diff --git a/.gitignore b/.gitignore
index 77f2048..ab9ba69 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 tags
 *.un~
+/foobar
diff --git a/cig.h b/cig.h
index 4535a15..5e7af07 100644
--- a/cig.h
+++ b/cig.h
@@ -170,7 +170,7 @@ void *dyn_array_create_func(dyn_array_create_func_args_t args);
 		.line = __LINE__, \
 		.allocator = __VA_ARGS__, \
 	}); \
-} while(0);
+} while(0)
 
 // Always reassign the array. if multiple variables reference the same growing
 // array, then you should be using pointer pointers.
@@ -278,10 +278,10 @@ void *map_create_func(map_create_func_args_t args);
 		.line=__LINE__, \
 		.allocator=__VA_ARGS__ \
 	}); \
-} while(0);
+} while(0)
 
 #define init_set(PTR, ...) do { \
-	(*(PTR)) = map_create_func(map_create_func_args_t) { \
+	(*(PTR)) = map_create_func((map_create_func_args_t) { \
 		.item_size=sizeof(*(*(PTR))), \
 		.key_size=sizeof(*(*(PTR))), \
 		.key_offset=0, \
@@ -289,7 +289,7 @@ void *map_create_func(map_create_func_args_t args);
 		.line=__LINE__, \
 		.allocator=__VA_ARGS__ \
 	}); \
-} while(0);
+} while(0)
 
 int map_len(void *this);
 int map_cap(void *this);
@@ -297,6 +297,28 @@ uint32_t fnv_1a(const uint8_t *bytes, const unsigned int size);
 // Used for debugging the mapping array. Prints out nerdfonts icons to indicate
 // the state of each mapping slot.
 void map_print_mapping_state(void *this, FILE *file);
+// Checks that the map can handle one more item. The maps capacity grows if not,
+// usually by doubling the capacity.
+void map_assure_growable_by_1(void **this, const char *file, int line);
+
+typedef struct index_pair {
+	unsigned int new_index;
+	unsigned int old_index;
+	bool has_old_index;
+} index_pair_t;
+/*
+ * Hashes modulo the header->mapping_capacity. Will linearly probe until a free
+ * slot is found. If the key already exists in the mapping array, that will be
+ * indicated in the return value, and the user is expected to overwrite the old
+ * index with a tombstone if they are going to write a new value for that key.
+ */
+index_pair_t map_pair_hash(void *this, void *pair);
+
+// TODO: NOT DONE
+#define map_add(THIS, PAIR) do { \
+	map_assure_growable_by_1(THIS, __FILE__, __LINE__); \
+	index_pair_t idx_pair = map_pair_hash((*(THIS)), pair); \
+} while (0)
 
 // CLI /////////////////////////////////////////////////////////////////////////
 
diff --git a/foobar.c b/foobar.c
new file mode 100644
index 0000000..218c802
--- /dev/null
+++ b/foobar.c
@@ -0,0 +1,12 @@
+#define CIG_IMPL
+#include "cig.h"
+
+int main() {
+	with_borrow(allocator) {
+		int *ints;
+		init_set(&ints, allocator, .initial_capacity=20);
+		map_print_mapping_state(ints, stdout);
+		set_add(ints, 10);
+		map_print_mapping_state(ints, stdout);
+	}
+}
diff --git a/justfile b/justfile
index ab443b5..213bc7e 100644
--- a/justfile
+++ b/justfile
@@ -5,6 +5,17 @@ TESTBIN := "/tmp/all_tests"
 
 set shell := ["bash", "-cu"]
 
+FOOBAR := "foobar"
+
+run_foobar: build_foobar
+    ./{{FOOBAR}}
+
+build_foobar:
+    {{CC}} ./foobar.c -o {{FOOBAR}}
+
+clean_foobar:
+    rm {{FOOBAR}}
+
 test: build
 	{{TESTBIN}}
 
diff --git a/map.c b/map.c
index 7e9ef99..de93db7 100644
--- a/map.c
+++ b/map.c
@@ -16,6 +16,13 @@
 #define DEFAULT ESC "0m"
 #define COLORED(COLOR, TEXT) COLOR TEXT DEFAULT
 
+static int internal_map_mod(int a, int b) {
+    int r = a % b;
+    if (r < 0) r += (b > 0 ? b : -b);
+    return r;
+}
+#define mod(a, b) internal_map_mod(a, b)
+
 void map_print_mapping_state(void *this, FILE *file) {
 	map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
 	for ( int i = 0; i < header->mapping_capacity; i++ ) {
@@ -89,12 +96,6 @@ void *map_create_func(
 	return header->bytes;
 }
 
-typedef struct index_pair {
-	unsigned int new_index;
-	unsigned int old_index;
-	bool has_old_index;
-} index_pair_t;
-
 static const void *internal_cig_key_ptr_from_pair_ptr(const void *this, const void *pair) {
 	map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
 	return (const void *) &((const char *)pair)[header->key_offset];
@@ -116,12 +117,24 @@ bool map_key_equals(void *this, const void *key1, const void *key2) {
 	return true;
 }
 
-/*
- * Hashes modulo the header->mapping_capacity. Will linearly probe until a free
- * slot is found. If the key already exists in the mapping array, that will be
- * indicated in the return value, and the user is expected to overwrite the old
- * index with a tombstone if they are going to write a new value for that key.
- */
+int map_place(void *this, index_pair_t idx_pair) {
+	map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
+	if (idx_pair.has_old_index) {
+		header->mapping_arr[idx_pair.new_index] = header->mapping_arr[idx_pair.old_index];
+		header->mapping_arr[idx_pair.old_index] = FLAG_TOMBSTONE;
+		for ( long i = idx_pair.old_index; i != idx_pair.new_index; mod(i-1, header->mapping_capacity) ) {
+			if (header->mapping_arr[i] == FLAG_TOMBSTONE) {
+				header->mapping_arr[i] = FLAG_FREE;
+			} else {
+				break;
+			}
+		}
+	}
+	// TODO WRONG!!!
+
+	return idx_pair.new_index;
+}
+
 index_pair_t map_pair_hash(void *this, void *pair) {
 	map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
 	const void *key = internal_cig_key_ptr_from_pair_ptr(this, pair);
@@ -184,8 +197,6 @@ index_pair_t map_pair_hash(void *this, void *pair) {
 	}
 }
 
-// Checks that the map can handle one more item. The maps capacity grows if not,
-// usually by doubling the capacity.
 void map_assure_growable_by_1(void **this, const char *file, int line) {
 	map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, *this);
 	unsigned int new_n_items = header->n_items + 1;