feat: nil/null/empty/blank literals, resolves #102

src/drop/empty-drop.ts

@@ -0,0 +1,27 @@
+import { Drop } from './drop'
+import { IComparable } from './icomparable'
+import { isObject, isString, isArray } from 'src/util/underscore'
+import { IDrop } from 'src/drop/idrop'
+
+export class EmptyDrop extends Drop implements IDrop, IComparable {
+  equals (value: any) {
+    if (isString(value) || isArray(value)) return value.length === 0
+    if (isObject(value)) return Object.keys(value).length === 0
+    return false
+  }
+  gt () {
+    return false
+  }
+  geq () {
+    return false
+  }
+  lt () {
+    return false
+  }
+  leq () {
+    return false
+  }
+  value () {
+    return ''
+  }
+}