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Add annotation to specify operators precedence. #69
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This would be a lifesaver for writing code and a potential anchor for reading it. If you attach the lifesaver to the anchor, does it sink or float? I think it floats in general but maybe not in scala. |
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+1 would be extremely useful. @paulp I don't think the use of a static table (as it is now) makes the code more readable. AFAIK, most people don't know what is the current operators precedence. |
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To resurrect this issue, please rework it as an issue/PR against Lightbend Scala (ie. scala/scala). |
soronpo
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to soronpo/scala.github.com
that referenced
this issue
Feb 9, 2017
- Removed author's notes, and Adding them here: 1. Unary types are not crucial as infix type precedence, but good for completeness. 2. For the proposal section, I can copy-paste the specifications from expression and modify them to types, if it so required. 3. Would love some help to complete what happens in different programming languages. 4. I think it is very unlikely that variance annotation will interact with literal types, so the confusion is not that critical. 5. Backward compatibility: I don't know if providing a flag to select the precedence is good or not. IMHO, it is better to create a tool that adds brackets to convert code to the old associativity. @jvican's suggestion to use a tool to analyze libraries and check if they are compatible or not is interesting. Don't know if I have time to make it. It is more useful for me to explore the scala compiler code, and make a PR for this SIP 😄 - Modified the example to `/` instead of `*` because currently dotty has bug and does not allow `*` infix type. - Removed scala meta section. - Removed extended proposal alternative: It is possible to extend this proposal and allow the developer to annotate the expected associativity and precedence per operation. I personally don't like this, but if such a solution is better for the community, then I will gladly modify this SIP to reflect that. See the following [Typelevel Scala issue](typelevel/scala#69) for the suggestion.
milessabin
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that referenced
this issue
Jul 31, 2017
Non local returns aren't eliminated after inlined in 2.11 or 2.12
```
⚡ scala
Welcome to Scala 2.12.1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.
scala> @inlune def foo(a: => Any) = if ("".isEmpty) a else ""
<console>:11: error: not found: type inlune
@inlune def foo(a: => Any) = if ("".isEmpty) a else ""
^
scala> @inline def foo(a: => Any) = if ("".isEmpty) a else ""
foo: (a: => Any)Any
scala> class InlineReturn { def test: Any = foo(return "") }
defined class InlineReturn
scala> :javap -c InlineReturn#test
public java.lang.Object test();
Code:
0: new #4 // class java/lang/Object
3: dup
4: invokespecial #32 // Method java/lang/Object."<init>":()V
7: astore_1
8: getstatic #36 // Field $line4/$read$$iw$$iw$.MODULE$:L$line4/$read$$iw$$iw$;
11: aload_1
12: invokedynamic #59, 0 // InvokeDynamic #0:apply:(Ljava/lang/Object;)Lscala/Function0;
17: invokevirtual #63 // Method $line4/$read$$iw$$iw$.foo:(Lscala/Function0;)Ljava/lang/Object;
20: goto 44
23: astore_2
24: aload_2
25: invokevirtual #66 // Method scala/runtime/NonLocalReturnControl.key:()Ljava/lang/Object;
28: aload_1
29: if_acmpne 39
32: aload_2
33: invokevirtual #69 // Method scala/runtime/NonLocalReturnControl.value:()Ljava/lang/Object;
36: goto 41
39: aload_2
40: athrow
41: goto 44
44: areturn
Exception table:
from to target type
8 20 23 Class scala/runtime/NonLocalReturnControl
```
```
⚡ ~/scala/2.11.8/bin/scala
Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.
scala> @inline def foo(a: => Any) = if ("".isEmpty) a else ""
foo: (a: => Any)Any
scala> class InlineReturn { def test: Any = foo(return "") }
defined class InlineReturn
scala> :javap -c InlineReturn#test
public java.lang.Object test();
Code:
0: new #4 // class java/lang/Object
3: dup
4: invokespecial #13 // Method java/lang/Object."<init>":()V
7: astore_1
8: getstatic #19 // Field .MODULE$:L;
11: new #21 // class InlineReturn$$anonfun$test$1
14: dup
15: aload_0
16: aload_1
17: invokespecial #24 // Method InlineReturn$$anonfun$test$1."<init>":(LInlineReturn;Ljava/lang/Object;)V
20: invokevirtual #28 // Method .foo:(Lscala/Function0;)Ljava/lang/Object;
23: goto 39
26: astore_2
27: aload_2
28: invokevirtual #31 // Method scala/runtime/NonLocalReturnControl.key:()Ljava/lang/Object;
31: aload_1
32: if_acmpne 40
35: aload_2
36: invokevirtual #34 // Method scala/runtime/NonLocalReturnControl.value:()Ljava/lang/Object;
39: areturn
40: aload_2
41: athrow
Exception table:
from to target type
8 26 26 Class scala/runtime/NonLocalReturnControl
scala> :quit
```
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Is it possible to add some kind of annotation to control the precedence of functions with symbolic names, something similar to what Haskell has?
So the code like this:
"string" -> "value" -> 10, would be parsed as("string" -> ("value" -> 10)).The text was updated successfully, but these errors were encountered: