Scryer-prolog: Compilation fails on MacOS

[dcnorris]

Following a conversation with @triska, this issue is intended to bubble up my earlier comment which perhaps (?) got submerged as #706 was merged.

I remain unable to install on MacOS Catalina 10.15.7 following these instructions:

cargo install scryer-prolog --no-default-features --features num

   Compiling select v0.4.3
   Compiling sodiumoxide v0.2.6
error[E0463]: can't find crate for `rug`
  --> /Users/david/.cargo/registry/src/github.com-1ecc6299db9ec823/scryer-prolog-0.8.127/src/main.rs:24:1
   |
24 | extern crate rug;
   | ^^^^^^^^^^^^^^^^^ can't find crate

error: aborting due to previous error

For more information about this error, try `rustc --explain E0463`.
error: failed to compile `scryer-prolog v0.8.127`, intermediate artifacts can be found at `/var/folders/pb/d6v8rn4j6x10bzx8qfrs6w6w0000gn/T/cargo-installS0kSlT`

Caused by:
  could not compile `scryer-prolog`.

[notoria]

Try this:

$ git clone https://github.com/mthom/scryer-prolog
$ cd scryer-prolog
$ cargo install scryer-prolog --no-default-features --features num --path .

With --path ., it should work.

[triska]

@dcnorris: In addition to what @notoria explained, you can use the latest version of Scryer Prolog by compiling it from source with:

$> git clone https://github.com/mthom/scryer-prolog
$> cd scryer-prolog
$> cargo run --release

obtaining the executable scryer-prolog/target/release/scryer-prolog.

[dcnorris]

I can confirm that both @notoria's and @triska's suggestions work (with --no-default-features --features num --path . understood appended in the latter case). Closing, thanks.