floop.c

#include "mpc.h"

#ifdef _WIN32
static char buffer[2048];

char* readline(char* prompt) {
    fputs(prompt, stdout);
    fgets(buffer, 2048, stdin);
    char* cpy = malloc(strlen(buffer)+1);
    strcpy(cpy, buffer);
    cpy[strlen(cpy)-1] = '\0';
    return cpy;
}

void add_history(char* unused) {}

#else
#include <editline/readline.h>
#include <editline/history.h>
#endif


/* Forward declarations */

mpc_parser_t* Number;
mpc_parser_t* Symbol;
mpc_parser_t* String;
mpc_parser_t* Comment;
mpc_parser_t* Sexpr;
mpc_parser_t* Qexpr;
mpc_parser_t* Expr;
mpc_parser_t* Floop;

struct lval;
struct lenv;
typedef struct lval lval;
typedef struct lenv lenv;

/* Lisp value */

enum { LVAL_ERR, LVAL_NUM, LVAL_SYM, LVAL_STR,
LVAL_FUN, LVAL_SEXPR, LVAL_QEXPR };

typedef lval*(*lbuiltin)(lenv*, lval*);

struct lval {
    int type;

    long num;
    char* err;
    char* sym;
    char* str;

    lbuiltin builtin;
    lenv* env;
    lval* formals;
    lval* body;

    int count;
    lval** cell;
};

lval* lval_num(long x) {
    lval* v = malloc(sizeof(lval));
    v->type = LVAL_NUM;
    v->num = x;
    return v;
}

lval* lval_err(char* fmt, ...) {
    lval* v = malloc(sizeof(lval));
    v->type = LVAL_ERR;

    va_list va;
    va_start(va, fmt);

    v->err = malloc(512);
    vsnprintf(v->err, 511, fmt, va);
    v->err = realloc(v->err, strlen(v->err)+1);

    va_end(va);
    return v;
}

lval* lval_sym(char* s) {
    lval* v = malloc(sizeof(lval));
    v->type = LVAL_SYM;
    v->sym = malloc(strlen(s) + 1);
    strcpy(v->sym, s);
    return v;
}


lval* lval_str(char* s) {
    lval* v = malloc(sizeof(lval));
    v->type = LVAL_STR;
    v->str = malloc(strlen(s) + 1);
    strcpy(v->str, s);
    return v;
}

lval* lval_builtin(lbuiltin func) {
    lval* v = malloc(sizeof(lval));
    v->type = LVAL_FUN;
    v->builtin = func;
    return v;
}

lenv* lenv_new(void);

lval* lval_lambda(lval* formals, lval* body) {
    lval* v = malloc(sizeof(lval));
    v->type = LVAL_FUN;
    v->builtin = NULL;
    v->env = lenv_new();
    v->formals = formals;
    v->body = body;
    return v;
}

lval* lval_sexpr(void) {
    lval* v = malloc(sizeof(lval));
    v->type = LVAL_SEXPR;
    v->count = 0;
    v->cell = NULL;
    return v;
}

lval* lval_qexpr(void) {
    lval* v = malloc(sizeof(lval));
    v->type = LVAL_QEXPR;
    v->count = 0;
    v->cell = NULL;
    return v;
}

void lenv_del(lenv* e);

void lval_del(lval* v) {
    switch (v->type) {
        case LVAL_NUM: break;
        case LVAL_FUN:
            if (!v->builtin) {
                lenv_del(v->env);
                lval_del(v->formals);
                lval_del(v->body);
            }
            break;
        case LVAL_ERR: free(v->err); break;
        case LVAL_SYM: free(v->sym); break;
        case LVAL_STR: free(v->str); break;

        case LVAL_QEXPR:
        case LVAL_SEXPR:
            for (int i = 0; i < v->count; i++) {
                lval_del(v->cell[i]);
            }
            free(v->cell);
            break;
    }
    free(v);
}

lenv* lenv_copy(lenv* e);

lval* lval_copy(lval* v) {
    lval* x = malloc(sizeof(lval));
    x->type = v->type;

    switch (v->type) {
        case LVAL_FUN:
            if (v->builtin) {
                x->builtin = v->builtin;
            } else {
                x->builtin = NULL;
                x->env = lenv_copy(v->env);
                x->formals = lval_copy(v->formals);
                x->body = lval_copy(v->body);
            }
            break;
        case LVAL_NUM: x->num = v->num; break;

        case LVAL_ERR:
            x->err = malloc(strlen(v->err) + 1);
            strcpy(x->err, v->err); break;

        case LVAL_SYM:
            x->sym = malloc(strlen(v->sym) + 1);
            strcpy(x->sym, v->sym); break;

        case LVAL_STR: x->str = malloc(strlen(v->str) + 1);
            strcpy(x->str, v->str); break;

        case LVAL_SEXPR:
        case LVAL_QEXPR:
            x->count = v->count;
            x->cell = malloc(sizeof(lval*) * x->count);
            for (int i = 0; i < x->count; i++) {
                x->cell[i] = lval_copy(v->cell[i]);

            }
            break;
    }
    return x;
}

lval* lval_add(lval* v, lval* x) {
    v->count++;
    v->cell = realloc(v->cell, sizeof(lval*) * v->count);
    v->cell[v->count-1] = x;
    return v;
}

lval* lval_pop(lval* v, int i) {
    lval* x = v->cell[i];
    memmove(&v->cell[i], &v->cell[i+1],
            sizeof(lval*) * (v->count-i-1));

    v->count--;
    v->cell = realloc(v->cell, sizeof(lval*) * v->count);
    return x;
}

lval* lval_take(lval* v, int i) {
    lval* x = lval_pop(v, i);
    lval_del(v);
    return x;
}

lval* lval_join(lval* x, lval* y) {
    for (int i = 0; i < y->count; i++) {
        x = lval_add(x, y->cell[i]);
    }

    free(y->cell);
    free(y);
    return x;
}

void lval_print(lval* v);

void lval_print_str(lval* v) {
    char* escaped = malloc(strlen(v->str)+1);
    strcpy(escaped, v->str);

    escaped = mpcf_escape(escaped);
    printf("\"%s\"", escaped);
    free(escaped);
}

void lval_print_expr(lval* v, char open, char close) {
    putchar(open);
    for (int i = 0; i < v->count; i++) {
        lval_print(v->cell[i]);
        if (i != (v->count-1)) {
            putchar(' ');
        }
    }
    putchar(close);
}

void lval_print(lval* v) {
    switch (v->type) {
        case LVAL_FUN:
            if (v->builtin) {
                printf("<builtin>");
            } else {
                printf("(\\ "); lval_print(v->formals);
                putchar(' '); lval_print(v->body); putchar(')');
            }
            break;
        case LVAL_NUM: printf("%li", v->num); break;
        case LVAL_ERR: printf("Error: %s", v->err); break;
        case LVAL_SYM: printf("%s", v->sym); break;
        case LVAL_STR: lval_print_str(v); break;
        case LVAL_SEXPR: lval_print_expr(v, '(', ')'); break;
        case LVAL_QEXPR: lval_print_expr(v, '{', '}'); break;
    }
}

void lval_println(lval* v) { lval_print(v); putchar('\n'); }

char* ltype_name(int t) {
    switch(t) {
        case LVAL_FUN: return "Function";
        case LVAL_NUM: return "Number";
        case LVAL_ERR: return "Error";
        case LVAL_SYM: return "Symbol";
        case LVAL_STR: return "String";
        case LVAL_SEXPR: return "S-Expression";
        case LVAL_QEXPR: return "Q-Expression";
        default: return "Unknown";
    }
}

/* Lisp environment */

struct lenv {
    lenv* par;
    int count;
    char** syms;
    lval** vals;
};

lenv* lenv_new(void) {
    lenv* e = malloc(sizeof(lenv));
    e->par = NULL;
    e->count = 0;
    e->syms = NULL;
    e->vals = NULL;
    return e;
}

void lenv_del(lenv* e) {
    for (int i = 0; i < e->count; i++) {
        free(e->syms[i]);
        lval_del(e->vals[i]);
    }

    free(e->syms);
    free(e->vals);
    free(e);
}

lenv* lenv_copy(lenv* e) {
    lenv* n = malloc(sizeof(lenv));
    n->par = e->par;
    n->count = e->count;
    n->syms = malloc(sizeof(char*) * n->count);
    n->vals = malloc(sizeof(lval*) * n->count);

    for (int i = 0; i < e->count; i++) {
        n->syms[i] = malloc(strlen(e->syms[i]) + 1);
        strcpy(n->syms[i], e->syms[i]);
        n->vals[i] = lval_copy(e->vals[i]);
    }

    return n;
}

lval* lenv_get(lenv* e, lval* k) {
    for (int i = 0; i < e->count; i++) {
        if (strcmp(e->syms[i], k->sym) == 0) {
            return lval_copy(e->vals[i]);
        }
    }

    if (e->par) {
        return lenv_get(e->par, k);
    } else {
        return lval_err("Unbound symbol '%s'", k->sym);
    }
}

void lenv_put(lenv* e, lval* k, lval* v) {
    for (int i = 0; i < e->count; i++) {
        if (strcmp(e->syms[i], k->sym) == 0) {
            lval_del(e->vals[i]);
            e->vals[i] = lval_copy(v);
            return;
        }
    }

    e->count++;
    e->vals = realloc(e->vals, sizeof(lval*) * e->count);
    e->syms = realloc(e->syms, sizeof(char*) * e->count);

    e->vals[e->count-1] = lval_copy(v);
    e->syms[e->count-1] = malloc(strlen(k->sym)+1);
    strcpy(e->syms[e->count-1], k->sym);
}

void lenv_def(lenv* e, lval* k, lval* v) {
    while (e->par) { e = e->par; }
    lenv_put(e, k, v);
}

/* Builtins */

#define LASSERT(args, cond, fmt, ...)               \
    if (!(cond)) {                                  \
        lval* err = lval_err(fmt, ##__VA_ARGS__);   \
        lval_del(args);                             \
        return err;                                 \
    }

#define LASSERT_TYPE(func, args, index, expect)                         \
    LASSERT(args, args->cell[index]->type == expect,                    \
            "Function '%s' passed incorrect type for argument %i. Got %s, expected %s.", \
            func, index, ltype_name(args->cell[index]->type), ltype_name(expect))

#define LASSERT_NUM(func, args, num)                                    \
    LASSERT(args, args->count == num,                                   \
            "Function '%s' passed incorrect number of arguments. Got %i, expected %i.", \
            func, args->count, num)

#define LASSERT_NOT_EMPTY(func, args, index)                            \
    LASSERT(args, args->cell[index]->count != 0,                        \
            "Function '%s' passed {} for argument %i.", func, index);

lval* lval_eval(lenv* e, lval* v);

lval* builtin_lambda(lenv* e, lval* a) {
    LASSERT_NUM("\\", a, 2);
    LASSERT_TYPE("\\", a, 0, LVAL_QEXPR);
    LASSERT_TYPE("\\", a, 1, LVAL_QEXPR);

    for (int i = 0; i < a->cell[0]->count; i++) {
        LASSERT(a, (a->cell[0]->cell[i]->type == LVAL_SYM),
                "Cannot define non-symbol. Got %s, expected %s.",
                ltype_name(a->cell[0]->cell[i]->type),ltype_name(LVAL_SYM));

    }

    lval* formals = lval_pop(a, 0);
    lval* body = lval_pop(a, 0);
    lval_del(a);

    return lval_lambda(formals, body);
}

lval* builtin_list(lenv* e, lval* a) {
    a->type = LVAL_QEXPR;
    return a;
}

lval* builtin_head(lenv* e, lval* a) {
    LASSERT_NUM("head", a, 1);
    LASSERT_TYPE("head", a, 0, LVAL_QEXPR);
    LASSERT_NOT_EMPTY("head", a, 0);

    lval* v = lval_take(a, 0);
    while (v->count > 1) { lval_del(lval_pop(v, 1)); }
    return v;
}

lval* builtin_tail(lenv* e, lval* a) {
    LASSERT_NUM("tail", a, 1);
    LASSERT_TYPE("tail", a, 0, LVAL_QEXPR);
    LASSERT_NOT_EMPTY("tail", a, 0);

    lval* v = lval_take(a, 0);
    lval_del(lval_pop(v, 0));
    return v;
}

lval* builtin_eval(lenv* e, lval* a) {
    LASSERT_NUM("eval", a, 1);
    LASSERT_TYPE("eval", a, 0, LVAL_QEXPR);

    lval* x = lval_take(a, 0);
    x->type = LVAL_SEXPR;
    return lval_eval(e, x);
}

lval* builtin_join(lenv* e, lval* a) {
    for (int i = 0; i < a->count; i++) {
        LASSERT_TYPE("join", a, i, LVAL_QEXPR);
    }

    lval* x = lval_pop(a, 0);
    while (a->count) {
        lval* y = lval_pop(a, 0);
        x = lval_join(x, y);
    }

    lval_del(a);
    return x;
}

lval* builtin_op(lenv* e, lval* a, char* op) {
    for (int i = 0; i < a->count; i++) {
        LASSERT_TYPE(op, a, i, LVAL_NUM);
    }

    lval* x = lval_pop(a, 0);
    if ((strcmp(op, "-") == 0) && a->count == 0) {
        x->num = -x->num;
    }

    while (a->count > 0) {
        lval* y = lval_pop(a, 0);

        if (strcmp(op, "+") == 0) { x->num += y->num; }
        if (strcmp(op, "-") == 0) { x->num -= y->num; }
        if (strcmp(op, "*") == 0) { x->num *= y->num; }
        if (strcmp(op, "%") == 0) { x->num %= y->num; }
        if (strcmp(op, "^") == 0) { x->num = pow(x->num, y->num); }
        if (strcmp(op, "/") == 0) {
            if (y->num == 0) {
                lval_del(x); lval_del(y);
                x = lval_err("Division by zero!"); break;
            }
            x->num /= y->num;
        }
        lval_del(y);
    }
    lval_del(a);
    return x;
}

lval* builtin_add(lenv* e, lval* a) { return builtin_op(e, a, "+"); }
lval* builtin_sub(lenv* e, lval* a) { return builtin_op(e, a, "-"); }
lval* builtin_mul(lenv* e, lval* a) { return builtin_op(e, a, "*"); }
lval* builtin_div(lenv* e, lval* a) { return builtin_op(e, a, "/"); }
lval* builtin_mod(lenv* e, lval* a) { return builtin_op(e, a, "%"); }
lval* builtin_exp(lenv* e, lval* a) { return builtin_op(e, a, "^"); }

lval* builtin_ord(lenv* e, lval* a, char* op) {
    LASSERT_NUM(op, a, 2);
    LASSERT_TYPE(op, a, 0, LVAL_NUM);
    LASSERT_TYPE(op, a, 1, LVAL_NUM);

    int r;
    if (strcmp(op, ">") == 0) {
        r = (a->cell[0]->num > a->cell[1]->num);
    }
    if (strcmp(op, "<") == 0) {
        r = (a->cell[0]->num < a->cell[1]->num);
    }
    if (strcmp(op, ">=") == 0) {
        r = (a->cell[0]->num >= a->cell[1]->num);
    }
    if (strcmp(op, "<=") == 0) {
        r = (a->cell[0]->num <= a->cell[1]->num);
    }

    lval_del(a);
    return lval_num(r);
}

lval* builtin_gt(lenv* e, lval* a) { return builtin_ord(e, a, ">"); }
lval* builtin_lt(lenv* e, lval* a) { return builtin_ord(e, a, "<"); }
lval* builtin_ge(lenv* e, lval* a) { return builtin_ord(e, a, ">="); }
lval* builtin_le(lenv* e, lval* a) { return builtin_ord(e, a, "<="); }

int lval_eq(lval* x, lval* y) {
    if (x->type != y->type) { return 0; }
    switch (x->type) {
        case LVAL_NUM: return (x->num == y->num);
        case LVAL_ERR: return (strcmp(x->err, y->err) == 0);
        case LVAL_SYM: return (strcmp(x->sym, y->sym) == 0);
        case LVAL_STR: return (strcmp(x->str, y->str) == 0);

        case LVAL_FUN:
            if (x->builtin || y->builtin) {
                return x->builtin == y->builtin;
            } else {
                return lval_eq(x->formals, y->formals)
                    && lval_eq(x->body, y->body);
            }

        case LVAL_QEXPR:
        case LVAL_SEXPR:
            if (x->count != y->count) { return 0; }
            for (int i = 0; i < x->count; i++) {
                if (!lval_eq(x->cell[i], y->cell[i])) { return 0; }
            }

            return 1;
        break;
    }

    return 0;
}

lval* builtin_cmp(lenv* e, lval* a, char* op) {
    LASSERT_NUM(op, a, 2);
    int r;

    if (strcmp(op, "==") == 0) {
        r = lval_eq(a->cell[0], a->cell[1]);
    }
    if (strcmp(op, "!=") == 0) {
        r = !lval_eq(a->cell[0], a->cell[1]);
    }

    lval_del(a);
    return lval_num(r);
}

lval* builtin_eq(lenv* e, lval* a) { return builtin_cmp(e, a, "=="); }
lval* builtin_ne(lenv* e, lval* a) { return builtin_cmp(e, a, "!="); }

lval* builtin_if(lenv* e, lval* a) {
    LASSERT_NUM("if", a, 3);
    LASSERT_TYPE("if", a, 0, LVAL_NUM);
    LASSERT_TYPE("if", a, 1, LVAL_QEXPR);
    LASSERT_TYPE("if", a, 2, LVAL_QEXPR);

    lval* x;
    a->cell[1]->type = LVAL_SEXPR;
    a->cell[2]->type = LVAL_SEXPR;

    if (a->cell[0]->num) {
        x = lval_eval(e, lval_pop(a, 1));
    } else {
        x = lval_eval(e, lval_pop(a, 2));
    }

    lval_del(a);
    return x;
}

lval* builtin_var(lenv* e, lval* a, char* func) {
    LASSERT_TYPE(func, a, 0, LVAL_QEXPR);

    lval* syms = a->cell[0];
    for (int i = 0; i < syms->count; i++) {
        LASSERT(a, (syms->cell[i]->type == LVAL_SYM),
                "Function '%s' cannot define non-symbol. "
                "Got %s, expected %s.", func,
                ltype_name(syms->cell[i]->type),
                ltype_name(LVAL_SYM));
    }

    LASSERT(a, (syms->count == a->count-1),
            "Function '%s' passed too many arguments for symbols. "
            "Got %i, expected %i.", func,
            syms->count, a->count-1);

    for (int i = 0; i < syms->count; i++) {
        if (strcmp(func, "def") == 0) {
            lenv_def(e, syms->cell[i], a->cell[i+1]);
        }

        if (strcmp(func, "=") == 0) {
            lenv_put(e, syms->cell[i], a->cell[i+1]);
        }
    }

    lval_del(a);
    return lval_sexpr();
}

lval* builtin_def(lenv* e, lval* a) {
    return builtin_var(e, a, "def");
}

lval* builtin_put(lenv* e, lval* a) {
    return builtin_var(e, a, "=");
}

lval* lval_read(mpc_ast_t* t);

lval* builtin_load(lenv* e, lval* a) {
    LASSERT_NUM("load", a, 1);
    LASSERT_TYPE("load", a, 0, LVAL_STR);

    mpc_result_t r;
    if (mpc_parse_contents(a->cell[0]->str, Floop, &r)) {
        lval* expr = lval_read(r.output);
        mpc_ast_delete(r.output);

        while (expr->count) {
            lval* x = lval_eval(e, lval_pop(expr, 0));
            if (x->type == LVAL_ERR) { lval_println(x); }
            lval_del(x);
        }

        lval_del(expr);
        lval_del(a);

        return lval_sexpr();
    } else {
        char* err_msg = mpc_err_string(r.error);
        mpc_err_delete(r.error);

        lval* err = lval_err("Could not load file %s", err_msg);
        free(err_msg);
        lval_del(a);

        return err;
    }
}

lval* builtin_print(lenv* e, lval* a) {
    for (int i = 0; i < a->count; i++) {
        lval_print(a->cell[i]); putchar(' ');
    }

    putchar('\n');
    lval_del(a);

    return lval_sexpr();
}

lval* builtin_error(lenv* e, lval* a) {
    LASSERT_NUM("error", a, 1);
    LASSERT_TYPE("error", a, 0, LVAL_STR);

    lval* err = lval_err(a->cell[0]->str);

    lval_del(a);
    return err;
}

void lenv_add_builtin(lenv* e, char* name, lbuiltin func) {
    lval* k = lval_sym(name);
    lval* v = lval_builtin(func);
    lenv_put(e, k, v);
    lval_del(k); lval_del(v);
}

void lenv_add_builtins(lenv* e) {
    lenv_add_builtin(e, "\\", builtin_lambda);
    lenv_add_builtin(e, "def", builtin_def);
    lenv_add_builtin(e, "=", builtin_put);

    lenv_add_builtin(e, "list", builtin_list);
    lenv_add_builtin(e, "head", builtin_head);
    lenv_add_builtin(e, "tail", builtin_tail);
    lenv_add_builtin(e, "eval", builtin_eval);
    lenv_add_builtin(e, "join", builtin_join);

    lenv_add_builtin(e, "+", builtin_add);
    lenv_add_builtin(e, "-", builtin_sub);
    lenv_add_builtin(e, "*", builtin_mul);
    lenv_add_builtin(e, "/", builtin_div);
    lenv_add_builtin(e, "%", builtin_mod);
    lenv_add_builtin(e, "^", builtin_exp);

    lenv_add_builtin(e, "if", builtin_if);
    lenv_add_builtin(e, "==", builtin_eq);
    lenv_add_builtin(e, "!=", builtin_ne);
    lenv_add_builtin(e, ">", builtin_gt);
    lenv_add_builtin(e, "<", builtin_lt);
    lenv_add_builtin(e, ">=", builtin_ge);
    lenv_add_builtin(e, "<=", builtin_le);

    lenv_add_builtin(e, "load", builtin_load);
    lenv_add_builtin(e, "error", builtin_error);
    lenv_add_builtin(e, "print", builtin_print);
}

lval* lval_call(lenv* e, lval* f, lval* a) {
    if (f->builtin) { return f->builtin(e, a); }

    int given = a->count;
    int total = f->formals->count;

    while (a->count) {
        if (f->formals->count == 0) {
            lval_del(a);
            return lval_err("Function passed too many arguments. "
                            "Got %i, expected %i.", given, total);
        }

        lval* sym = lval_pop(f->formals, 0);

        if (strcmp(sym->sym, "&") == 0) {
            if (f->formals->count != 1) {
                lval_del(a);
                return lval_err("Function format invalid. "
                                "Symbol '&' not followed by single symbol.");
            }

            lval* nsym = lval_pop(f->formals, 0);
            lenv_put(f->env, nsym, builtin_list(e, a));
            lval_del(sym); lval_del(nsym);
            break;
        }

        lval* val = lval_pop(a, 0);
        lenv_put(f->env, sym, val);

        lval_del(sym); lval_del(val);
    }

    lval_del(a);
    if (f->formals->count > 0 &&
        strcmp(f->formals->cell[0]->sym, "&") == 0) {
        if (f->formals->count != 2) {
            return lval_err("Function format invalid. "
                            "Symbol '&' not followed by single symbol.");
        }

        lval_del(lval_pop(f->formals, 0));

        lval* sym = lval_pop(f->formals, 0);
        lval* val = lval_qexpr();

        lenv_put(f->env, sym, val);
        lval_del(sym); lval_del(val);
    }

    if (f->formals->count == 0) {
        f->env->par = e;
        return builtin_eval(f->env,
                            lval_add(lval_sexpr(), lval_copy(f->body)));
    } else {
        return lval_copy(f);
    }
}

lval* lval_eval_sexpr(lenv* e, lval* v) {
    for (int i = 0; i < v->count; i++) {
        v->cell[i] = lval_eval(e, v->cell[i]);
    }

    for (int i = 0; i < v->count; i++) {
        if (v->cell[i]->type == LVAL_ERR) { return lval_take(v, i); }
    }

    if (v->count == 0) { return v; }
    if (v->count == 1) { return lval_eval(e, lval_take(v, 0)); }

    lval* f = lval_pop(v, 0);
    if (f->type != LVAL_FUN) {
        lval* err = lval_err(
            "S-Expression starts with incorrect type. "
            "Got %s, expected %s.",
            ltype_name(f->type), ltype_name(LVAL_FUN));

        lval_del(f); lval_del(v);
        return err;
    }

    lval* result = lval_call(e, f, v);
    lval_del(f);
    return result;
}

lval* lval_eval(lenv* e, lval* v) {
    if (v->type == LVAL_SYM) {
        lval* x = lenv_get(e, v);
        lval_del(v);
        return x;
    }

    if (v->type == LVAL_SEXPR) { return lval_eval_sexpr(e, v); }
    return v;
}

lval* lval_read_num(mpc_ast_t* t) {
    errno = 0;
    long x = strtol(t->contents, NULL, 10);
    return errno != ERANGE ?
        lval_num(x) : lval_err("invalid number");
}

lval* lval_read_str(mpc_ast_t* t) {
    t->contents[strlen(t->contents)-1] = '\0';
    char* unescaped = malloc(strlen(t->contents+1)+1);
    strcpy(unescaped, t->contents+1);

    unescaped = mpcf_unescape(unescaped);
    lval* str = lval_str(unescaped);
    free(unescaped);
    return str;
}

lval* lval_read(mpc_ast_t* t) {
    if (strstr(t->tag, "number")) { return lval_read_num(t); }
    if (strstr(t->tag, "symbol")) { return lval_sym(t->contents); }
    if (strstr(t->tag, "string")) { return lval_read_str(t); }

    lval* x = NULL;
    if (strcmp(t->tag, ">") == 0) { x = lval_sexpr(); }
    if (strstr(t->tag, "sexpr")) { x = lval_sexpr(); }
    if (strstr(t->tag, "qexpr")) { x = lval_qexpr(); }

    for (int i = 0; i < t->children_num; i++) {
        if (strcmp(t->children[i]->contents, "(") == 0) { continue; }
        if (strcmp(t->children[i]->contents, ")") == 0) { continue; }
        if (strcmp(t->children[i]->contents, "}") == 0) { continue; }
        if (strcmp(t->children[i]->contents, "{") == 0) { continue; }
        if (strstr(t->children[i]->tag, "comment")) { continue; }
        if (strcmp(t->children[i]->tag, "regex") == 0) { continue ; }
        x = lval_add(x, lval_read(t->children[i]));
    }

    return x;
}


/* Main */

int main(int argc, char** argv) {
    Number  = mpc_new("number");
    Symbol  = mpc_new("symbol");
    String  = mpc_new("string");
    Comment = mpc_new("comment");
    Sexpr   = mpc_new("sexpr");
    Qexpr   = mpc_new("qexpr");
    Expr    = mpc_new("expr");
    Floop   = mpc_new("floop");

    mpca_lang(MPCA_LANG_DEFAULT,
    "                                                       \
    number  : /-?[0-9]+/ ;                                  \
    symbol  : /[a-zA-Z0-9_+\\-%\\^*\\/\\\\=<>!&]+/ ;        \
    string  : /\"(\\\\.|[^\"])*\"/ ;                        \
    comment : /;[^\\r\\n]*/ ;                               \
    sexpr   : '(' <expr>* ')' ;                             \
    qexpr   : '{' <expr>* '}' ;                             \
    expr    : <number>  | <symbol> | <string>               \
            | <comment> | <sexpr>  | <qexpr> ;              \
    floop   : /^/ <expr>* /$/ ;                             \
    ", Number, Symbol, String, Comment, Sexpr, Qexpr, Expr, Floop);

    lenv* e = lenv_new();
    lenv_add_builtins(e);

    if (argc == 1) {
        puts("\n");
        puts("     ▄████████  ▄█        ▄██████▄   ▄██████▄     ▄███████▄ ");
        puts("   ███    ███ ███       ███    ███ ███    ███   ███    ███  ");
        puts("   ███    █▀  ███       ███    ███ ███    ███   ███    ███  ");
        puts("  ▄███▄▄▄     ███       ███    ███ ███    ███   ███    ███  ");
        puts(" ▀▀███▀▀▀     ███       ███    ███ ███    ███ ▀█████████▀   ");
        puts("   ███        ███       ███    ███ ███    ███   ███         ");
        puts("   ███        ███▌    ▄ ███    ███ ███    ███   ███         ");
        puts("   ███        █████▄▄██  ▀██████▀   ▀██████▀   ▄████▀       ");
        puts("              ▀                                           \n");

        puts("Press Ctrl+c to exit\n");

        while (1) {
            char* input = readline("floop> ");
            add_history(input);

            mpc_result_t r;
            if (mpc_parse("<stdin>", input, Floop, &r)) {
                lval* x = lval_eval(e, lval_read(r.output));
                lval_println(x);
                lval_del(x);

                mpc_ast_delete(r.output);
            } else {
                mpc_err_print(r.error);
                mpc_err_delete(r.error);
            }

            free(input);
        }
    }

    if (argc >= 2) {
        for (int i = 1; i < argc; i++) {
            lval* args = lval_add(lval_sexpr(), lval_str(argv[i]));
            lval* x = builtin_load(e, args);

            if (x->type == LVAL_ERR) { lval_println(x); }
            lval_del(x);
        }
    }

    lenv_del(e);

    mpc_cleanup(8,
                Number, Symbol, String, Comment,
                Sexpr, Qexpr, Expr, Floop);
    return 0;
}