c-repl/src/interpreter.cpp

#include <vector>
#include <string>
#include <iostream>
#include "include/parser.h"
#include "include/interpreter.h"
#include "include/memory.h"
using namespace std;

bool bool_cast(EvalResult value) {
    if (holds_alternative<int>(value)) {
        return get<int>(value) != 0;
    }
    else if (holds_alternative<double>(value)) {
        return get<double>(value) != 0;
    }
    else {
        throw;
    }
}

int int_cast(EvalResult value) {
    if (holds_alternative<int>(value)) {
        return get<int>(value);
    } else if (holds_alternative<double>(value)) {
        return int(get<double>(value));
    }
    else {
        throw;
    }
}

double double_cast(EvalResult value) {
    if (holds_alternative<int>(value)) {
        return double(get<int>(value));
    }
    else if (holds_alternative<double>(value)) {
        return get<double>(value);
    }
    else {
        throw;
    }
}

EvalResult eval(Node &ast, Memory &memory) {
    if (holds_alternative<InnerNode>(ast)) {
        InnerNode node = get<InnerNode>(ast);
        switch (node.type) {
            case NodeType::Prog:
                eval(node.children[0], memory);
                return eval(node.children[1], memory);
            break;
            case NodeType::Epsilon:
                return {};
            break;
            case NodeType::If: {
                int cond = bool_cast(eval(node.children[0], memory));
                
                if (cond) {
                    eval(node.children[1], memory);
                }

                return {};
            } break;
            case NodeType::IfElse: {
                int cond = bool_cast(eval(node.children[0], memory));
                
                if (cond) {
                    eval(node.children[1], memory);
                }
                else {
                    eval(node.children[2], memory);
                }

                return {};
            } break;
            case NodeType::While: {
                while (true) {
                    int cond = bool_cast(eval(node.children[0], memory));
                    if (!cond) break;

                    eval(node.children[1], memory);
                }

                return {};
            } break;
            case NodeType::For: {
                memory.add_scope(ScopeType::For);

                eval(node.children[0], memory);

                while (true) {
                    int cond = bool_cast(eval(node.children[1], memory));
                    if (!cond) break;

                    eval(node.children[3], memory);
                    eval(node.children[2], memory);
                }

                memory.remove_scope();

                return {};
            } break;
            case NodeType::Bloc: {
                memory.add_scope(ScopeType::Block);
                eval(node.children[0], memory);
                memory.remove_scope();
                return {};
            } break;
            case NodeType::Eq: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);
                
                return e1 == e2;
            } break;
            case NodeType::Neq: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);
                
                return e1 != e2;
            } break;
            case NodeType::Lor: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);
                
                return bool_cast(e1) || bool_cast(e2);
            } break;
            case NodeType::Land: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);
                
                return bool_cast(e1) && bool_cast(e2);
            } break;
            case NodeType::Neg: {
                EvalResult e1 = eval(node.children[0], memory);

                return !bool_cast(e1);
            } break;
            case NodeType::Lt: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);
                
                return e1 < e2;
            } break;
            case NodeType::Gt: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);
                
                return e1 > e2;
            } break;
            case NodeType::Leq: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);
                
                return e1 <= e2;
            } break;
            case NodeType::Geq: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);
                
                return e1 >= e2;
            } break;
            case NodeType::Plus: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);

                if (holds_alternative<double>(e1) || holds_alternative<double>(e2)) {
                    double d1 = double_cast(e1);
                    double d2 = double_cast(e2);
                    return d1 + d2;
                }
                else {
                    int i1 = get<int>(e1);
                    int i2 = get<int>(e2);
                    return i1 + i2;
                }
            } break;
            case NodeType::Minus: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);

                if (holds_alternative<double>(e1) || holds_alternative<double>(e2)) {
                    double d1 = double_cast(e1);
                    double d2 = double_cast(e2);
                    return d1 - d2;
                }
                else {
                    int i1 = get<int>(e1);
                    int i2 = get<int>(e2);
                    return i1 - i2;
                }
            } break;
            case NodeType::Mult: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);

                if (holds_alternative<double>(e1) || holds_alternative<double>(e2)) {
                    double d1 = double_cast(e1);
                    double d2 = double_cast(e2);
                    return d1 * d2;
                }
                else {
                    int i1 = get<int>(e1);
                    int i2 = get<int>(e2);
                    return i1 * i2;
                }
            } break;
            case NodeType::Div: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);

                if (holds_alternative<double>(e1) || holds_alternative<double>(e2)) {
                    double d1 = double_cast(e1);
                    double d2 = double_cast(e2);
                    if (d2 == 0) throw RuntimeError("Division by 0", node.pos);
                    return d1 / d2;
                }
                else {
                    int i1 = get<int>(e1);
                    int i2 = get<int>(e2);
                    if (i2 == 0) throw RuntimeError("Division by 0", node.pos);
                    return i1 / i2;
                }
            } break;
            case NodeType::Mod: {
                EvalResult e1 = eval(node.children[0], memory);
                EvalResult e2 = eval(node.children[1], memory);

                int i1 = get<int>(e1);
                int i2 = get<int>(e2);
                if (i2 == 0) throw RuntimeError("Modulo by 0", node.pos);
                return i1 % i2;
            } break;
            case NodeType::UnaryPlus: {
                EvalResult e1 = eval(node.children[0], memory);
                
                if (holds_alternative<int>(e1)) {
                    return +get<int>(e1);
                }
                else if (holds_alternative<double>(e1)) {
                    return +get<double>(e1);
                }
            } break;
            case NodeType::UnaryMinus: {
                EvalResult e1 = eval(node.children[0], memory);
                
                if (holds_alternative<int>(e1)) {
                    return -get<int>(e1);
                }
                else if (holds_alternative<double>(e1)) {
                    return -get<double>(e1);
                }
            } break;
            case NodeType::Declaration: {
                Token typeTok = get<Token>(node.children[0]);
                Token identifierTok = get<Token>(node.children[1]);
                Type type = get<Type>(typeTok.data);
                string identifier = get<string>(identifierTok.data);

                memory.declare(identifier, type);
                
                return {};
            } break;
            case NodeType::AssignedDeclaration: {
                Token typeTok = get<Token>(node.children[0]);
                Token identifierTok = get<Token>(node.children[1]);
                Type type = get<Type>(typeTok.data);
                string identifier = get<string>(identifierTok.data);
                EvalResult value = eval(node.children[2], memory);

                memory.declare(identifier, type);
                if (type == Type::Int) {
                    memory.update(identifier, int_cast(value));
                }
                else if (type == Type::Double) {
                    memory.update(identifier, double_cast(value));
                }

                return value;
            } break;
            case NodeType::Assignment: {
                Token identifierTok = get<Token>(node.children[0]);
                string identifier = get<string>(identifierTok.data);
                EvalResult value = eval(node.children[1], memory);

                Type type = memory.get(identifier).type;

                if (type == Type::Int) {
                    memory.update(identifier, int_cast(value));
                }
                else if (type == Type::Double) {
                    memory.update(identifier, double_cast(value));
                }

                return value;
            } break;
            case NodeType::LIncr: {
                Token identifierTok = get<Token>(node.children[0]);
                string identifier = get<string>(identifierTok.data);

                MemoryVar& var = memory.get(identifier);

                if (!var.initialized) {
                    throw RuntimeError("Accessing uninitialized identifier \""+identifier+"\"", identifierTok.pos);
                }
                else if (var.type == Type::Int) {
                    memory.update(identifier, get<int>(var.value) + 1);
                    return var.value;
                }
                else {
                    return var.value;
                }
            }
            case NodeType::RIncr: {
                Token identifierTok = get<Token>(node.children[0]);
                string identifier = get<string>(identifierTok.data);

                MemoryVar& var = memory.get(identifier);

                if (!var.initialized) {
                    throw RuntimeError("Accessing uninitialized identifier \""+identifier+"\"", identifierTok.pos);
                }
                else if (var.type == Type::Int) {
                    int oldVal = get<int>(var.value);
                    memory.update(identifier, oldVal + 1);
                    return oldVal;
                }
                else {
                    return var.value;
                }
            }
            case NodeType::LDecr: {
                Token identifierTok = get<Token>(node.children[0]);
                string identifier = get<string>(identifierTok.data);

                MemoryVar& var = memory.get(identifier);

                if (!var.initialized) {
                    throw RuntimeError("Accessing uninitialized identifier \""+identifier+"\"", identifierTok.pos);
                }
                else if (var.type == Type::Int) {
                    memory.update(identifier, get<int>(var.value) - 1);
                    return var.value;
                }
                else {
                    return var.value;
                }
            }
            case NodeType::RDecr: {
                Token identifierTok = get<Token>(node.children[0]);
                string identifier = get<string>(identifierTok.data);

                MemoryVar& var = memory.get(identifier);

                if (!var.initialized) {
                    throw RuntimeError("Accessing uninitialized identifier \""+identifier+"\"", identifierTok.pos);
                }
                else if (var.type == Type::Int) {
                    int oldVal = get<int>(var.value);
                    memory.update(identifier, oldVal - 1);
                    return oldVal;
                }
                else {
                    return var.value;
                }
            }
            default: {
                throw RuntimeError("Not Implemented", node.pos);
            }
        }
    }
    else {
        Token token = get<Token>(ast);
        switch (token.type) {
            case TokenType::Litteral: {
                if (holds_alternative<int>(token.data)) {
                    return get<int>(token.data);
                } else if (holds_alternative<double>(token.data)) {
                    return get<double>(token.data);
                }
                else {
                    throw;
                }
            } break;
            case TokenType::Identifier: {
                string identifier = get<string>(token.data);
                
                MemoryVar& var = memory.get(identifier);

                if (!var.initialized) throw RuntimeError("Accessing uninitialized identifier \""+identifier+"\"", token.pos);
                
                return var.value;
            } break;
            default:
                throw;
            break;
        }
    }

    return {};
}