Exceptions!!!

src/list.c

@@ -1,6 +1,10 @@
 #include "list.h"
 
 #include "function.h"
+#include "stack.h"
+
+DEFINE_SYMBOL(circular_list_error, "circular-list-error");
+DEFINE_CONDITION_CLASS(circular_list_error, error);
 
 intptr_t list_length(LispVal *list) {
     assert(LISTP(list));
@@ -32,21 +36,24 @@ DEFUN(cons, "cons", (LispVal * car, LispVal *cdr), "(car cdr)",
 }
 
 DEFUN(length, "length", (LispVal * list), "(list)", "") {
-    // TODO type check
-    // TODO list may be circular
-    return MAKE_FIXNUM(list_length(list));
+    CHECK_LISTP(list);
+    intptr_t len = list_length(list);
+    if (len == -1) {
+        lisp_signal(Qcircular_list_error, Qnil);
+    }
+    return MAKE_FIXNUM(len);
 }
 
 DEFUN(length_eq, "length=", (LispVal * list, LispVal *length), "(list length)",
       "Return non-nil if LIST's length is LENGTH.") {
-    // TODO type check
+    CHECK_LISTP(list);
     return list_length_eq(list, XFIXNUM(length)) ? Qt : Qnil;
 }
 
 DEFUN(nreverse, "nreverse", (LispVal * list), "(list)", "") {
-    // TODO type checking
     LispVal *rev = Qnil;
     while (!NILP(list)) {
+        CHECK_LISTP(list);
         LispVal *next = XCDR(list);
         RPLACD(list, rev);
         rev = list;
@@ -63,6 +70,22 @@ DEFUN(list, "list", (LispVal * args), "(&rest args)", "") {
     return args;
 }
 
+LispVal *nth(size_t n, LispVal *list) {
+    size_t i = 0;
+    DOTAILS(rest, list) {
+        if (i == n) {
+            return XCAR(rest);
+        }
+        ++i;
+    }
+    return Qnil;
+}
+
+DEFUN(nth, "list", (LispVal * n, LispVal *list), "(n list)", "") {
+    CHECK_TYPE(n, TYPE_FIXNUM);
+    return nth(XFIXNUM(n), list);
+}
+
 DEFUN(member, "member", (LispVal * elt, LispVal *list, LispVal *pred),
       "(elt list &optional pred)", "") {
     if (NILP(pred) || pred == Qeq) {
@@ -74,7 +97,7 @@ DEFUN(member, "member", (LispVal * elt, LispVal *list, LispVal *pred),
         }
     } else {
         DOTAILS(rest, list) {
-            if (CALL(pred, elt, XCAR(rest))) {
+            if (!NILP(CALL(pred, elt, XCAR(rest)))) {
                 return rest;
             }
         }
@@ -82,6 +105,16 @@ DEFUN(member, "member", (LispVal * elt, LispVal *list, LispVal *pred),
     return Qnil;
 }
 
+DEFUN(member_if, "member-if", (LispVal * pred, LispVal *list), "(pred list)",
+      "") {
+    DOTAILS(rest, list) {
+        if (!NILP(CALL(pred, XCAR(rest)))) {
+            return rest;
+        }
+    }
+    return Qnil;
+}
+
 DEFUN(plist_put, "plist-put", (LispVal * plist, LispVal *prop, LispVal *value),
       "(plist prop value)", "") {
     CHECK_LISTP(plist);