commit

README.md

-# cproject
-
+# Lixp - A lisp implementation by C
+
+## Description
+
+This is a lisp implementation guided by [buildyourownlisp](http://www.buildyourownlisp.com/contents). 
+
+Video on [Youtube](https://youtu.be/tpd2qf2y1Ko).
+
+## Compile
+
+Just use `make`, but `libeditline` is required. 
+```
+$ make
+```
+
+## Launch 
+
+```
+$ ./lixp
+```
+
+## Usage
+
+Type in the interactive console. You can careate and interact the variables, use some built-in functions and define your own functions.
+
+### arthmetic operation
+```
+lixp> + 1 (* 2 8)
+17 
+```
+### define a function
+```
+(def {hello} "Hello World")
+```
+### some built-in function
+`list`,`head`, `join`, `tail`
+```
+lixp> list 1 2 3 4
+{1 2 3 4}
+lixp> head {1 2 4}
+{1}
+lixp> join {1 2} {3 4}
+{1 2 3 4}
+lixp> tail {1 2 3 4}
+{2 3 4}
+```
+### if statement
+```
+lixp> def {x y} 100 200
+ok    
+lixp> if (== x y) {+ x y} {- x y}
+-100  
+```
+### comment 
+```
+; this is a commment.
+```
+
+## Description of the files
+
+### util.c/h
+Defined some utilities
+### shared.c/h
+Global shared variables for setting up the parser.
+### mpc.c/h
+3rd-party lib for tokenizing input, defining a parser.
+### lval.c/h
+Data structres and functions for `lval`, which represents the minimal unit in the process of the computation of lixp.
+### lang.c/h
+implementation of the tokenizer and the parser of the lixp.
+### functions.c/h
+implementation of the built-in functions.
+
+## TODO
+
+* enable user to define a function
+* garbage collector
+* native type, not using `long ` in C
+* user defined type
+* OS interaction, i.e. file system
\ No newline at end of file

functions.h

+#ifndef FUNCTIONS_H
+#define	FUNCTIONS_H
+
+#include "lang.h"
+
+// define and implement built-in fuctions
+    
+typedef enum BUILTIN_OP_TYPE BUILTIN_OP_TYPE;
+    
+ enum BUILTIN_OP_TYPE {
+    BUILTIN_OP_ADD, BUILTIN_OP_SUB, BUILTIN_OP_DIV, BUILTIN_OP_MUL, BUILTIN_OP_POW,
+    BUILTIN_COMP_GT, BUILTIN_COMP_LT, BUILTIN_COMP_GE, BUILTIN_COMP_LE,
+    BUILTIN_COMP_EQ, BUILTIN_COMP_NEQ,
+    BUILTIN_LOGICAL_OR, BUILTIN_LOGICAL_AND, BUILTIN_LOGICAL_NOT
+};
+    
+char* builtin_op_strname(BUILTIN_OP_TYPE op);
+    
+void lenv_add_builtin(lenv* env, char* sym, lbuiltin func);
+    
+void lenv_add_builtin_funcs(lenv* env);
+    
+//Math functions
+lval* builtin_op(lenv* env, lval* val, BUILTIN_OP_TYPE op);
+lval* builtin_add(lenv* env, lval* val);
+lval* builtin_sub(lenv* env, lval* val);
+lval* builtin_div(lenv* env, lval* val);
+lval* builtin_mul(lenv* env, lval* val);
+lval* builtin_pow(lenv* env, lval* val);
+    
+//Comparison Functions
+lval* builtin_comp_num(lenv* env, lval* val, BUILTIN_OP_TYPE op);
+lval* builtin_comp_gt(lenv* env, lval* val);
+lval* builtin_comp_lt(lenv* env, lval* val);
+lval* builtin_comp_ge(lenv* env, lval* val);
+lval* builtin_comp_le(lenv* env, lval* val);
+lval* builtin_comp_value(lenv* env, lval* val, BUILTIN_OP_TYPE op);
+lval* builtin_comp_eq(lenv* env, lval* val);
+lval* builtin_comp_neq(lenv* env, lval* val);
+lval* builtin_logical(lenv* env, lval* val, BUILTIN_OP_TYPE op);
+lval* builtin_logical_and(lenv* env, lval* val);
+lval* builtin_logical_or(lenv* env, lval* val);
+lval* builtin_logical_not(lenv* env, lval* val);
+    
+//List/Util functions
+lval* builtin_list(lenv* env, lval* val);
+lval* builtin_eval(lenv* env, lval* val);
+lval* builtin_join(lenv* env, lval* val);
+lval* builtin_head(lenv* env, lval* val);
+lval* builtin_tail(lenv* env, lval* val);
+lval* builtin_if(lenv* env, lval* val);
+lval* builtin_print(lenv* env, lval* val);
+    
+//ENV Functions
+lval* builtin_envdef(lenv* env, lval* val, char* type);
+lval* builtin_def(lenv* env, lval* val);
+lval* builtin_var(lenv* env, lval* val);
+lval* builtin_listenv(lenv* env, lval* val);
+lval* builtin_exit(lenv* env, lval* val);
+lval* builtin_lambda(lenv* env, lval* val);
+lval* builtin_load(lenv* env, lval* val);
+lval* builtin_loadonce(lenv* env, lval* val);
+lval* builtin_do_load(lenv* env, lval* val, BOOL loadonce);
+lval* builtin_error(lenv* env, lval* val);
+    
+#endif	/* FUNCTIONS_H */
+

lang.c

+#include <float.h>
+#include <stdio.h>
+
+#include "mpc.h"
+#include "lang.h"
+
+mpc_ast_t* tokenize(char *input) {
+    mpc_result_t result;
+    int success = 1;
+    
+    if (!mpc_parse("<stdin>", input,gLispy, &result)) {
+        success = 0;
+        mpc_err_print_to(result.error, stderr);
+        mpc_err_delete(result.error);
+    }
+    
+    return success ? (mpc_ast_t*)result.output : NULL;
+}
+void setup_parsers() {
+    mpc_parser_t* Number = mpc_new("number");
+    mpc_parser_t* Ok = mpc_new("ok");
+    mpc_parser_t* Symbol = mpc_new("symbol");
+    mpc_parser_t* String = mpc_new("string");
+    mpc_parser_t* Comment = mpc_new("comment");
+    mpc_parser_t* S_Expr = mpc_new("s_expr");
+    mpc_parser_t* Q_Expr = mpc_new("q_expr");
+    mpc_parser_t* Expr = mpc_new("expr");
+    mpc_parser_t* Lispy = mpc_new("lispy");
+    
+    mpca_lang(MPCA_LANG_DEFAULT,
+        "                                                        \
+          number   : /-?[0-9]+(\\.[0-9]+)?/ ;                    \
+          ok       : /ok/ ;                                      \
+          symbol   : /[a-zA-Z0-9_+\\-*\\/\\\\=<>!&\\|]+/ ;       \
+          string   : /\"(\\\\.|[^\"])*\"/ ;                      \
+          comment  : /;[^\\r?\\n]*/ ;                            \
+          s_expr   : '(' <expr>* ')' ;                           \
+          q_expr   : '{' <expr>* '}' ;                           \
+          expr     : <number> | <ok> | <symbol> | <string>       \
+                   | <comment> | <s_expr> | <q_expr> ;           \
+          lispy    : /^/ <expr>+ /$/ ;                           \
+        ",
+        Number, Ok, Symbol, String, Comment, Expr, S_Expr, Q_Expr, Lispy);
+    
+    gLispy = Lispy;
+    gParsers = calloc(20, sizeof(mpc_parser_t*));
+    int i = 0;
+    gParsers[i++] = Number;
+    gParsers[i++] = Ok;
+    gParsers[i++] = Symbol;
+    gParsers[i++] = String;
+    gParsers[i++] = Comment;
+    gParsers[i++] = Q_Expr;
+    gParsers[i++] = S_Expr;
+    gParsers[i++] = Expr;
+    gParsers[i++] = Lispy;
+    gParsers = realloc(gParsers, sizeof(mpc_parser_t*)*i);
+    gParserCount = i;
+}
+void cleanup_parsers() {
+    for (int i = 0; i < gParserCount; i++) { mpc_undefine(gParsers[i]); }
+    for (int i = 0; i < gParserCount; i++) { mpc_delete(gParsers[i]); } 
+    free(gParsers);
+    gParsers = NULL;
+    gParserCount = 0;
+    gLispy = NULL;
+}
+
+lval* parse(mpc_ast_t *t) {
+    if (strstr(t->tag, "number")) {
+        errno = 0;
+        double_t d = strtod(t->contents, NULL);
+        return errno != 0 ? lval_err_detail(LERR_BAD_NUM, strerror(errno)) : lval_num(d);
+    }
+    if (strstr(t->tag, "ok")) {
+        return lval_ok();
+    }
+    if (strstr(t->tag, "symbol")) {
+        return lval_sym(t->contents);
+    }
+    if (strstr(t->tag, "string")) {
+        return parse_read_string(t);
+    }
+    
+    lval* result = NULL;
+    if (strcmp(t->tag, ">") == 0) { result = lval_s_expr(); } 
+    if (result == NULL && strstr(t->tag, "s_expr") != NULL)  { result = lval_s_expr(); }
+    if (result == NULL && strstr(t->tag, "q_expr") != NULL)  { result = lval_q_expr(); }
+
+    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 (strcmp(t->children[i]->tag,  "regex") == 0) { continue; }
+      if (strstr(t->children[i]->tag,  "comment") != NULL) { continue; }
+      result = lval_add(result, parse(t->children[i]));
+    }
+    return result;
+}
+lval* parse_read_string(mpc_ast_t* t) {
+    size_t tLen = strlen(t->contents);
+    //Copy string, excluding quote marks
+    char* unescaped = calloc(tLen, sizeof(char));
+    memcpy(unescaped, t->contents+sizeof(char), (tLen-2) * sizeof(char));
+    //evaluate entered escape characters. ie \n -> new line
+    unescaped = mpcf_unescape(unescaped);
+    
+    //return new string
+    lval* val = lval_str(unescaped);
+    free(unescaped);
+    return val;
+}
+
+lval* eval(lenv* env, lval* val) {
+    if (val->type == LVAL_SYM) {
+        lval* x = lenv_get(env, val);
+        lval_delete(val);
+        return x;
+    }
+    if (val->type == LVAL_S_EXPR) {
+        return eval_s_expr(env, val);
+    }
+    return val;
+}
+
+lval* eval_s_expr(lenv* env, lval* val) {
+    
+    //Eval children
+    for(int i = 0; i < val->cell_count; i++) {
+        val->cell_list[i] = eval(env, val->cell_list[i]);
+    }
+    
+    //Check for errors or exit
+    for(int i = 0; i < val->cell_count; i++) {
+        if (val->cell_list[i]->type == LVAL_ERR) {
+            return lval_take(val, i);
+        }
+        if (val->cell_list[i]->type == LVAL_EXIT) {
+            lval* exit = lval_copy(val->cell_list[i]);
+            lval_delete(val);
+            return exit;
+        }
+    }
+    
+    //empty
+    if (val->cell_count == 0) {
+        return val;
+    }
+    
+    //single
+    if (val->cell_count == 1) {
+        return lval_take(val, 0);
+    }
+    
+    //Ensure first is symbol
+    lval* func = lval_pop(val, 0);
+    if (func->type != LVAL_FUNC) {
+        VAL_TYPE type = func->type;
+        lval_delete(func); 
+        lval_delete(val);
+        return lval_err_detail(LERR_BAD_OP, "First element is not %s got %s", lval_str_name(LVAL_FUNC), lval_str_name(type));
+    }
+    
+    //Call builtin
+    lval* result = lval_call(env, func, val);
+    lval_delete(func);
+    return result;
+    
+}
\ No newline at end of file

lang.h

+#ifndef LANG_H
+#define	LANG_H
+
+// Set up the parser and related fuction
+
+#include "mpc.h"
+#include "lval.h"
+#include "lenv.h"
+#include "functions.h"
+#include "shared.h"
+    
+#define LASSERT(val, cond, errnum, errdetail, ...) \
+    if (!(cond)) { \
+        lval * err = lval_err_detail(errnum, errdetail, ##__VA_ARGS__); \
+        lval_delete(val); \
+        return err; \
+    }
+    
+#define LASSERT_TYPE(name, val, subject, expectedType) \
+    LASSERT(val, subject->type == expectedType, \
+            LERR_SYNTAX, "%s Expected type %s got %s", name, lval_str_name(expectedType), lval_str_name(subject->type))
+#define LASSERT_ARG_COUNT(name, val, subject, expectedNum) \
+    LASSERT(val, subject->cell_count == expectedNum, \
+            LERR_SYNTAX, "%s Expected %ld arguments got %ld", name, expectedNum, subject->cell_count )
+#define LASSERT_MIN_ARG_COUNT(name, val, subject, expectedNum) \
+    LASSERT(val, subject->cell_count >= expectedNum, \
+            LERR_SYNTAX, "%s Expected %ld or more arguments got %ld", name, expectedNum, subject->cell_count )
+    
+mpc_ast_t* tokenize(char *input);
+void setup_parsers();
+void cleanup_parsers();
+lval* parse(mpc_ast_t *t);
+lval* parse_read_string(mpc_ast_t* t);
+lval* eval(lenv* env, lval* val);
+lval* eval_s_expr(lenv* env, lval* val);
+
+#endif	/* LANG_H */
+

lenv.c

+#include <stdlib.h>
+
+#include "lang.h"
+#include "util.h"
+
+lenv* lenv_new() {
+    lenv* env = calloc(1, sizeof(lenv));
+    env->count = 0;
+    env->parent = NULL;
+    env->syms = NULL;
+    env->loaded_files_count = 0;
+    env->loaded_files = NULL;
+    return env;
+}
+void lenv_delete(lenv* env) {
+    for(int i = 0; i < env->count; i++) {
+        symtab_delete(env->syms[i]);
+    }
+    for(int i = 0; i < env->loaded_files_count; i++) {
+        free(env->loaded_files[i]);
+    }
+    if (env->loaded_files_count > 0) {
+        free(env->loaded_files);
+    }
+    if (env->syms != NULL) {
+        free(env->syms);
+    }
+    env->parent = NULL;
+    free(env);
+}
+lenv* lenv_copy(lenv* env) {
+    lenv* new = lenv_new();
+    new->parent = env;
+    new->syms = calloc(env->count, sizeof(symtab*));
+    for(int i = 0; i < env->count; i++) {
+        new->syms[i] = symtab_copy(env->syms[i]);
+    }
+    return new;
+}
+
+int lenv_compare_symtabs(const void *lhs, const void *rhs) {
+    const struct symtab* l = *(const struct symtab**)lhs;
+    const struct symtab* r = *(const struct symtab**)rhs;
+    
+    return strcmp(l->sym, r->sym);
+}
+
+void lenv_sort(lenv* env) {
+    qsort(env->syms, env->count, sizeof(symtab*), lenv_compare_symtabs);
+}
+
+symtab* lenv_search(lenv* env, char* sym) {
+    if (env->count == 0) {
+        return NULL;
+    }
+    symtab* searchElem = symtab_new(sym, NULL);
+    
+    symtab** searchComp = calloc(1, sizeof(symtab*));
+    searchComp[0] = searchElem;
+    
+    symtab** result = bsearch(searchComp, env->syms, env->count, sizeof(symtab*), lenv_compare_symtabs);
+    
+    free(searchComp);
+    symtab_delete(searchElem);
+    
+    if (result == NULL) {
+        return NULL;
+    }
+    return *result;
+}
+lenv* lenv_get_root(lenv* env) {
+    if (env->parent == NULL) {
+        return env;
+    } else {
+        return lenv_get_root(env->parent);
+    }
+}
+
+lval* lenv_get(lenv* env, lval* sym) {
+    LASSERT(sym, sym->type == LVAL_SYM, LERR_BAD_OP, "Expected symbol");
+    
+    symtab* result = lenv_search(env, sym->data.sym);
+    
+    if (result != NULL) {
+        return lval_copy(result->lval);
+    } else {
+        if (env->parent != NULL) {
+            return lenv_get(env->parent, sym);
+        } else {
+            return lval_err_detail(LERR_BAD_SYM, "Unbound Symbol '%s'", sym->data.sym);
+        }
+    }
+}
+
+void lenv_put(lenv* env, lval* key, lval* val) {
+    symtab* result = lenv_search(env, key->data.sym);
+    if (result != NULL) {
+        lval_delete(result->lval);
+        result->lval = lval_copy(val);
+        
+        lenv_sort(env);
+        return;
+    }
+    
+    env->count ++;
+    
+    env->syms = realloc(env->syms, sizeof(symtab*) * env->count);
+    
+    env->syms[env->count-1] = symtab_new(key->data.sym, val);
+    
+    lenv_sort(env);
+}
+void lenv_def(lenv* env, lval* key, lval* val) {
+    while(env->parent != NULL) {
+        env = env->parent;
+    }
+    lenv_put(env, key, val);
+}
+
+symtab* symtab_new(char* sym, lval* lval) {
+    symtab* new = calloc(1, sizeof(symtab));
+    new->lval = lval == NULL ? NULL : lval_copy(lval);
+    new->sym = strdup(sym);
+    return new;
+}
+void symtab_delete(symtab* symtab) {
+    if (symtab->lval != NULL) {
+        lval_delete(symtab->lval);
+    }
+    free(symtab->sym);
+    free(symtab);
+}
+symtab* symtab_copy(symtab* symtab) {
+    if (symtab == NULL) {
+        return NULL;
+    }
+    return symtab_new(symtab->sym, symtab->lval);
+}
\ No newline at end of file

lenv.h

+#ifndef LENV_H
+#define	LENV_H
+
+// define data structures and functions used for setting up environment
+ 
+struct lenv;
+typedef struct lenv lenv;
+    
+struct symtab;
+typedef struct symtab symtab;
+
+struct symtab {
+    char* sym;
+    lval* lval;
+};
+    
+struct lenv {
+    size_t count;
+    struct lenv* parent;
+    char** loaded_files;
+    size_t loaded_files_count;
+    struct symtab** syms;
+};
+
+lenv* lenv_new();
+void lenv_delete(lenv* env);
+lenv* lenv_copy(lenv* env);
+    
+int lenv_compare_symtabs(const void *a, const void *b);
+void lenv_sort(lenv* env);
+symtab* lenv_search(lenv* env, char* sym);
+lenv* lenv_get_root(lenv* env);
+    
+lval* lenv_get(lenv* env, lval* sym);
+void lenv_put(lenv* env, lval* key, lval* val);
+void lenv_def(lenv* env, lval* key, lval* val);
+void lenv_var(lenv* env, lval* key, lval* val);
+    
+symtab* symtab_new(char* sym, lval* lval);
+void symtab_delete(symtab* symtab);
+symtab* symtab_copy(symtab* symtab);
+
+#endif	/* LENV_H */
+

lval.c

+#include <stdlib.h>
+#include <float.h>
+#include <stdbool.h>
+
+#include "lang.h"
+#include "util.h"
+
+lval* lval_new(int type) {
+    lval* val = calloc(1,sizeof(lval));
+    val->type = type;
+    return val;
+}
+
+lval* lval_num(double_t x) {
+    lval* val = lval_new(LVAL_NUM);
+    val->data.num = x;
+    return val;
+}
+
+lval* lval_sym(char* x) {
+    lval* val = lval_new(LVAL_SYM);
+    val->data.sym = strdup(x);
+    return val;
+}
+
+lval* lval_s_expr() {
+    lval* val = lval_new(LVAL_S_EXPR);
+    val->cell_count = 0;
+    val->cell_list = NULL;
+    return val;
+}
+
+lval* lval_q_expr() {
+    lval* val = lval_new(LVAL_Q_EXPR);
+    val->cell_count = 0;
+    val->cell_list = NULL;
+    return val;
+}
+
+lval* lval_builtin(lbuiltin func, char* name) {
+    lval* val = lval_new(LVAL_FUNC);
+    val->data.func = calloc(1, sizeof(lval_func));
+    val->data.func->builtin = func;
+    val->data.func->name = strdup(name);
+    return val;
+}
+lval* lval_lambda(lval* formals, lval* body) {
+    lval* val = lval_new(LVAL_FUNC);
+    val->data.func = calloc(1, sizeof(lval_func));
+    val->data.func->builtin = NULL;
+    val->data.func->name = NULL;
+    val->data.func->env = lenv_new();
+    val->data.func->formals = formals;
+    val->data.func->body = body;
+    return val;
+}
+lval* lval_exit(short exitcode) {
+    lval* val = lval_new(LVAL_EXIT);
+    val->data.exitcode = exitcode;
+    return val;
+}
+lval* lval_str(char* str) {
+    lval* val = lval_new(LVAL_STR);
+    val->data.str = strdup(str);
+    return val;
+}
+lval* lval_ok() {
+    lval* val = lval_new(LVAL_OK);
+    return val;
+}
+
+lval* lval_add(lval* val, lval* x) {
+    val->cell_count++;
+    val->cell_list = realloc(val->cell_list, sizeof(lval*)*val->cell_count);
+    val->cell_list[val->cell_count-1] = x;
+    return val;
+}
+
+lval* lval_pop(lval* val, int index) {
+    //Get the item
+    lval* x = val->cell_list[index];
+    
+    //Re-create the list ignoring the index we are extracting
+    lval** newList = NULL;
+    if (val->cell_count-1 > 0) {
+        newList = calloc(val->cell_count-1, sizeof(lval*));
+        int k = 0;
+        for(int i=0; i < val->cell_count; i++) {
+            if (i == index) {
+                continue;
+            }
+            newList[k++] = val->cell_list[i];
+        }
+    }
+    
+    val->cell_count--;
+    free(val->cell_list);
+    val->cell_list = newList;
+    
+    return x;
+}
+
+lval* lval_take(lval* val, int i) {
+    lval* x = lval_pop(val, i);
+    lval_delete(val);
+    return x;
+}
+
+lval* lval_join(lval* a, lval* b) {
+    while(b->cell_count > 0) {
+        lval_add(a, lval_pop(b,0));
+    }
+    lval_delete(b);
+    return a;
+}
+
+lval* lval_call(lenv* env, lval* function, lval* args) {
+    lval_func* func = function->data.func;
+    
+    if (func->builtin != NULL) {
+        return func->builtin(env, args);
+    }
+    
+    //Check arg counts
+    LASSERT(args, func->formals->cell_count <= args->cell_count, LERR_SYNTAX,
+            "lambda: insufficient arguments. Expected %ld got %ld", func->formals->cell_count, args->cell_count);
+    
+    for(int i = 0; i < func->formals->cell_count; i++) {
+        lenv_put(func->env, func->formals->cell_list[i], args->cell_list[i]);
+    }
+    
+    if (func->va != NULL) {
+        lval* vaArgs = lval_q_expr();
+        
+        for(int i = func->formals->cell_count; i < args->cell_count; i ++ ) {
+            lval_add(vaArgs, lval_copy(args->cell_list[i]));
+        }
+        
+        lenv_put(func->env, func->va, vaArgs);
+        lval_delete(vaArgs);
+    }
+    
+    lval_delete(args);
+    
+    func->env->parent = env;
+    
+    return eval(func->env, lval_add(lval_s_expr(), lval_copy(func->body)));
+}
+
+bool lval_equal(lval* a, lval* b) {
+    if (a->type != b->type) {
+        return FALSE;
+    }
+    
+    switch(a->type) {
+        case LVAL_ERR:  return a->data.err.num == b->data.err.num;
+        case LVAL_NUM:  return fabs(a->data.num - b->data.num) <= DBL_EPSILON;
+        case LVAL_SYM:  return strcmp(a->data.sym, b->data.sym) == 0;
+        case LVAL_STR:  return strcmp(a->data.str, b->data.str) == 0;
+        case LVAL_OK:
+        case LVAL_EXIT:
+            return TRUE;
+        case LVAL_FUNC:
+            if (a->data.func->builtin != NULL) {
+                if (b->data.func->builtin != NULL) {
+                    return a->data.func->builtin == b->data.func->builtin;
+                } else {
+                    return FALSE;
+                }
+            } else {
+                if (b->data.func->builtin == NULL) {
+                    return FALSE;
+                } else {
+                    return lval_equal(b->data.func->formals, b->data.func->formals)
+                        && lval_equal(b->data.func->body, b->data.func->body);
+                }
+            }
+        case LVAL_Q_EXPR:
+        case LVAL_S_EXPR:
+            if (a->cell_count != b->cell_count) { return 0; }
+            for (int i = 0; i < a->cell_count; i++) {
+                if (!lval_equal(a->cell_list[i], b->cell_list[i])) {
+                    return FALSE;
+                }
+            }
+            return TRUE;
+            
+        default: return FALSE;
+    }
+}
+
+void lval_delete(lval* val) {
+    switch(val->type) {
+        case LVAL_NUM: break;
+        case LVAL_EXIT: break;
+        case LVAL_OK: break;
+        case LVAL_FUNC: 
+            if (val->data.func != NULL) {
+                if (val->data.func->builtin == NULL) {
+                    lenv_delete(val->data.func->env);
+                    lval_delete(val->data.func->formals);
+                    lval_delete(val->data.func->body);
+                } else {
+                    free(val->data.func->name);
+                }
+            }
+            break;
+        
+        case LVAL_SYM: free(val->data.sym); break;
+        case LVAL_STR: free(val->data.str); break;
+        case LVAL_ERR: 
+            if (val->data.err.detail != NULL) {
+                free(val->data.err.detail);
+            }
+            break;
+        case LVAL_Q_EXPR:
+        case LVAL_S_EXPR:
+            for (int i = 0; i < val->cell_count; i++) {
+                lval_delete(val->cell_list[i]);
+            }
+            if (val->cell_count > 0) {
+                free(val->cell_list);
+            }
+            break;
+    }
+    free(val);
+}
+
+lval* lval_copy(lval* current) {
+    lval* new = lval_new(current->type);
+    
+    switch(current->type) {
+        case LVAL_FUNC:
+            new->data.func = calloc(1, sizeof(lval_func));
+            lval_func* funcNew = new->data.func;
+            lval_func* funcCurrent = current->data.func;
+            
+            if (funcCurrent->builtin == NULL) {
+                funcNew->env = lenv_copy(funcCurrent->env);
+                funcNew->body = lval_copy(funcCurrent->body);
+                funcNew->formals = lval_copy(funcCurrent->formals);
+            } else {
+                funcNew->builtin = funcCurrent->builtin;
+                funcNew->name = strdup(funcCurrent->name);
+            }
+            break;
+        case LVAL_NUM: new->data.num = current->data.num; break;
+        case LVAL_EXIT: break;
+        case LVAL_OK: break;
+        
+        case LVAL_SYM: new->data.sym = strdup(current->data.sym); break;
+        case LVAL_STR: new->data.str = strdup(current->data.str); break;
+        case LVAL_ERR:
+            new->data.err.num = current->data.err.num;
+            new->data.err.detail = current->data.err.detail == NULL ? NULL : strdup(current->data.err.detail); 
+            break;
+        
+        case LVAL_Q_EXPR:
+        case LVAL_S_EXPR:
+            new->cell_count = current->cell_count;
+            if (new->cell_count == 0) {
+                new->cell_list = NULL;
+            } else {
+                new->cell_list = calloc(new->cell_count, sizeof(lval*));
+                for(int i=0; i < new->cell_count; i++) {
+                    new->cell_list[i] = lval_copy(current->cell_list[i]);
+                }
+            }
+            break;
+    }
+    
+    return new;
+}
+
+lval* lval_err(VAL_ERROR err){
+    return lval_err_detail(err, NULL);
+}
+
+lval* lval_err_detail(VAL_ERROR err, char* format, ...){
+    lval* val = lval_new(LVAL_ERR);
+    val->data.err.num = err;
+    
+    va_list va;
+    va_start(va, format);
+    
+    val->data.err.detail = calloc(512, sizeof(char));
+    
+    vsnprintf(val->data.err.detail, 511, format, va);
+    
+    if (strlen(val->data.err.detail) == 0) {
+        free(val->data.err.detail);
+        val->data.err.detail = NULL;
+    } else {
+        val->data.err.detail = realloc(val->data.err.detail, strlen(val->data.err.detail)+1);
+    }
+    
+    va_end(va);
+    
+    return val;
+}
+
+char* lval_str_name(VAL_TYPE type) {
+    switch(type) {
+        case LVAL_FUNC: return "Function";
+        case LVAL_NUM: return "Numeric";
+        case LVAL_STR: return "String";
+        case LVAL_SYM: return "Symbol";
+        case LVAL_Q_EXPR: return "Q-Expression";
+        case LVAL_S_EXPR: return "S-Expression";
+        case LVAL_EXIT: return "Exit";
+        case LVAL_ERR: return "Error";
+        case LVAL_OK: return "Ok/Success";
+        default: return "UNKNOWN";
+    }
+}
\ No newline at end of file

lval.h

+#ifndef LVAL_H
+#define	LVAL_H
+
+// Define structs representing lisp values and related functions. 
+// Forward declarations (if thats what they are called)
+struct lval;
+typedef struct lval lval;
+
+struct lval_func;
+typedef struct lval_func lval_func;
+
+#include <stdbool.h>
+#include "main.h"
+#include "lenv.h"
+
+#define LVAL_IS_TRUE(val) (val->type == LVAL_NUM && fabs(val->data.num) > DBL_EPSILON)
+#define LVAL_IS_FALSE(val) (val->type == LVAL_NUM && fabs(val->data.num) <= DBL_EPSILON)
+
+// LAVAL_SYM => symbol like '+'
+enum VAL_TYPE { LVAL_ERR, LVAL_NUM, LVAL_SYM, LVAL_FUNC, LVAL_S_EXPR, LVAL_Q_EXPR, LVAL_EXIT, LVAL_STR, LVAL_OK };
+enum VAL_ERROR { LERR_DIV_ZERO, LERR_BAD_OP, LERR_BAD_NUM, LERR_BAD_SYM, LERR_OTHER, LERR_SYNTAX, LERR_USER };
+typedef enum VAL_TYPE VAL_TYPE;
+typedef enum VAL_ERROR VAL_ERROR;
+
+typedef lval*(*lbuiltin)(lenv*, lval*);
+
+struct lval_func {
+    char* name;
+    lbuiltin builtin;
+    lenv* env;
+    lval* formals;
+    lval* body;
+    lval* va;
+};
+
+struct lval {
+  enum VAL_TYPE type;
+  union {
+     double_t num;
+     char* sym;
+     char* str;
+     short exitcode;
+     struct lval_func* func;
+     struct {
+        enum VAL_ERROR num;
+        char* detail;
+     } err;
+  } data;
+  
+  int cell_count;
+  struct lval** cell_list;
+  
+};
+
+// created corresponding lval
+lval* lval_new(int type);
+lval* lval_num(double_t x);
+lval* lval_sym(char* x);
+lval* lval_s_expr();
+lval* lval_q_expr();
+lval* lval_builtin(lbuiltin func, char* name);
+lval* lval_lambda(lval* formals, lval* body);
+lval* lval_exit(short exitcode);
+lval* lval_str(char* str);
+lval* lval_ok();
+
+lval* lval_add(lval* val, lval* x);
+lval* lval_pop(lval* val, int i);
+lval* lval_take(lval* val, int i);
+lval* lval_join(lval* a, lval* b);
+
+lval* lval_call(lenv* env, lval* function, lval* args);
+bool lval_equal(lval* a, lval* b);
+
+void lval_delete(lval* val);
+lval* lval_copy(lval* current);
+
+lval* lval_err(VAL_ERROR x);
+lval* lval_err_detail(VAL_ERROR x, char* format, ...);
+char* lval_str_name(VAL_TYPE type);
+
+#endif	/* LVAL_H */
+

main.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#include <editline/readline.h>
+
+#include "mpc.h"
+#include "lang.h"
+#include "main.h"
+#include "util.h"
+
+int main(int argc, char** argv) {
+    
+    printf("lixp Version %s\n", VERSION);
+    
+    // Init environment, add built-in
+    lenv* env = lenv_new();
+    lenv_add_builtin_funcs(env);
+    // Using shared variable in shared.c/h represents the parser
+    setup_parsers();
+    
+    //Attempt to import/run files specified on the command line
+    if (argc > 1) {
+        for(int i = 1; i < argc; i++) {
+            lval* loadargs = lval_add(lval_s_expr(), lval_str(argv[i]));
+            
+            lval* result = builtin_load(env, loadargs);
+            
+            if (result->type == LVAL_ERR) {
+                lval_println(result);
+            }
+            
+            lval_delete(result);
+        }
+    }
+    
+    int exitcode = EXIT_SUCCESS;
+    
+    while(1) {
+        char *input = readline("lixp> ");
+        if (NULL == input) {
+            break;
+        }
+        add_history(input);
+        
+        // tokenize the input
+        mpc_ast_t* ast_result = tokenize(input);
+        
+        free(input);
+        
+        if (ast_result != NULL) {
+            
+            //Parse the ast
+            lval* result = parse(ast_result);
+            if (result == NULL) {
+                result = lval_err(LERR_OTHER);
+            }
+            
+            //Evaluate
+            result = eval(env, result);
+            
+            BOOL exit = FALSE;
+            if (result != NULL && result->type == LVAL_EXIT) {
+                exit = TRUE;
+                exitcode = result->data.exitcode;
+            } else {
+                //print the result
+                lval_println(result);
+            }
+            
+            //Cleanup
+            lval_delete(result);
+            mpc_ast_delete(ast_result);
+            
+            if (exit == TRUE) {;
+                break;
+            }
+        }
+        
+    }
+    
+    lenv_delete(env);
+    cleanup_parsers();
+    
+    return (exitcode);
+}
+
+void lval_expr_print(lval* val, char* open, char* close) {
+    printf("%s", open);
+    
+    for(int i = 0; i < val->cell_count ; i++) {
+        lval_print(val->cell_list[i]);
+        
+        if (i != val->cell_count-1) {
+            putchar(' ');
+        }
+    }
+    
+    printf("%s", close);
+}
+
+void lval_print(lval* val) {
+    switch(val->type) {
+        case LVAL_NUM: printf("%g", val->data.num); break;
+        case LVAL_SYM: printf("%s", val->data.sym); break;
+        case LVAL_STR: lval_print_str(val); break;
+        case LVAL_S_EXPR: lval_expr_print(val, "(", ")"); break;
+        case LVAL_Q_EXPR: lval_expr_print(val, "{", "}"); break;
+        case LVAL_EXIT: printf("exit"); break;
+        case LVAL_OK: printf("ok"); break;
+        case LVAL_FUNC: ;
+            lval_func* func = val->data.func;
+            if (func->builtin != NULL) {
+                printf("<%s>", func->name);
+            } else {
+                printf("(<lambda> ");
+                lval_print(func->formals);
+                putchar(' ');
+                lval_print(func->body);
+                putchar(')');
+            }
+            break;
+        case LVAL_ERR:
+            switch(val->data.err.num) {
+                case LERR_DIV_ZERO: fprintf(stderr, "Divide By Zero"); break;
+                case LERR_BAD_NUM: fprintf(stderr,"Bad Number"); break;
+                case LERR_BAD_OP: fprintf(stderr,"Invalid Operator"); break;
+                case LERR_BAD_SYM: fprintf(stderr,"Unknown/Invalid Symbol"); break;
+                case LERR_OTHER: fprintf(stderr,"Unknown/Other Error"); break;
+                case LERR_SYNTAX: fprintf(stderr,"Syntax Error"); break;
+                case LERR_USER: fprintf(stderr,"Runtime Error"); break;
+                default: fprintf(stderr,"Unknown Error"); break;
+            }
+            if (val->data.err.detail != NULL) {
+                fprintf(stderr,": %s", val->data.err.detail);
+            }
+            break;
+    }
+}
+
+void lval_println(lval* val) {
+    lval_print(val);
+    putchar('\n');
+}
+
+void lval_print_str(lval* val) {
+    char* escaped = strdup(val->data.str);
+    escaped = mpcf_escape(escaped);
+    printf("\"%s\"", escaped);
+    free(escaped);
+}
\ No newline at end of file

main.h

+#ifndef MAIN_H
+#define	MAIN_H
+    
+#define VERSION "0.0.0.1"
+    
+typedef unsigned char BOOL;
+    
+#define TRUE 1
+#define FALSE 0
+
+int main(int argc, char** argv);
+
+void lval_expr_print(lval* val, char* open, char* close);
+void lval_print(lval* val);
+void lval_println(lval* val);
+void lval_print_str(lval* val);
+
+#endif	/* MAIN_H */
+

makefile

+CC = gcc
+
+lixp: main.c functions.c lang.c lenv.c lval.c mpc.c shared.c util.c
+	$(CC) -Wall --std=c99  main.c functions.c lang.c lenv.c lval.c mpc.c shared.c util.c -ledit -lm -o lixp
\ No newline at end of file

shared.c

+#include <stdlib.h>
+#include "shared.h"
+
+#include "mpc.h"
+
+mpc_parser_t* gLispy = NULL;
+size_t gParserCount = 0;
+mpc_parser_t** gParsers = NULL;
\ No newline at end of file

shared.h

+#ifndef SHARED_H
+#define	SHARED_H
+    
+#include "mpc.h"
+
+// shared variables
+    
+extern mpc_parser_t* gLispy;
+extern size_t gParserCount;
+extern mpc_parser_t** gParsers;
+
+#endif	/* SHARED_H */
+

test.lixp

+(def {hello} "Hello World")
+hello

util.c

+#include <string.h>
+#include <stdlib.h>
+#include <stdarg.h>
+
+#include "util.h"
+
+char * strdup(const char* s) {
+    if (s == NULL) return NULL;
+    char *d = calloc(strlen (s) + 1, sizeof(char));
+    if (d == NULL) return NULL;
+    strcpy (d,s);
+    return d;
+}
+
+char* vstrcat(int n, ...) {
+    va_list va;
+    
+    char** strings = calloc(n, sizeof(char*));
+    size_t stringLength = 0;
+    
+    va_start(va, n);
+    
+    for(int i = 0; i<n; i++) {
+        strings[i] = va_arg(va, char*);
+        stringLength += strlen(strings[i]);
+    }
+    
+    va_end(va);
+    
+    char* newStr = calloc(stringLength+1, sizeof(char));
+    
+    for(int i = 0; i<n; i++) {
+        strcat(newStr, strings[i]);
+    }
+    
+    free(strings);
+    
+    return newStr;
+}
\ No newline at end of file

util.h

+#ifndef UTIL_H
+#define	UTIL_H
+
+char* strdup(const char* s);
+char* vstrcat(int n, ...);
+
+#endif	/* UTIL_H */
+