rest is [“a”] and last_gift is “b”. rest |> Enum.join(", “) returns “a”, which is a string. “a” |> “#{}, and #{last_gift}” returns “a, and b”. But when I pipe them together, I get ArgumentError. rest |> Enum.join(”, ") |> “#{}, and #{last_gift}” ** (ArgumentError) argument error What do I miss…

You cannot pipe a variable into a string. iex> last = "b" iex> x = "a" iex> "a" |> "#{}, and #{last}" "a, and b" iex> x |> "#{}, and #{last}" ** (ArgumentError) argument error But You can iex> "#{x}, and #{last}" "a, and b" My guess is a string is not a function, and does accept only “”…

[image] kokolegorille: You cannot pipe a variable into a string. Ha! That’s spot on! Thanks!

It turns out a |> "#{}" doesn’t mean we are actually interpolating a into the position of #{} iex(71)> "a" |> "This is: #{}, and #{last}" "aThis is: , and b" iex(72)> "a" |> "This is: , and #{last}" "aThis is: , and b"

It does not mean it’s piping a string into a string either… iex> "aa" |> "bb" ** (ArgumentError) cannot pipe "aa" into "bb", can only pipe into local calls foo(), remote calls Foo.bar() or anonymous functions calls foo.() (elixir) lib/macro.ex:156: Macro.pipe/3 (stdlib) lists.erl:1263: :lis…

ah, yeah… I wonder if it’s actually a bug now… :point_down: doesn’t seem to be an intended behavior, then… iex(72)> "a" |> "This is: , and #{last}" "aThis is: , and b"

Underneath, it’s iex> quote do: "aa" |> "bb#{}" {:|>, [context: Elixir, import: Kernel], [ "aa", {:<<>>, [], [ "bb", {:::, [], [ {{:., [], [Kernel, :to_string]}, [], [{:__block__, [], []}]}, {:binary, [], Elixir} ]} ]} ]}

Right, so "234#{five}" is actually <<"234", five::binary>>, which is invoking Kernel.SpecialForms.<<>>. Piping something into that prepends the value at the front of that binary, if it is a legal parameter to <<>>. So in the end "1" |> "234#{five}" expands to <<"1", "234", five::binary>> which happ…

Didn’t know about quote until now. Seems super useful, thanks! That explains the ArgumentError: iex(84)> x = "a" "a" iex(85)> quote do: "bb#{x}" {:<<>>, [], [ "bb", {:::, [], [ {{:., [], [Kernel, :to_string]}, [], [{:x, [], Elixir}]}, {:binary, [], Elixir} ]} ]} iex(86)>…

You actually kind of may pipe a variable into the string interpolation if it’s wrapped into the anonymous function call, like "test" |> (&"shmest #{&1}").() Looks ugly though.