1 files changed, 13 insertions, 5 deletions

diff --git a/liblali.c b/liblali.c
index 7394ca3..ac552c2 100644
--- a/liblali.c
+++ b/liblali.c
@@ -1041,19 +1041,23 @@ Object *primitiveJoin(Object **args, GC_PARAM) {
     exceptionWithObject((*args)->car, "is not a list");
 
   Object *tmpCons = (*args)->car;
+
+  int elementsType = tmpCons->car->type;
+
   unsigned long i = strlen(tmpCons->car->string);
-  for (; tmpCons->cdr != nil; tmpCons = tmpCons->cdr)
+  for (; tmpCons->cdr != nil; tmpCons = tmpCons->cdr) {
     i += strlen(tmpCons->cdr->car->string);
-
+    if (elementsType != tmpCons->cdr->car->type)
+      exception("cannot join list atoms of different type");
+  }
   char symbolResult[i+1];
+
   tmpCons = (*args)->car;
   unsigned long wordLength = strlen(tmpCons->car->string);
   unsigned long j = 0;
-
   // first list element
   for (; j < wordLength; j++)
       symbolResult[j] = tmpCons->car->string[j];
-
   // rest of list elements
   if (tmpCons->cdr->car != nil) {
     for (i = wordLength; tmpCons->cdr != nil; tmpCons = tmpCons->cdr) {
@@ -1064,7 +1068,11 @@ Object *primitiveJoin(Object **args, GC_PARAM) {
     }
   }
   symbolResult[i] = '\0';
-  return newSymbol(symbolResult, GC_ROOTS);
+
+  if (elementsType == TYPE_STRING)
+    return newString(symbolResult, GC_ROOTS);
+  else
+    return newSymbol(symbolResult, GC_ROOTS);
 }
 
 typedef struct Primitive {