BF.cpp

#include <iostream> // IO
#include <string> // String variable
#include <fstream> // File IO

#define HEAPSIZE 30000

// Prototypes
void lexer(std::string);
void parser(char);
void help();
void argHandler(int, char*[]);

// Prototypes for all the different BF commands
void ptrIncr();
void ptrDcrm();
void brkOpen();
void brkClose();
void valIncr();
void valDcrm();
void print();
void input();

// global variables
char array[HEAPSIZE] = {0};
char* arrPtr = array;
const char* commandPtr;

int main(int argc, char* argv[]) {
    argHandler(argc, argv);
}

void lexer(std::string program) {
    commandPtr = program.c_str(); // Is there any other way to do this?

    // This makes sure we keep going as long as there is a command to interpret
    // It seems a little hacky, is there any other way to do this?
    while(*commandPtr) {
        parser(*commandPtr);
        commandPtr++;
    }
}

void parser(char command) {
    switch(command) {
        case '>':
            ptrIncr();
            break;
        case '<':
            ptrDcrm();
            break;
        case '+':
            valIncr();
            break;
        case '-':
            valDcrm();
            break;
        case '[':
            brkOpen();
            break;
        case ']':
            brkClose();
            break;
        case '.':
            print();
            break;
        case ',':
            input();
            break;
    }
}

void argHandler(int argc, char* argv[]) {
    std::string program;
    if (argc == 1) {
        help();
        while(program != "exit") {
            std::cout << "BF> ";
            std::cin >> program;
            if(program == "help") {
                help();
            }
            lexer(program);
            std::cout << "\n";
        }
    } else {
        std::ifstream file(argv[1]); // Read in the file
        if(!file.is_open())
            std::cout << "ERROR: Opening file has failed";
        std::string program((std::istreambuf_iterator<char>(file)),
                std::istreambuf_iterator<char>()); // Found from SO, please explain
        lexer(program);
        std::cout << "\n";
    }
}

void help() {
    std::cout << "To exit, please type \"exit\", or hit ctrl-c. To see this again, please type \"help\"." << std::endl;
}

void ptrIncr() { // There should be some way for this to overflow
    arrPtr++;
}

void ptrDcrm() { // There should be some way for this to underflow
    arrPtr--;
}

void valIncr() {
    (*arrPtr) = ((*arrPtr) + 1) % 255;
}

void valDcrm() {
    (*arrPtr) = ((*arrPtr) - 1) % 255;
}

void brkOpen() {

    if((int)*arrPtr == 0) {
        int depth = 1;
        while(depth != 0) {
            commandPtr++;
            if(*commandPtr == '[')
                depth++;
            else if(*commandPtr == ']')
                depth--;
        }
    }

}

void brkClose() {

    if(!( (int)*arrPtr == 0 )) {
        int depth = 1;
        while(depth != 0) {
            commandPtr--;
            if(*commandPtr == '[')
                depth--;
            else if(*commandPtr == ']')
                depth++;
        }
    }

}

void print() {
    if((int)*arrPtr <= 31) {
        std::cout << "";
    } else {
        std::cout << *arrPtr;
    }
}

void input() {
    std::cin >> *arrPtr;
}

helloWorld.b

++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.

makefile

bf:
	g++ -Wall -o bf.exe bf.cpp
clean:
	rm -f *.exe