Add reduce

README.md

@@ -147,6 +147,12 @@ Zap.chunk(['a', 'b', 'c', 4], 2) # [['a', 'b'], ['c', 4]]
   array # [3, 2, 1]
   ```
 
+* `reduce(array, func)` - Combines all elements in the collection by applying a binary operation, specified by a block, so as to reduce them to a single value
+
+  ```crystal
+  Zap.reduce([1, 2, 3], -> (acc: Int32, element: Int32) {acc + element}) # 6
+  ```
+
 * `sorted_uniq(array)` - Sort array and returns a new array by removing duplicate values in self
 
   ```crystal

spec/zap_spec.cr

@@ -103,6 +103,12 @@ describe Zap do
     )
   end
 
+  it "@reduce Combines all elements in the collection by applying a binary operation, specified by a block, so as to reduce them to a single value" do
+    Zap.reduce([1, 2, 3], ->(acc : Int32, element : Int32) { acc + element }).should eq(
+      6
+    )
+  end
+
   it "@reverse Reverses array so that the first element becomes the last, the second element becomes the second to last, and so on" do
     array = [1, 2, 3]
 

src/zap.cr

@@ -169,6 +169,10 @@ module Zap
   def remove
   end
 
+  def reduce(array, func)
+    array.reduce { |acc, i| func.call(acc, i) }
+  end
+
   def reverse(array)
     array.reverse!
   end
@@ -285,9 +289,6 @@ module Zap
   def every
   end
 
-  def filter
-  end
-
   def find
   end
 
@@ -330,9 +331,6 @@ module Zap
   def partition
   end
 
-  def reduce
-  end
-
   def reduce_right
   end