Shift

Author: langsamu

src/ListItem.ts

@@ -78,4 +78,23 @@ export class ListItem<T> extends TermWrapper {
             yield more
         }
     }
+
+    shift(): T | undefined {
+        const rest = this.rest
+        if (!rest.isListItem) {
+            throw new Error("?")
+        }
+
+        const shifted = this.first
+        const nextFirst = rest.firstRaw
+        const nextRest = rest.restRaw
+
+        rest.firstRaw = undefined
+        rest.restRaw = undefined
+
+        this.firstRaw = nextFirst
+        this.restRaw = nextRest
+
+        return shifted
+    }
 }

src/RdfList.ts

@@ -129,7 +129,11 @@ export class RdfList<T> implements Array<T> {
     }
 
     shift(): T | undefined {
-        throw new Error("not implemented")
+        for (const item of this.items) {
+            return item.shift()
+        }
+
+        return undefined
     }
 
     slice(start?: number, end?: number): T[] {

test/unit/rdf_list.test.ts

@@ -146,4 +146,60 @@ describe("RDF List", () => {
             assert.deepStrictEqual([...wrapper.list], ["o1", "o2", "o3"])
         })
     })
+
+    describe("shift", () => {
+        it("not list undefined", () => {
+            const rdf = `<s> <p> <o> .`
+            const wrapper = new Wrapper("s", datasetFromRdf(rdf), DataFactory)
+
+            const shifted = wrapper.list.shift()
+
+            assert.strictEqual(shifted, undefined)
+        })
+
+        it("empty undefined", () => {
+            const rdf = `<s> <p> () .`
+            const wrapper = new Wrapper("s", datasetFromRdf(rdf), DataFactory)
+
+            const shifted = wrapper.list.shift()
+
+            assert.strictEqual(shifted, undefined)
+        })
+
+        it("one returns first", {skip: "not implemented yet"}, () => {
+            const rdf = `<s> <p> ( "o1" ) .`
+            const wrapper = new Wrapper("s", datasetFromRdf(rdf), DataFactory)
+
+            const shifted = wrapper.list.shift()
+
+            assert.strictEqual(shifted, "o1")
+        })
+
+        it("one shrinks", {skip: "not implemented yet"}, () => {
+            const rdf = `<s> <p> ( "o1" ) .`
+            const wrapper = new Wrapper("s", datasetFromRdf(rdf), DataFactory)
+
+            wrapper.list.shift()
+
+            assert.deepStrictEqual([...wrapper.list], [])
+        })
+
+        it("two returns first", () => {
+            const rdf = `<s> <p> ( "o1" "o2" ) .`
+            const wrapper = new Wrapper("s", datasetFromRdf(rdf), DataFactory)
+
+            const shifted = wrapper.list.shift()
+
+            assert.strictEqual(shifted, "o1")
+        })
+
+        it("two shrinks", () => {
+            const rdf = `<s> <p> ( "o1" "o2" ) .`
+            const wrapper = new Wrapper("s", datasetFromRdf(rdf), DataFactory)
+
+            wrapper.list.shift()
+
+            assert.deepStrictEqual([...wrapper.list], ["o2"])
+        })
+    })
 })