Add tap/1

Shamelessy stolen and adopted from @hayleigh-dot-dev and https://hexdocs.pm/elixir/main/Kernel.html#tap/2

1 files changed, 10 insertions, 1 deletions

diff --git a/src/gleam/function.gleam b/src/gleam/function.gleam
index 5aebb76..007eded 100644
--- a/src/gleam/function.gleam
+++ b/src/gleam/function.gleam
@@ -52,9 +52,18 @@ pub fn identity(x: a) -> a {
   x
 }
 
-/// A function that takes a single argument and returns a new function that
+/// Takes a single argument and returns a new function that
 /// ignores its argument and always returns the input value.
 ///
 pub fn constant(value: a) -> fn(b) -> a {
   fn(_) { value }
 }
+
+/// Takes a function with a single argument
+/// calls that function with that argument 
+/// and returns that argument instead of the function return value.
+/// Useful for running synchronous side effects in a pipeline.
+pub fn tap (arg, effect: fn (a) -> b) -> a {
+  effect(arg)
+  arg
+}