_WRONLY | O_CREAT | O_TRUNC;
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else flags = O_WRONLY | O_CREAT | O_APPEND;
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if (tokens.empty()) {
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throw std::runtime_error("### MPW Shell - Missing file name.");
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}
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token name = pop(tokens);
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int fd = open(name.string, flags);
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fds.set(1, fd);
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}
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break;
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// < -- redirect stdin.
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case '<':
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{
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int flags = O_RDONLY;
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if (tokens.empty()) {
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throw std::runtime_error("### MPW Shell - Missing file name.");
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}
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token name = pop(tokens);
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int fd = open(name.string, flags);
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fds.set(0, fd);
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}
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break;
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default:
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argv.emplace_back(std::move(t.string));
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break;
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}
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}
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p.arguments = std::move(argv);
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p.fds = std::move(fds);
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}
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class expression_parser {
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public:
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expression_parser(const std::string &n, std::vector<token> &&t) :
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name(n), tokens(std::move(t))
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{}
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expression_parser(const expression_parser &) = delete;
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expression_parser(expression_parser &&) = delete;
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expression_parser& operator=(const expression_parser &) = delete;
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expression_parser& operator=(expression_parser &&) = delete;
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// returns integer value of the expression.
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int32_t evaluate();
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private:
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value terminal();
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value unary();
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value binary();
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value eval(int op, value &lhs, value &rhs);
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[[noreturn]] void expect_binary_operator();
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[[noreturn]] void end_of_expression();
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[[noreturn]] void divide_by_zero();
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int peek_type() const;
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token next();
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static int precedence(int);
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void skip() {
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if (!tokens.empty()) tokens.pop_back();
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}
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const std::string &name;
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std::vector<token> tokens;
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};
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int expression_parser::peek_type() const {
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if (tokens.empty()) return token::eof;
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return tokens.back().type;
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}
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token expression_parser::next() {
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if (tokens.empty()) return token("", token::eof); // error?
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return pop(tokens);
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}
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void expression_parser::expect_binary_operator() {
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token t = next();
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std::string error;
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error = "### " + name;
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error += " - Expected a binary operator when \"";
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error += t.string;
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error += "\" was encountered.";
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throw std::runtime_error(error);
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}
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void expression_parser::end_of_expression() {
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std::string error;
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error = "### " + name + " - Unexpected end of expression.";
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throw std::runtime_error(error);
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}
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void expression_parser::divide_by_zero() {
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std::string error;
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error = "### " + name + " - Attempt to divide by zero.";
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throw std::runtime_error(error);
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}
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value expression_parser::binary() {
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std::vector<value> output;
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std::vector<std::pair<int, int>> operators;
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value v = unary();
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output.emplace_back(std::move(v));
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for(;;) {
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// check for an operator.
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int type = peek_type();
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if (type == token::eof) break;
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if (type == ')') break;
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int p = precedence(type);
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if (!p) expect_binary_operator();
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skip();
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while (!operators.empty() && operators.back().second <= p) {
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// reduce top ops.
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int op = operators.back().first;
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operators.pop_back();
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value rhs = pop(output);
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value lhs = pop(output);
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output.emplace_back(eval(op, lhs, rhs));
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}
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operators.push_back(std::make_pair(type, p));
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v = unary();
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output.emplace_back(std::move(v));
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}
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// reduce...
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while (!operators.empty()) {
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int op = pop(operators).first;
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value rhs = pop(output);
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value lhs = pop(output);
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output.emplace_back(eval(op, lhs, rhs));
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}
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if (output.size() != 1) throw std::runtime_error("binary stack error");
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return pop(output);
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}
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int expression_parser::precedence(int op) {
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switch (op) {
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case '*':
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case '%':
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case '/':
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return 3;
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case '+':
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case '-':
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return 4;
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case '>>':
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case '<<':
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return 5;
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case '<':
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case '<=':
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case '>':
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case '>=':
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return 6;
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case '==':
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case '!=':
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case token::equivalent:
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case token::not_equivalent:
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return 7;
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case '&':
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return 8;
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case '^':
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return 9;
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case '|':
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return 10;
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case '&&':
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return 11;
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case '||':
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return 12;
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}
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return 0;
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//throw std::runtime_error("unimplemented op";);
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}
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value expression_parser::eval(int op, value &lhs, value &rhs) {
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switch (op) {
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case '*':
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return lhs.to_number() * rhs.to_number();
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case '/':
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if (!rhs.to_number()) divide_by_zero();
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return lhs.to_number() / rhs.to_number();
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case '%':
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if (!rhs.to_number()) divide_by_zero();
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return lhs.to_number() % rhs.to_number();
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case '+':
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return lhs.to_number() + rhs.to_number();
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case '-':
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return lhs.to_number() - rhs.to_number();
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case '>':
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return lhs.to_number() > rhs.to_number();
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case '<':
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return lhs.to_number() < rhs.to_number();
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case '<=':
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return lhs.to_number() <= rhs.to_number();
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case '>=':
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return lhs.to_number() >= rhs.to_number();
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case '>>':
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return lhs.to_number() >> rhs.to_number();
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case '<<':
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return lhs.to_number() >> rhs.to_number();
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// logical || . NaN ok
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case '||':
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return lhs.to_number(1) || rhs.to_number(1);
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// logical && . NaN ok
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case '&&':
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return lhs.to_number(1) && rhs.to_number(1);
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case '|':
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return lhs.to_number() | rhs.to_number();
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case '&':
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return lhs.to_number() & rhs.to_number();
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case '^':
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return lhs.to_number() ^ rhs.to_number();
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case '==':
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// string ==. 0x00==0 -> 0
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// as a special case, 0=="". go figure.
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if (lhs.string == "" && rhs.string == "0") return 1;
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if (lhs.string == "0" && rhs.string == "") return 1;
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return lhs.string == rhs.string;
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case '!=':
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if (lhs.string == "" && rhs.string == "0") return 0;
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if (lhs.string == "0" && rhs.string == "") return 0;
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return lhs.string != rhs.string;
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}
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// todo...
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throw std::runtime_error("unimplemented op");
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}
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value expression_parser::unary() {
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int type = peek_type();
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switch (type) {
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case '-':
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case '+':
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case '!':
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case '~':
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next();
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value v = unary();
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// + is a nop.. doesn't even check if it's a number.
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if (type == '-') v = -v.to_number();
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if (type == '~') v = ~v.to_number();
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if (type == '!') v = !v.to_number(1); // logical !, NaN ok.
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return v;
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}
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return terminal();
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}
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value expression_parser::terminal() {
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int type = peek_type();
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if (type == token::text) {
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token t = next();
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return value(std::move(t.string));
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}
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if (type == '(') {
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next();
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value v = binary();
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type = peek_type();
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if (type != ')') {
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end_of_expression();
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}
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next();
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return v;
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}
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// insert a fake token.
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return value();
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}
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int32_t expression_parser::evaluate() {
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if (tokens.empty()) return 0;
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value v = binary();
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if (!tokens.empty()) {
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if (tokens.back().type == ')')
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throw std::runtime_error("### MPW Shell - Extra ) command.");
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throw std::runtime_error("evaluation stack error."); // ?? should be caught above.
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}
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return v.to_number(1);
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}
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int32_t evaluate_expression(const std::string &name, std::vector<token> &&tokens) {
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expression_parser p(name, std::move(tokens));
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return p.evaluate();
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}
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