list.findIndex()

docs/docs/collections/lists.md

@@ -285,14 +285,30 @@ By default the initial value for `.reduce()` is 0, however we can change this to
 print(["Dictu ", "is", " great!"].reduce(def (accumulate, element) => accumulate + element, "")); // 'Dictu is great!'
 ```
 
-### list.find(func)
+### list.find(func, number: start -> optional, number: end -> optional)
 
 To find a single item within a list we use `.find()`. Find will search through each item in the list and as soon as the
 callback returns a truthy value, the item that satisfied the callback is returned, if none of the items satisfy the callback
-function then `nil` is returned.
+function then `nil` is returned. The optional start and end parameters change the points at which the list will be searched.
 
 Note: The first item to satisfy the callback is returned.
 
 ```cs
 print([1, 2, 3].find(def (item) => item == 2)); // 2
+print([1, 2, 3, 4, 5, 6].find(def (item) => item % 2 == 0, 2)); // 4
+print([1, 2, 3, 4, 5, 6].find(def (item) => item % 2 == 0, 2, 3)); // nil
+```
+
+### list.findIndex(func, number: start -> optional, number: end -> optional)
+
+To find a single item within a list we use `.findIndex()`. Find will search through each item in the list and as soon as the
+callback returns a truthy value, the index at which the item that satisfied the callback is returned, if none of the items satisfy the callback
+function then `nil` is returned. The optional start and end parameters change the points at which the list will be searched.
+
+Note: The first item to satisfy the callback is returned.
+
+```cs
+print([1, 2, 3].findIndex(def (item) => item == 2)); // 1
+print([1, 2, 3, 4, 5, 6].findIndex(def (item) => item % 2 == 0, 2)); // 3
+print([1, 2, 3, 4, 5, 6].findIndex(def (item) => item % 2 == 0, 2, 3)); // nil
 ```

src/vm/datatypes/lists/list-source.h

@@ -43,11 +43,19 @@
 "    }\n" \
 "}\n" \
 "\n" \
-"def find(list, func) {\n" \
-"    for (var i = 0; i < list.len(); i += 1) {\n" \
+"def find(list, func, start=0, end=list.len()) {\n" \
+"    for (var i = start; i < end; i += 1) {\n" \
 "        if (func(list[i])) {\n" \
 "            return list[i];\n" \
 "        }\n" \
 "    }\n" \
 "}\n" \
+"\n" \
+"def findIndex(list, func, start=0, end=list.len()) {\n" \
+"    for (var i = start; i < end; i += 1) {\n" \
+"        if (func(list[i])) {\n" \
+"            return i;\n" \
+"        }\n" \
+"    }\n" \
+"}\n" \
 

src/vm/datatypes/lists/list.du

@@ -43,10 +43,18 @@ def forEach(list, func) {
     }
 }
 
-def find(list, func) {
-    for (var i = 0; i < list.len(); i += 1) {
+def find(list, func, start=0, end=list.len()) {
+    for (var i = start; i < end; i += 1) {
         if (func(list[i])) {
             return list[i];
         }
     }
+}
+
+def findIndex(list, func, start=0, end=list.len()) {
+    for (var i = start; i < end; i += 1) {
+        if (func(list[i])) {
+            return i;
+        }
+    }
 }

tests/lists/find.du

@@ -10,4 +10,8 @@
 const myList = [1, 2, 3, 4, 5];
 
 assert(myList.find(def (item) => item == 3) == 3);
-assert(myList.find(def (item) => item == 10) == nil);
+assert(myList.find(def (item) => item == 10) == nil);
+assert(myList.find(def (item) => item % 2 == 0) == 2);
+assert(myList.find(def (item) => item % 2 == 0, 2) == 4);
+assert(myList.find(def (item) => item % 2 == 0, 2, 3) == nil);
+assert(myList.find(def (item) => item % 2 == 0, 5) == nil);

tests/lists/findIndex.du

@@ -0,0 +1,17 @@
+/**
+ * find.du
+ *
+ * Testing the list.findIndex() method
+ *
+ * .findIndex() runs a user defined function on each element in the list and returns the index of the item in the
+ * list that satisfies the callback
+ */
+
+const myList = [1, 2, 3, 4, 5];
+
+assert(myList.findIndex(def (item) => item == 3) == 2);
+assert(myList.findIndex(def (item) => item == 10) == nil);
+assert(myList.findIndex(def (item) => item % 2 == 0) == 1);
+assert(myList.findIndex(def (item) => item % 2 == 0, 2) == 3);
+assert(myList.findIndex(def (item) => item % 2 == 0, 2, 3) == nil);
+assert(myList.findIndex(def (item) => item % 2 == 0, 5) == nil);

tests/lists/import.du

@@ -24,4 +24,5 @@ import "filter.du";
 import "reduce.du";
 import "forEach.du";
 import "find.du";
+import "findIndex.du";
 import "reverse.du";