From fecf3f19c393b0d79fd653db399271a9037cc782 Mon Sep 17 00:00:00 2001
From: Don Alfons Nisnoni <donnisnoni.tid3@gmail.com>
Date: Tue, 8 Oct 2019 18:23:17 +0800
Subject: [PATCH] array: add filter() method

---
 .gitignore                |  1 +
 vlib/builtin/array.v      | 25 +++++++++++++++++++++++++
 vlib/builtin/array_test.v | 24 ++++++++++++++++++++++--
 3 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index d6a836f4ac..b7fb1d2d09 100644
--- a/.gitignore
+++ b/.gitignore
@@ -29,3 +29,4 @@ vjs
 # Thumbnails
 ._*
 .vrepl_temp.v
+a.out
diff --git a/vlib/builtin/array.v b/vlib/builtin/array.v
index f0bff62c93..7eeb86f586 100644
--- a/vlib/builtin/array.v
+++ b/vlib/builtin/array.v
@@ -329,3 +329,28 @@ pub fn (a []char) index(v char) int {
 	}
 	return -1
 }
+
+////////////// FILTER //////////////
+
+// Creates a new array with all elements that pass the test implemented by the provided function.
+pub fn (a  []string) filter(predicate fn(p_val string, p_i int, p_arr []string) bool) []string
+{
+	mut res := []string
+	for i := 0; i < a.len; i++  {
+		if predicate(a[i], i, a) {
+			res << a[i]
+		}
+	}
+	return res
+}
+
+pub fn (a []int) filter(predicate fn(p_val int, p_i int, p_arr []int) bool) []int
+{
+	mut res := []int
+	for i := 0; i < a.len; i++  {
+		if predicate(a[i], i, a) {
+			res << a[i]
+		}
+	}
+	return res
+}
diff --git a/vlib/builtin/array_test.v b/vlib/builtin/array_test.v
index 9ba751236c..2b528908cb 100644
--- a/vlib/builtin/array_test.v
+++ b/vlib/builtin/array_test.v
@@ -286,7 +286,7 @@ fn test_multi() {
 	// TODO
 	//b :=  [ [[1,2,3],[4,5,6]], [[1,2]] ]
 	//assert b[0][0][0] == 1
-}	
+} 
 
 fn test_in() {
 	a := [1,2,3]
@@ -295,4 +295,24 @@ fn test_in() {
 	assert 3 in a
 	assert !(4 in a)
 	assert !(0 in a)
-}	
+} 
+
+fn callback_1(val int, index int, arr []int) bool {
+	return val >= 2
+}
+
+fn callback_2(val string, index int, arr []string) bool {
+	return val.len >= 2
+}
+
+fn test_filter() {
+	a := [1, 2, 3, 4, 5, 6]
+	b := a.filter(callback_1)
+	assert b[0] == 2
+	assert b[1] == 3
+
+	c := ['v', 'is', 'awesome']
+	d := c.filter(callback_2)
+	assert d[0] == 'is'
+	assert d[1] == 'awesome'
+}