Brain Fuck Compiler In Rust to C

main.rs

#[derive(PartialEq,Debug,Clone, Copy)]
enum Token{
    Add, // +
    Sub, // _
    Right, // > 
    Left, // <
    Read, // , 
    Write, // . 
    BeginLoop, // [ 
    EndLoop, // ] 
}

use self::Token::*;

fn tokenize(input : &str)->Vec<Token>{
    let mut tokens = Vec::<Token>::new();
    let mut chars = input.chars();

    while let Some(c) = chars.next() {
        match c {
            '+' => tokens.push(Add),
            '-' => tokens.push(Sub),
            '>' => tokens.push(Right),
            '<' => tokens.push(Left),
            ',' => tokens.push(Read),
            '.' => tokens.push(Write),
            '[' => tokens.push(BeginLoop),
            ']' => tokens.push(EndLoop),
            _ => {}
        }
    }

    tokens
}

/// take tokens and generate a c source file 
fn generate(tokens : &[Token]) -> String{
    
    let mut output = String::new();let mut output = String::from(include_str!("preface.c"));
    
    for &token in tokens{
        match token{
            Add => {
                // Increment the value at the selected cell
                output.push_str("++*ptr;\n");
            },
            Sub => {
                // Decrement the value at the selected cell
                output.push_str("--*ptr;\n");
            },
            Right => {
                // Change our selected cell to the next to the right
                output.push_str("++ptr;\n");
            },
            Left => {
                // Change our selected cell to the next to the left
                output.push_str("--ptr;\n");
            },
            Read => {
                 // Read a single character into the selected cell
                 output.push_str("*ptr=getchar();\n");
            },
            Write => {
                // Print the character at the selected cell
                output.push_str("putchar(*ptr);\n");
            },
            BeginLoop => {
                // Begin a loop at the current cell
                output.push_str("while (*ptr) {\n");
            },
            EndLoop => {
                // Close a loop
                output.push_str("}\n");
            },
        };
    }
    output
}

static PROGRAM: &'static str = "++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.";

fn main() {
    let p = "+-><,.[] > + - ABC , .. DE . F";

    let tokens = tokenize(PROGRAM);
    println!("{:?}", tokens);

    let generated_code = generate(&tokens);
    println!("Generated code:\n{}", generated_code);

}

preface.c

#include stdio.h
int main()
{
    char tape[20000] = {0};
    char *ptr = tape;