add Enum.product(_by)

Author: superruzafa

assets/images/functions/Enum/product-1.tex

@@ -0,0 +1,13 @@
+\matrix [list=a] {
+  \node [index=1]; &
+  \node [index=2]; &
+  \node [elements between]; &
+  \node [index=n]; \\
+};
+
+\draw [brace] (an.south east) -- (a1.south west);
+
+\draw [->] (last brace) -- +(0, -1)
+  node [below]
+  {$a_1 \cdot a_2 \cdot \dots \cdot a_n = \displaystyle\prod_{i=1}^n a_i$};
+ 

assets/images/functions/Enum/product_by-2.tex

@@ -0,0 +1,22 @@
+\matrix [list=a] {
+  \node [index=1]; &
+  \node [index=2]; &
+  \node [elements between]; &
+  \node [index=n]; \\
+};
+
+\foreach \i in {1,2,n}{
+    \node (fun\i) [fun, below=.5 of a\i.south];
+    \draw [->] (a\i.south) -- (fun\i.in);
+    \draw [->] (fun\i.out) -- +(0, -.5)
+        node (b\i) [below] {$b_{\i}$};
+};
+
+
+
+\draw [brace] (bn.south east) -- (b1.south west);
+
+\draw [->] (last brace) -- +(0, -1)
+  node [below]
+  {$b_1 \cdot b_2 \cdot \dots \cdot b_n = \displaystyle\prod_{i=1}^n b_i$};
+ 

content/en/functions/Enum/product-1.md

@@ -0,0 +1,10 @@
+---
+title: product_by/2
+url: Enum/product_by/2
+---
+
+Returns the product of all elements of `enumerable`.
+
+Raises `ArithmeticError` if `enumerable` contains a non-numeric value.
+
+{{< figure src="images/functions/Enum/product_by-2.svg" >}}

content/en/functions/Enum/product_by-2.md

@@ -0,0 +1,10 @@
+---
+title: product_by/2
+url: Enum/product_by/2
+---
+
+Maps and computes the product of the given `enumerable` in one pass.
+
+Raises `ArithmeticError` if `fun` returns a non-numeric value.
+
+{{< figure src="images/functions/Enum/product_by-2.svg" >}}

data/signatures.yaml

@@ -254,6 +254,16 @@
             empty_fallback \\ fn -> raise Enum.EmptyError end
           )
         end
+    - name: product/1
+      signature: |
+        defmodule Enum do
+          def product(enumerable)
+        end
+    - name: product_by/2
+      signature: |
+        defmodule Enum do
+          def product_by(enumerable, fun)
+        end
     - name: random/1
       signature: |
         defmodule Enum do