Everything seems to be correct. So no idea from here. Does it work for other functions just fine?
josevalim
Creator of Elixir
chrismcg
map comes from the Basic Types in https://hexdocs.pm/elixir/master/typespecs.html#types-and-their-syntax and has a () in the docs there so I’m surprised is isn’t added by the language formatter. (As an aside I don’t get why types are made to look like function calls, including the ones I create myself)
From reading the docs .formatter.exs isn’t going to help with Logger.info is it? (Haven’t tried yet).
0
Eiji
@[quote=“josevalim, post:14, topic:11064”]
Everything seems to be correct. So no idea from here. Does it work for other functions just fine?
[/quote]
I found a problem. This does not work when:
- I copy module directly into
iexshell and call this function - Module and call to it are in same file (just call function directly after module declaration)
Both rules applies to normal guards and defguard. Is it expected?
Firstly I through that I have something broken. 
0
josevalim
Creator of Elixir
No, it won’t. Those will always have parens.
Yup! We need to locate the .beam file in disk in order to the blaming, which means it won’t be available in IEx nor in the middle of compilation.
1
Eiji
@josevalim: Thank you very much!
Last question (related to previous - see “My current version”):
Do you think that defguard could help me short my code?
Here is a old, but full version that uses macros:
defmodule Example do
defmacro is_rgb_integer(integer) do
quote do
unquote(integer) in 0..255
end
end
defmacro is_rgb_strict(rgb) do
quote do
Example.is_rgb_integer(elem(unquote(rgb), 0)) and
Example.is_rgb_integer(elem(unquote(rgb), 1)) and
Example.is_rgb_integer(elem(unquote(rgb), 2))
end
end
defmacro is_css_alpha(alpha) do
quote do
unquote(alpha) >= 0 and unquote(alpha) <= 1
end
end
defmacro is_rgba(rgba) do
quote do
tuple_size(unquote(rgba)) == 4 and Example.is_rgb_strict(unquote(rgba)) and
Example.is_css_alpha(elem(unquote(rgba), 3))
end
end
defmacro is_rgb(rgba) do
quote do
(tuple_size(unquote(rgba)) == 3 and Example.is_rgb_strict(unquote(rgba))) or
(tuple_size(unquote(rgba)) == 4 and Example.is_rgb_strict(unquote(rgba)) and
Example.is_css_alpha(elem(unquote(rgba), 3)))
end
end
end
It would be awesome if it will be possible to somehow declare guards with pattern matching in future - just like in function head.
0
josevalim
Creator of Elixir
This should work:
defmodule Example do
defguard is_rgb_integer(integer) when integer in 0..255
defguard is_rgb_strict(rgb)
when is_rgb_integer(elem(rgb, 0)) and
is_rgb_integer(elem(rgb, 1)) and
is_rgb_integer(elem(rgb, 2))
defguard is_css_alpha(alpha) when alpha >= 0 and alpha <= 1
defguard is_rgba(rgba)
when tuple_size(rgba) == 4 and is_rgb_strict(rgba) and is_css_alpha(elem(rgba, 3))
defguard is_rgb(rgba)
when (tuple_size(rgba) == 3 and is_rgb_strict(rgba)) or
(tuple_size(rgba) == 4 and is_rgb_strict(rgba))
end
1
Eiji
Unfortunately not. 
iex(1)> require Example
Example
iex(2)> Example.is_rgb({255, 255})
** (CompileError) iex:2: undefined function is_rgb_strict/1
(stdlib) lists.erl:1354: :lists.mapfoldl/3
(stdlib) lists.erl:1354: :lists.mapfoldl/3
(elixir) expanding macro: Kernel.and/2
I tried it myself similarly too, but I can’t call defguard inside defguard.
0
josevalim
Creator of Elixir
Can you please open up a bug report? I am almost sure we have a test case for this, so I need to investigate exactly what is happening here.
0
Eiji
@josevalim: Done.
For all interested more info in #7147: Could not call defguard check inside defguard. issue.
Update: Bug confirmed and fixed in 6aadfba586b22b22550e9d839a3c89d27224579b commit.
4
Eiji
@josevalim: Sorry for ping you again, but I don’t understand why I got same warning (I corrected my guards).
Full code
defmodule Example do
defguardp is_rgb_integer(tuple, index) when elem(tuple, index) in 0..255
defguardp is_rgb_base(rgb)
when is_rgb_integer(rgb, 0) and is_rgb_integer(rgb, 1) and is_rgb_integer(rgb, 2)
defguard is_css_alpha(alpha) when alpha >= 0 and alpha <= 1
defguardp is_rba_css_alhpa(tuple) when tuple |> elem(3) |> is_css_alpha()
defguard is_rgba(rgba)
when is_tuple(rgba) and tuple_size(rgba) == 4 and is_rgb_base(rgba) and
is_rba_css_alhpa(rgba)
defguard is_rgb(rgba)
when is_tuple(rgba) and
(tuple_size(rgba) == 3 or (tuple_size(rgba) == 4 and is_rba_css_alhpa(rgba))) and
is_rgb_base(rgba)
end
My changes were to make some guards private and don’t called twice, but I’m getting this: warning: this expression will fail with ArgumentError
Minimal example
I wrote smaller example that generates same error:
defmodule Example do
defguard test_me(rgba)
when is_tuple(rgba) and
( # comment this
tuple_size(rgba) == 4
and elem(rgba, 3) == :ok
) # comment this
end
# and in another file:
require Example
Example.test_me({1, 2})
Now try to comment lines with ( and ) characters (as in comments) and recompile project. Warning will not appear now.
Is it a bug too?
0