refactor and improve primitiveJoin()

1 files changed, 88 insertions, 19 deletions

diff --git a/liblali.c b/liblali.c
index c2ec974..6696bc3 100644
--- a/liblali.c
+++ b/liblali.c
@@ -1112,30 +1112,99 @@ Object *primitiveJoin(Object **args, GC_PARAM) {
   if ((*args)->car == nil)
     exception("cannot join an empty list");
 
+  // check if the list argument is indeed a list
+  if ((*args)->car->type != TYPE_CONS)
+    exceptionWithObject((*args)->car, "must be a list");
+
+  // determine what is the result type
+  int resType = (*args)->car->car->type;
+  if (isSplittedNumber((*args)->car))
+    resType = TYPE_NUMBER;
+  else if (resType != TYPE_STRING &&
+           resType != TYPE_SYMBOL)
+    exceptionWithObject((*args)->car, "cannot be joined");
+
+  // check that there are only symbols or strings
+  // also get the size for result string
+  unsigned long long size = 0;
+  Object *list = (*args)->car;
+  if (resType == TYPE_STRING)
+    for (;;) {
+      if (list->car->type != TYPE_SYMBOL &&
+          list->car->type != TYPE_STRING )
+        exceptionWithObject((*args)->car,
+                            "can only have first-level elements of or symbols or strings");
+
+      size += strlen(list->car->string);
+      if (list->cdr == nil) break;
+      list = list->cdr;
+    }
+  else if (resType == TYPE_SYMBOL)
+    for (;;) {
+      if (list->car->type != TYPE_SYMBOL)
+        exceptionWithObject((*args)->car, "can only have first-level elements of symbol");
+
+      size += strlen(list->car->string);
+      if (list->cdr == nil) break;
+      list = list->cdr;
+    }
+  else if (resType == TYPE_NUMBER) {
+    Object *lcar = nil;
+    ++size;
+    list = list->cdr;
+
+    for (;;) {
+      lcar = list->car;
+      for (;;) {
+        ++size; // just use the first digit
+        if (lcar->cdr == nil) break;
+        lcar = lcar->cdr;
+      }
+
+      if (list->cdr == nil) break;
+      ++size;
+      list = list->cdr;
+    }
   }
-  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) {
-      wordLength = strlen(tmpCons->cdr->car->string);
-      for (j = 0; j < wordLength; j++)
-        symbolResult[i+j] = tmpCons->cdr->car->string[j];
-      i += j;
+
+  char result[size+1];  // +1 for '\0'
+
+  // copy to result string
+  list = (*args)->car;
+  strcpy(result, list->car->string);
+  char noPrefixNumber[2];
+
+  if (resType == TYPE_NUMBER) {
+    Object *lcar = nil;
+    list = list->cdr;
+    for (;;) {
+      lcar = list->car;
+      for (;;) {
+        noPrefixNumber[0] = lcar->car->string[1];
+        noPrefixNumber[1] = '\0';
+        strcat(result, noPrefixNumber);
+
+        if (lcar->cdr == nil) break;
+        lcar = lcar->cdr;
+      }
+
+      if (list->cdr == nil) break;
+      strcat(result, ".");
+      list = list->cdr;
     }
+    return newNumber(result, GC_ROOTS);
   }
-  symbolResult[i] = '\0';
 
-  if (elementsType == TYPE_STRING)
-    return newString(symbolResult, GC_ROOTS);
+  for (; list->cdr != nil; list = list->cdr)
+    strcat(result, list->cdr->car->string);
+
+  // the return
+  if (resType == TYPE_STRING)
+    return newString(result, GC_ROOTS);
+  else if (resType == TYPE_SYMBOL)
+    return newSymbol(result, GC_ROOTS);
   else
-    return newSymbol(symbolResult, GC_ROOTS);
+    exception("this join error should not happen");
 }
 
 Object *primitiveSplit(Object **args, GC_PARAM) {