diff --git a/src/pebblisp.c b/src/pebblisp.c
index 2699a4e..4255110 100644
--- a/src/pebblisp.c
+++ b/src/pebblisp.c
@@ -9,86 +9,6 @@
 #define printf(...) APP_LOG(APP_LOG_LEVEL_DEBUG, __VA_ARGS__)
 #endif
 
-void copySlice(char * dest, struct Slice *src)
-{
-    if(!dest || !src)
-        return;
-    strncpy(dest, src->text, src->length);
-    dest[(int)src->length] = '\0';
-}
-
-void debugSlice(struct Slice *s)
-{
-    if(!s) {
-        printf("NULL SLICE\n");
-        return;
-    }
-    printf("Debug Slice\n    text:'");
-    for(int i = 0; i < s->length; i++) {
-        printf("%c", s->text[i]);
-        if(s->text[i] == '\0')
-            printf("NULLCHAR\n");
-    }
-    printf("'\n");
-    printf("  length: %d\n", s->length);
-}
-
-Result parse(struct Slice *slices)
-{
-    struct Slice *token = slices;
-    if(token && token->text) {
-        struct Slice *rest = &slices[1];
-        if(token->text[0] == '(') {
-            // todo check for null rest
-            return readSeq(rest);
-        } else { // todo error on missing close paren
-            return result(parseAtom(token), rest);
-        }
-    } else {
-        return result(errorObject(NULL_PARSE), NULL);
-    }
-}
-
-Result readSeq(struct Slice *tokens)
-{
-    Object res = listObject();
-    for(;;) {
-        struct Slice *next = tokens;
-        struct Slice *rest = next->text? &next[1] : NULL;
-        if(next->text[0] == ')') {
-            return result(res, rest);
-        }
-        Result r = parse(tokens);
-        nf_addToList(&res, r.obj);
-        tokens = r.slices;
-    }
-}
-
-Object parseAtom(struct Slice *s)
-{
-    if(isDigit(s->text[0])) {
-        int num = 0;
-        for(int i = 0; i < s->length; i++) {
-            num *= 10;
-            num += s->text[i] - '0';
-        }
-        return numberObject(num);
-
-    } else if (s->text[0] == 'T' && s->length == 1) {
-        return boolObject(1);
-
-    } else if (s->text[0] == 'F' && s->length == 1) {
-        return boolObject(0);
-
-    } else if (s->text[0] == '"') {
-        return objFromSlice(s->text, s->length);
-    } else {
-        Object o = symbolObject();
-        copySlice(o.name, s);
-        return o;
-    }
-}
-
 Object evalDefArgs(const Object *arg_forms, struct Environment *env)
 {
     const Object *newSymbol = arg_forms;
@@ -261,13 +181,16 @@ Object catObjects(const Object obj1, const Object obj2, struct Environment *env)
     return o;
 }
 
-Object _basicOp(const Object *obj1, const Object *obj2, const char op)
+Object _basicOp(const Object *obj1, const Object *obj2, const char op,
+                struct Environment *env)
 {
     const int n1 = obj1->number;
     const int n2 = obj2->number;
 
     switch(op){
         case '+':
+            if(obj1->type == TYPE_STRING || obj2->type == TYPE_STRING)
+                return catObjects(*obj1, *obj2, env);
             return numberObject(n1 + n2);
         case '-':
             return numberObject(n1 - n2);
@@ -294,7 +217,7 @@ Object basicOp(const Object *obj1, const Object *obj2, const char op,
 {
     int lists = (obj1->type == TYPE_LIST) + (obj2->type == TYPE_LIST);
     if(lists == 0) {
-        return _basicOp(obj1, obj2, op);
+        return _basicOp(obj1, obj2, op, env);
 
     } else if(lists == 1) { // Single operand is applied to each element in list
         const Object *listObj = (obj1->type == TYPE_LIST)? obj1 : obj2;
@@ -303,7 +226,7 @@ Object basicOp(const Object *obj1, const Object *obj2, const char op,
         Object newList = listObject();
         FOR_POINTER_IN_LIST(listObj) {
             Object adding = eval(POINTER, env);
-            nf_addToList(&newList, _basicOp(&adding, singleObj, op));
+            nf_addToList(&newList, _basicOp(&adding, singleObj, op, env));
         }
         return newList;
 
@@ -313,7 +236,7 @@ Object basicOp(const Object *obj1, const Object *obj2, const char op,
             FOR_POINTERS_IN_LISTS(obj1, obj2) {
                 const Object ev1 = eval(P1, env);
                 const Object ev2 = eval(P2, env);
-                nf_addToList(&newList, _basicOp(&ev1, &ev2, op));
+                nf_addToList(&newList, _basicOp(&ev1, &ev2, op, env));
             }
             return newList;
         } else {
@@ -337,6 +260,86 @@ BASIC_OP(lth, '<');
 
 #undef BASIC_OP
 
+void copySlice(char * dest, struct Slice *src)
+{
+    if(!dest || !src)
+        return;
+    strncpy(dest, src->text, src->length);
+    dest[(int)src->length] = '\0';
+}
+
+void debugSlice(struct Slice *s)
+{
+    if(!s) {
+        printf("NULL SLICE\n");
+        return;
+    }
+    printf("Debug Slice\n    text:'");
+    for(int i = 0; i < s->length; i++) {
+        printf("%c", s->text[i]);
+        if(s->text[i] == '\0')
+            printf("NULLCHAR\n");
+    }
+    printf("'\n");
+    printf("  length: %d\n", s->length);
+}
+
+Result parse(struct Slice *slices)
+{
+    struct Slice *token = slices;
+    if(token && token->text) {
+        struct Slice *rest = &slices[1];
+        if(token->text[0] == '(') {
+            // todo check for null rest
+            return readSeq(rest);
+        } else { // todo error on missing close paren
+            return result(parseAtom(token), rest);
+        }
+    } else {
+        return result(errorObject(NULL_PARSE), NULL);
+    }
+}
+
+Result readSeq(struct Slice *tokens)
+{
+    Object res = listObject();
+    for(;;) {
+        struct Slice *next = tokens;
+        struct Slice *rest = next->text? &next[1] : NULL;
+        if(next->text[0] == ')') {
+            return result(res, rest);
+        }
+        Result r = parse(tokens);
+        nf_addToList(&res, r.obj);
+        tokens = r.slices;
+    }
+}
+
+Object parseAtom(struct Slice *s)
+{
+    if(isDigit(s->text[0])) {
+        int num = 0;
+        for(int i = 0; i < s->length; i++) {
+            num *= 10;
+            num += s->text[i] - '0';
+        }
+        return numberObject(num);
+
+    } else if (s->text[0] == 'T' && s->length == 1) {
+        return boolObject(1);
+
+    } else if (s->text[0] == 'F' && s->length == 1) {
+        return boolObject(0);
+
+    } else if (s->text[0] == '"') {
+        return objFromSlice(s->text, s->length);
+    } else {
+        Object o = symbolObject();
+        copySlice(o.name, s);
+        return o;
+    }
+}
+
 Object parseEval(const char *input, struct Environment *env)
 {
     struct Slice *tokens = nf_tokenize(input);
diff --git a/src/tests.sh b/src/tests.sh
index 5ba1a63..cea3b16 100755
--- a/src/tests.sh
+++ b/src/tests.sh
@@ -76,6 +76,10 @@ check "FbnciSeq" "(def fib (fn (a) \
                   ))) \
                   (fib 20)" "6765"
 echo ""
+check "ExplicitCat" "(cat \"Big\" \" Kitty\")" "Big Kitty"
+check "CatNums" "(cat \"There are \" (+ 2 3) \" kitties\")" "There are 5 kitties"
+check "ImplicitCat" "(+ \"There are \" (* 5 4) \" bonks\")" "There are 20 bonks"
+check "CatAssocLeft" "(+ 10 20 \" rascals\")" "30 rascals"
 
 if [ "$FAILS" -ne "0" ]; then
         echo "$FAILS Tests Failed"