You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
455 lines
15 KiB
455 lines
15 KiB
//
|
|
// pl0.cc - PL/0 interpreter (https://en.wikipedia.org/wiki/PL/0)
|
|
//
|
|
// Copyright (c) 2015 Yuji Hirose. All rights reserved.
|
|
// MIT License
|
|
//
|
|
|
|
#include <peglib.h>
|
|
#include <fstream>
|
|
#include <iostream>
|
|
#include <sstream>
|
|
|
|
using namespace peg;
|
|
using namespace std;
|
|
|
|
/*
|
|
* PEG Grammar
|
|
*/
|
|
auto grammar = R"(
|
|
program <- _ block '.' _
|
|
|
|
block <- const var procedure statement
|
|
const <- ('CONST' __ ident '=' _ number (',' _ ident '=' _ number)* ';' _)?
|
|
var <- ('VAR' __ ident (',' _ ident)* ';' _)?
|
|
procedure <- ('PROCEDURE' __ ident ';' _ block ';' _)*
|
|
|
|
statement <- (assignment / call / statements / if / while / out / in)?
|
|
assignment <- ident ':=' _ expression
|
|
call <- 'CALL' __ ident
|
|
statements <- 'BEGIN' __ statement (';' _ statement )* 'END' __
|
|
if <- 'IF' __ condition 'THEN' __ statement
|
|
while <- 'WHILE' __ condition 'DO' __ statement
|
|
out <- ('out' __ / 'write' __ / '!' _) expression
|
|
in <- ('in' __ / 'read' __ / '?' _) ident
|
|
|
|
condition <- odd / compare
|
|
odd <- 'ODD' __ expression
|
|
compare <- expression compare_op expression
|
|
compare_op <- < '=' / '#' / '<=' / '<' / '>=' / '>' > _
|
|
|
|
expression <- sign term (term_op term)*
|
|
sign <- < [-+]? > _
|
|
term_op <- < [-+] > _
|
|
|
|
term <- factor (factor_op factor)*
|
|
factor_op <- < [*/] > _
|
|
|
|
factor <- ident / number / '(' _ expression ')' _
|
|
|
|
ident <- < [a-z] [a-z0-9]* > _
|
|
number <- < [0-9]+ > _
|
|
|
|
~_ <- [ \t\r\n]*
|
|
~__ <- ![a-z0-9_] _
|
|
)";
|
|
|
|
/*
|
|
* Utilities
|
|
*/
|
|
string format_error_message(const string& path, size_t ln, size_t col, const string& msg) {
|
|
stringstream ss;
|
|
ss << path << ":" << ln << ":" << col << ": " << msg << endl;
|
|
return ss.str();
|
|
}
|
|
|
|
/*
|
|
* Ast
|
|
*/
|
|
struct SymbolScope;
|
|
|
|
struct Annotation
|
|
{
|
|
shared_ptr<SymbolScope> scope;
|
|
};
|
|
|
|
typedef AstBase<Annotation> AstPL0;
|
|
|
|
/*
|
|
* Symbol Table
|
|
*/
|
|
struct SymbolScope
|
|
{
|
|
SymbolScope(shared_ptr<SymbolScope> outer) : outer(outer) {}
|
|
|
|
bool has_symbol(const string& ident) const {
|
|
auto ret = constants.count(ident) || variables.count(ident);
|
|
return ret ? true : (outer ? outer->has_symbol(ident) : false);
|
|
}
|
|
|
|
bool has_constant(const string& ident) const {
|
|
return constants.count(ident) ? true : (outer ? outer->has_constant(ident) : false);
|
|
}
|
|
|
|
bool has_variable(const string& ident) const {
|
|
return variables.count(ident) ? true : (outer ? outer->has_variable(ident) : false);
|
|
}
|
|
|
|
bool has_procedure(const string& ident) const {
|
|
return procedures.count(ident) ? true : (outer ? outer->has_procedure(ident) : false);
|
|
}
|
|
|
|
map<string, int> constants;
|
|
set<string> variables;
|
|
map<string, shared_ptr<AstPL0>> procedures;
|
|
|
|
private:
|
|
shared_ptr<SymbolScope> outer;
|
|
};
|
|
|
|
void throw_runtime_error(const shared_ptr<AstPL0> node, const string& msg) {
|
|
throw runtime_error(format_error_message(node->path, node->line, node->column, msg));
|
|
}
|
|
|
|
struct SymbolTable
|
|
{
|
|
static void build_on_ast(const shared_ptr<AstPL0> ast, shared_ptr<SymbolScope> scope = nullptr) {
|
|
switch (ast->tag) {
|
|
case "block"_: block(ast, scope); break;
|
|
case "assignment"_: assignment(ast, scope); break;
|
|
case "call"_: call(ast, scope); break;
|
|
case "ident"_: ident(ast, scope); break;
|
|
default: for (auto node: ast->nodes) { build_on_ast(node, scope); } break;
|
|
}
|
|
}
|
|
|
|
private:
|
|
static void block(const shared_ptr<AstPL0> ast, shared_ptr<SymbolScope> outer) {
|
|
// block <- const var procedure statement
|
|
auto scope = make_shared<SymbolScope>(outer);
|
|
const auto& nodes = ast->nodes;
|
|
constants(nodes[0], scope);
|
|
variables(nodes[1], scope);
|
|
procedures(nodes[2], scope);
|
|
build_on_ast(nodes[3], scope);
|
|
ast->scope = scope;
|
|
}
|
|
|
|
static void constants(const shared_ptr<AstPL0> ast, shared_ptr<SymbolScope> scope) {
|
|
// const <- ('CONST' __ ident '=' _ number(',' _ ident '=' _ number)* ';' _) ?
|
|
const auto& nodes = ast->nodes;
|
|
for (auto i = 0u; i < nodes.size(); i += 2) {
|
|
const auto& ident = nodes[i + 0]->token;
|
|
if (scope->has_symbol(ident)) {
|
|
throw_runtime_error(nodes[i], "'" + ident + "' is already defined...");
|
|
}
|
|
auto number = stoi(nodes[i + 1]->token);
|
|
scope->constants.emplace(ident, number);
|
|
}
|
|
}
|
|
|
|
static void variables(const shared_ptr<AstPL0> ast, shared_ptr<SymbolScope> scope) {
|
|
// var <- ('VAR' __ ident(',' _ ident)* ';' _) ?
|
|
const auto& nodes = ast->nodes;
|
|
for (auto i = 0u; i < nodes.size(); i += 1) {
|
|
const auto& ident = nodes[i]->token;
|
|
if (scope->has_symbol(ident)) {
|
|
throw_runtime_error(nodes[i], "'" + ident + "' is already defined...");
|
|
}
|
|
scope->variables.emplace(ident);
|
|
}
|
|
}
|
|
|
|
static void procedures(const shared_ptr<AstPL0> ast, shared_ptr<SymbolScope> scope) {
|
|
// procedure <- ('PROCEDURE' __ ident ';' _ block ';' _)*
|
|
const auto& nodes = ast->nodes;
|
|
for (auto i = 0u; i < nodes.size(); i += 2) {
|
|
const auto& ident = nodes[i + 0]->token;
|
|
auto block = nodes[i + 1];
|
|
scope->procedures[ident] = block;
|
|
build_on_ast(block, scope);
|
|
}
|
|
}
|
|
|
|
static void assignment(const shared_ptr<AstPL0> ast, shared_ptr<SymbolScope> scope) {
|
|
// assignment <- ident ':=' _ expression
|
|
const auto& ident = ast->nodes[0]->token;
|
|
if (scope->has_constant(ident)) {
|
|
throw_runtime_error(ast->nodes[0], "cannot modify constant value '" + ident + "'...");
|
|
} else if (!scope->has_variable(ident)) {
|
|
throw_runtime_error(ast->nodes[0], "undefined variable '" + ident + "'...");
|
|
}
|
|
}
|
|
|
|
static void call(const shared_ptr<AstPL0> ast, shared_ptr<SymbolScope> scope) {
|
|
// call <- 'CALL' __ ident
|
|
const auto& ident = ast->nodes[0]->token;
|
|
if (!scope->has_procedure(ident)) {
|
|
throw_runtime_error(ast->nodes[0], "undefined procedure '" + ident + "'...");
|
|
}
|
|
}
|
|
|
|
static void ident(const shared_ptr<AstPL0> ast, shared_ptr<SymbolScope> scope) {
|
|
const auto& ident = ast->token;
|
|
if (!scope->has_symbol(ident)) {
|
|
throw_runtime_error(ast, "undefined variable '" + ident + "'...");
|
|
}
|
|
}
|
|
};
|
|
|
|
/*
|
|
* Environment
|
|
*/
|
|
struct Environment
|
|
{
|
|
Environment(shared_ptr<SymbolScope> scope, shared_ptr<Environment> outer)
|
|
: scope(scope), outer(outer) {}
|
|
|
|
int get_value(const string& ident) const {
|
|
auto it = scope->constants.find(ident);
|
|
if (it != scope->constants.end()) {
|
|
return it->second;
|
|
} else if (scope->variables.count(ident)) {
|
|
return variables.at(ident);
|
|
}
|
|
return outer->get_value(ident);
|
|
}
|
|
|
|
void set_variable(const string& ident, int val) {
|
|
if (scope->variables.count(ident)) {
|
|
variables[ident] = val;
|
|
} else {
|
|
outer->set_variable(ident, val);
|
|
}
|
|
}
|
|
|
|
shared_ptr<AstPL0> get_procedure(const string& ident) const {
|
|
auto it = scope->procedures.find(ident);
|
|
return it != scope->procedures.end() ? it->second : outer->get_procedure(ident);
|
|
}
|
|
|
|
private:
|
|
shared_ptr<SymbolScope> scope;
|
|
shared_ptr<Environment> outer;
|
|
map<string, int> variables;
|
|
};
|
|
|
|
/*
|
|
* Interpreter
|
|
*/
|
|
struct Interpreter
|
|
{
|
|
static void exec(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env = nullptr) {
|
|
switch (ast->tag) {
|
|
case "block"_: exec_block(ast, env); break;
|
|
case "statement"_: exec_statement(ast, env); break;
|
|
case "assignment"_: exec_assignment(ast, env); break;
|
|
case "call"_: exec_call(ast, env); break;
|
|
case "statements"_: exec_statements(ast, env); break;
|
|
case "if"_: exec_if(ast, env); break;
|
|
case "while"_: exec_while(ast, env); break;
|
|
case "out"_: exec_out(ast, env); break;
|
|
case "in"_: exec_in(ast, env); break;
|
|
default: exec(ast->nodes[0], env); break;
|
|
}
|
|
}
|
|
|
|
private:
|
|
static void exec_block(const shared_ptr<AstPL0> ast, shared_ptr<Environment> outer) {
|
|
// block <- const var procedure statement
|
|
exec(ast->nodes[3], make_shared<Environment>(ast->scope, outer));
|
|
}
|
|
|
|
static void exec_statement(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// statement <- (assignment / call / statements / if / while / out / in)?
|
|
if (!ast->nodes.empty()) {
|
|
exec(ast->nodes[0], env);
|
|
}
|
|
}
|
|
|
|
static void exec_assignment(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// assignment <- ident ':=' _ expression
|
|
env->set_variable(ast->nodes[0]->token, eval(ast->nodes[1], env));
|
|
}
|
|
|
|
static void exec_call(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// call <- 'CALL' __ ident
|
|
exec_block(env->get_procedure(ast->nodes[0]->token), env);
|
|
}
|
|
|
|
static void exec_statements(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// statements <- 'BEGIN' __ statement (';' _ statement )* 'END' __
|
|
for (auto stmt: ast->nodes) {
|
|
exec(stmt, env);
|
|
}
|
|
}
|
|
|
|
static void exec_if(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// if <- 'IF' __ condition 'THEN' __ statement
|
|
if (eval_condition(ast->nodes[0], env)) {
|
|
exec(ast->nodes[1], env);
|
|
}
|
|
}
|
|
|
|
static void exec_while(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// while <- 'WHILE' __ condition 'DO' __ statement
|
|
auto cond = ast->nodes[0];
|
|
auto stmt = ast->nodes[1];
|
|
while (eval_condition(cond, env)) {
|
|
exec(stmt, env);
|
|
}
|
|
}
|
|
|
|
static void exec_out(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// out <- ('out' __ / 'write' __ / '!' _) expression
|
|
cout << eval(ast->nodes[0], env) << endl;
|
|
}
|
|
|
|
static void exec_in(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// in <- ('in' __ / 'read' __ / '?' _) ident
|
|
int val;
|
|
cin >> val;
|
|
env->set_variable(ast->nodes[0]->token, val);
|
|
}
|
|
|
|
static bool eval_condition(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// condition <- odd / compare
|
|
const auto& node = ast->nodes[0];
|
|
switch (node->tag) {
|
|
case "odd"_: return eval_odd(node, env);
|
|
case "compare"_: return eval_compare(node, env);
|
|
default: throw logic_error("invalid AstPL0 type");
|
|
}
|
|
}
|
|
|
|
static bool eval_odd(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// odd <- 'ODD' __ expression
|
|
return eval_expression(ast->nodes[0], env) != 0;
|
|
}
|
|
|
|
static bool eval_compare(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// compare <- expression compare_op expression
|
|
const auto& nodes = ast->nodes;
|
|
auto lval = eval_expression(nodes[0], env);
|
|
auto op = peg::str2tag(nodes[1]->token.c_str());
|
|
auto rval = eval_expression(nodes[2], env);
|
|
switch (op) {
|
|
case "="_: return lval == rval;
|
|
case "#"_: return lval != rval;
|
|
case "<="_: return lval <= rval;
|
|
case "<"_: return lval < rval;
|
|
case ">="_: return lval >= rval;
|
|
case ">"_: return lval > rval;
|
|
default: throw logic_error("invalid operator");
|
|
}
|
|
}
|
|
|
|
static int eval(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
switch (ast->tag) {
|
|
case "expression"_: return eval_expression(ast, env);
|
|
case "term"_: return eval_term(ast, env);
|
|
case "ident"_: return eval_ident(ast, env);
|
|
case "number"_: return eval_number(ast, env);
|
|
default: return eval(ast->nodes[0], env);
|
|
}
|
|
}
|
|
|
|
static int eval_expression(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// expression <- sign term (term_op term)*
|
|
const auto& nodes = ast->nodes;
|
|
auto sign = nodes[0]->token;
|
|
auto sign_val = (sign.empty() || sign == "+") ? 1 : -1;
|
|
auto val = eval(nodes[1], env) * sign_val;
|
|
for (auto i = 2u; i < nodes.size(); i += 2) {
|
|
auto ope = nodes[i + 0]->token[0];
|
|
auto rval = eval(nodes[i + 1], env);
|
|
switch (ope) {
|
|
case '+': val = val + rval; break;
|
|
case '-': val = val - rval; break;
|
|
}
|
|
}
|
|
return val;
|
|
}
|
|
|
|
static int eval_term(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
// term <- factor (factor_op factor)*
|
|
const auto& nodes = ast->nodes;
|
|
auto val = eval(nodes[0], env);
|
|
for (auto i = 1u; i < nodes.size(); i += 2) {
|
|
auto ope = nodes[i + 0]->token[0];
|
|
auto rval = eval(nodes[i + 1], env);
|
|
switch (ope) {
|
|
case '*':
|
|
val = val * rval;
|
|
break;
|
|
case '/':
|
|
if (rval == 0) {
|
|
throw_runtime_error(ast, "divide by 0 error");
|
|
}
|
|
val = val / rval;
|
|
break;
|
|
}
|
|
}
|
|
return val;
|
|
}
|
|
|
|
static int eval_ident(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
return env->get_value(ast->token);
|
|
}
|
|
|
|
static int eval_number(const shared_ptr<AstPL0> ast, shared_ptr<Environment> env) {
|
|
return stol(ast->token);
|
|
}
|
|
};
|
|
|
|
/*
|
|
* Main
|
|
*/
|
|
int main(int argc, const char** argv)
|
|
{
|
|
if (argc < 2) {
|
|
cout << "usage: pl0 PATH [--ast]" << endl;
|
|
return 1;
|
|
}
|
|
|
|
// Read a source file into memory
|
|
auto path = argv[1];
|
|
vector<char> source;
|
|
|
|
ifstream ifs(path, ios::in | ios::binary);
|
|
if (ifs.fail()) {
|
|
cerr << "can't open the source file." << endl;
|
|
return -1;
|
|
}
|
|
source.resize(static_cast<unsigned int>(ifs.seekg(0, ios::end).tellg()));
|
|
if (!source.empty()) {
|
|
ifs.seekg(0, ios::beg).read(&source[0], static_cast<streamsize>(source.size()));
|
|
}
|
|
|
|
// Setup a PEG parser
|
|
parser parser(grammar);
|
|
parser.enable_ast<AstPL0>();
|
|
parser.log = [&](size_t ln, size_t col, const string& msg) {
|
|
cerr << format_error_message(path, ln, col, msg) << endl;
|
|
};
|
|
|
|
// Parse the source and make an AST
|
|
shared_ptr<AstPL0> ast;
|
|
if (parser.parse_n(source.data(), source.size(), ast, path)) {
|
|
if (argc > 2 && string("--ast") == argv[2]) {
|
|
print_ast(ast);
|
|
}
|
|
try {
|
|
SymbolTable::build_on_ast(ast);
|
|
Interpreter::exec(ast);
|
|
} catch (const runtime_error& e) {
|
|
cerr << e.what() << endl;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
return -1;
|
|
}
|
|
|
|
// vim: et ts=4 sw=4 cin cino={1s ff=unix
|
|
|
|
|