What do the backslashes do in this Gosu code?

Question

I'm not too deep in Gosu, so this code confused me. I've googled, etc., but to no avail. What are the backslashes doing in this snippet?

GET_STUFF.execute(\ -> {
      var gig = withPackagedGig(request.id, request.signature, \ k -> {
        k.addItem("Log_RetrievedGig");
        return k;
      });
      myObj = toObj(gig);
    })

Possible duplicate of [Line continuation characters in JavaScript](https://stackoverflow.com/questions/10514873/line-continuation-characters-in-javascript) — the_storyteller, Feb 26 '19 at 15:19
@the_storyteller, but there wouldn't be characters *after* the line continuation character, would there? — Jonathan M, Feb 26 '19 at 15:20
Yeah, this wouldn't compile in java 8 (obviously not 8, `var`), but I'm not sure the backslash would work here as intended in pure java. It would qualify as an illegal character — Rogue, Feb 26 '19 at 15:20
This is not valid Java syntax in any Java version so far. Something else must be processing it before the compiler and using the backslashes to escape the spaces for some reason. — Michael, Feb 26 '19 at 15:21
I misread the question, thinking it was Javascript. That _is_ valid Javascript. — the_storyteller, Feb 26 '19 at 15:21
@Michael, good to know. I'll go back to the person that provided it. Thanks. — Jonathan M, Feb 26 '19 at 15:21
@the_storyteller, good to know. What would the backslashes do in this code if it were javascript? — Jonathan M, Feb 26 '19 at 15:22
@JonathanM, then it would be a line continuation character (see possible duplicate answer.) It isn't necessary for line continuation, but is valid syntax. — the_storyteller, Feb 26 '19 at 15:23
@the_storyteller, ah, yes, I thought you were referring to a different use. It definitely could be line continuation in js, but it wouldn't make sense for there to be characters after the slash in that case. I'm guessing this is somehow corrupted Java (as the provider said it was Java, and it has typed variables elsewhere, along with annotations). — Jonathan M, Feb 26 '19 at 15:25
Which version of Java? The use of `var` means it's either Java 10 (very new), or it's Javascript. — the_storyteller, Feb 26 '19 at 15:26
As you all suspected, it's not pure Java, but a custom variant called Gosu: https://gosu-lang.github.io/. I've updated the tags. — Jonathan M, Feb 26 '19 at 15:30

score 6 · Accepted Answer · answered Feb 26 '19 at 15:42

6

The backslash is just part of the syntax of a block.

\ -> { is equivalent to Java's () -> { - a lambda taking no parameters.

\ k -> { is equivalent to Java's k -> { - a lambda taking one parameter whose type is inferred.

answered Feb 26 '19 at 15:42

Michael

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Lol, you and I were working to close this out at the same time. Thanks for your help. – Jonathan M Feb 26 '19 at 15:43

score 3 · Answer 2 · answered Feb 26 '19 at 15:42

3

This question was originally posted when thinking the code was Java. Upon discovering it is Gosu, the answer is given by the docs.

Lambdas in Gosu are set off by the backslash.

answered Feb 26 '19 at 15:42

Jonathan M

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What do the backslashes do in this Gosu code?

2 Answers2