improvement: added round/1 and round/2 to expressions

documentation/topics/expressions.md

@@ -47,6 +47,8 @@ The following functions are built in:
 - `string_split/2` | As above, but with a specific delimiter
 - `string_split/3` | As above, but with options. See the function for the available options.
 - `at/2` | Get an element from a list, i.e `at(list, 1)`
+- `round/1` | Round a float, decimal or int to 0 precision, i.e `round(num)`
+- `round/2` | Round a float, decimal or int to the provided precision or less, i.e `round(1.1234, 3) == 1.1234` and `round(1.12, 3) == 1.12`
 
 ## Sub-expressions
 

lib/ash/filter/filter.ex

@@ -29,6 +29,7 @@ defmodule Ash.Filter do
     Length,
     Minus,
     Now,
+    Round,
     StringJoin,
     StringSplit,
     Today,
@@ -61,6 +62,7 @@ defmodule Ash.Filter do
     Length,
     Minus,
     Now,
+    Round,
     Today,
     Type,
     StringJoin,

lib/ash/query/function/round.ex

@@ -0,0 +1,27 @@
+defmodule Ash.Query.Function.Round do
+  @moduledoc """
+  Rounds a float, decimal or integer to the given number of points
+  """
+
+  use Ash.Query.Function, name: :round
+
+  def args,
+    do: [
+      [:float, :integer],
+      [:decimal, :integer],
+      [:integer, :integer],
+      [:float],
+      [:decimal],
+      [:integer]
+    ]
+
+  def evaluate(%{arguments: [num]} = round), do: evaluate(%{round | arguments: [num, 0]})
+  def evaluate(%{arguments: [num, _]}) when is_integer(num), do: {:known, num}
+
+  def evaluate(%{arguments: [num, precision]}) when is_float(num),
+    do: {:known, Float.round(num, precision)}
+
+  def evaluate(%{arguments: [num, precision]}) do
+    {:known, num |> Decimal.round(precision) |> Decimal.normalize()}
+  end
+end