From cd75e60fb94ee76d1dc58a1a8f624eefb93b1372 Mon Sep 17 00:00:00 2001
From: Brandon Rozek <rozekbrandon@gmail.com>
Date: Thu, 7 Jun 2018 20:33:56 -0400
Subject: [PATCH] Added builtin init functionality for Q-expressions

---
 lval/expressions.c | 17 +++++++++++++++--
 lval/expressions.h |  8 ++++++--
 prompt.c           |  1 +
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/lval/expressions.c b/lval/expressions.c
index 3c4f579..77fc9e3 100644
--- a/lval/expressions.c
+++ b/lval/expressions.c
@@ -85,16 +85,29 @@ lval* lval_eval_sexpr(lval* v) {
 }
 
 
-lval* builtin_head(lval* a) {
+lval* builtin_headn(lval* a, int n) {
 	LASSERT(a, a->count == 1, "Function 'head' passed too many arguments")
 	LASSERT(a, a->cell[0]->type == LVAL_QEXPR, "Function 'head' passed incorrect type")
 	LASSERT(a, a->cell[0]->count != 0, "Function 'head' passed {}")
 
 	lval* v = lval_take(a, 0);
-	while (v->count > 1) { lval_del(lval_pop(v, 1)); }
+	while (v->count > n) { lval_del(lval_pop(v, v->count - 1)); }
 	return v;
 }
 
+lval* builtin_head(lval* a) {
+	return builtin_headn(a, 1);
+}
+
+lval* builtin_init(lval* a) {
+	LASSERT(a, a->count == 1, "Function 'init' passed too many arguments")
+	LASSERT(a, a->cell[0]->type == LVAL_QEXPR, "Function 'init' passed incorrect type")
+	LASSERT(a, a->cell[0]->count != 0, "Function 'init' passed {}")
+
+	return builtin_headn(a, a->cell[0]->count - 1);
+}
+
+
 lval* builtin_tail(lval* a) {
 	LASSERT(a, a->count == 1, "Function 'tail' passed too many arguments")
 	LASSERT(a, a->cell[0]->type == LVAL_QEXPR, "Function 'tail' passed incorrect type")
diff --git a/lval/expressions.h b/lval/expressions.h
index 9bda991..5893a01 100644
--- a/lval/expressions.h
+++ b/lval/expressions.h
@@ -24,13 +24,17 @@ lval* lval_eval_sexpr(lval* v);
 
 /*
     QEXPR Operations
-    Head: Takes a Q-Expression and returns a Q-Expression with only of the first element
+    Head: Takes a Q-Expression and returns a Q-Expression with only the first element
     Tail: Takes a Q-Expression and returns a Q-Expression with the first element removed
     List: Takes one or more arguments and returns a new Q-Expression containing the arguments
     Eval: Takes a Q-Expression and evaluates it as if it were a S-Expression
-    Join:  join	Takes one or more Q-Expressions and returns a Q-Expression of them conjoined together
+    Join: Takes one or more Q-Expressions and returns a Q-Expression of them conjoined together
+    Len:  Takes a Q-Expression and returns the length of the Q-Expression
+    Init: Takes a Q-Expression and returns a Q-Expression with only the last element removed   
 */
+lval* builtin_headn(lval* a, int n);
 lval* builtin_head(lval* a);
+lval* builtin_init(lval* a);
 lval* builtin_tail(lval* a);
 lval* builtin_list(lval* a);
 lval* builtin_eval(lval* a);
diff --git a/prompt.c b/prompt.c
index 9a5d647..eb08752 100644
--- a/prompt.c
+++ b/prompt.c
@@ -169,6 +169,7 @@ lval* builtin(lval* a, char* func) {
 	if (strcmp("join", func) == 0) { return builtin_join(a); }
 	if (strcmp("eval", func) == 0) { return builtin_eval(a); }
 	if (strcmp("len", func) == 0) { return builtin_len(a); }
+	if (strcmp("init", func) == 0) { return builtin_init(a); }
 	if (strstr("+-/*^%", func)) { return builtin_op(a, func); }
 	if (strcmp("min", func) == 0) { return builtin_op(a, func); }
 	if (strcmp("max", func) == 0) { return builtin_op(a, func); }