Add table.slice & table.countvalues

src/ltablib.cpp

@@ -820,10 +820,73 @@ static int tkeys (lua_State *L) {
 }
 
 
+static int tcountvalues (lua_State *L) {
+  luaL_checktype(L, 1, LUA_TTABLE);
+
+  lua_newtable(L);
+  lua_pushnil(L);
+  while (lua_next(L, 1)) { /* og, result, key */
+    if (!lua_isnoneornil(L, 4)) { /* if the value isn't nil */
+      lua_pushvalue(L, 4); /* push the key, prepare for result[value] */
+      lua_gettable(L, 2); /* push result[value] */
+      const lua_Integer i = luaL_optinteger(L, -1, 0) + 1; /* start or update count */
+      lua_pushvalue(L, 4); /* push the key again */
+      lua_pushinteger(L, i); /* push updated count */
+      lua_settable(L, 2); /* update result */
+    }
+
+    lua_settop(L, 3); /* reset stack to og, result, key */
+  }
+
+  return 1;
+}
+
+
+static int tslice (lua_State *L) {
+  luaL_checktype(L, 1, LUA_TTABLE);
+
+  lua_Integer idx_start = luaL_checkinteger(L, 2);
+  lua_Integer idx_end = luaL_checkinteger(L, 3);
+  const lua_Integer l = luaL_len(L, 1);
+
+  if (idx_start < 0) {
+    idx_start = l + idx_start + 1;
+  }
+
+  if (idx_end < 0) {
+    idx_end = l + idx_end + 1;
+  }
+  else if (idx_end > l) {
+    idx_end = l;
+  }
+
+  lua_newtable(L);
+  lua_Integer idx_result = 1;
+  for (lua_Integer i = idx_start; i <= idx_end; ++i) {
+    lua_pushinteger(L, i);
+    lua_gettable(L, 1);
+    if (!lua_isnoneornil(L, -1)) {
+      lua_pushinteger(L, idx_result++);
+      lua_pushvalue(L, -2);
+      lua_settable(L, 4);
+    }
+    else {
+      lua_pop(L, 1);
+    }
+  }
+
+  lua_settop(L, 4);
+
+  return 1;
+}
+
+
 /* }====================================================== */
 
 
 static const luaL_Reg tab_funcs[] = {
+  {"slice", tslice},
+  {"countvalues", tcountvalues},
   {"keys", tkeys},
   {"modget", modget},
   {"modset", modset},

testes/pluto/basic.pluto

@@ -1952,6 +1952,77 @@ do
     assert(keys:contains("b"))
     assert(keys:contains("c"))
 end
+do
+    local test_table_1 = {1, 2, 2, 3, 1}
+    local counts_1 = test_table_1:countvalues()
+    assert(counts_1[1] == 2)
+    assert(counts_1[2] == 2)
+    assert(counts_1[3] == 1)
+
+    local test_table_2 = {1, 2, nil, 3, 1, nil}
+    local counts_2 = test_table_2:countvalues()
+    assert(counts_2[1] == 2)
+    assert(counts_2[2] == 1)
+    assert(counts_2[3] == 1)
+
+    local test_table_3 = {1, 2, 3, 4, 5}
+    local counts_3 = test_table_3:countvalues()
+    assert(counts_3[1] == 1)
+    assert(counts_3[2] == 1)
+    assert(counts_3[3] == 1)
+    assert(counts_3[4] == 1)
+    assert(counts_3[5] == 1)
+
+    local test_table_4 = {1, "hello", 1, "world", "hello"}
+    local counts_4 = test_table_4:countvalues()
+    assert(counts_4[1] == 2)
+    assert(counts_4["hello"] == 2)
+    assert(counts_4["world"] == 1)
+
+    local test_table_5 = {}
+    local counts_5 = test_table_5:countvalues()
+    assert(next(counts_5) == nil)
+
+    local test_table_6 = {1, {2}, 1, {2}, 3}
+    local counts_6 = test_table_6:countvalues()
+    for key, value in counts_6 do
+        if type(key) == "table" then
+            assert(value == 1)
+            continue
+        elseif key == 1 then
+            assert(value == 2)
+            continue
+        elseif key == 3 then
+            assert(value == 1)
+            continue
+        end
+        error()
+    end
+
+    local test_table_7 = { 1, 2, 3, 2, 3, 3, 4, test_table_6, nil, test_table_6 }:countvalues()
+    assert(test_table_7[1] == 1)
+    assert(test_table_7[2] == 2)
+    assert(test_table_7[3] == 3)
+    assert(test_table_7[4] == 1)
+    assert(test_table_7[test_table_6] == 2)
+end
+do
+    local t = {1, 2, 3, 4, 5}
+
+    assert(table.slice(t, 1, 3)[1] == 1)
+    assert(table.slice(t, 1, 3)[2] == 2)
+    assert(table.slice(t, 1, 3)[3] == 3)
+    assert(#table.slice(t, 1, 3) == 3)
+
+    assert(table.slice(t, -3, -1)[1] == 3)
+    assert(table.slice(t, -3, -1)[2] == 4)
+    assert(table.slice(t, -3, -1)[3] == 5)
+    assert(#table.slice(t, -3, -1) == 3)
+
+    assert(#table.slice(t, 6, 10) == 0)
+    assert(#table.slice(t, 2, 10) == 4)
+    assert(#table.slice(t, 0, 10) == #t)
+end
 do
     assert(compareversions("0.1.0", "0.1.0") == 0)
     assert(compareversions("0.1.0", "0.2.0") ~= 0)