Binary literals #23
Comments
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What type would it become? Int? Short? Byte? Long? String? |
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You would want to have some prefix signify the meaning of the subsequent 1s and 0s, and a suffix signify the type, consistent with hex. e.g. |
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I think it could work very similarly to hex literals ( For example: 0b111Z // Byte
0b111S // Short
0b111 // Int
0b111L // LongWhat do you all think? EDIT: I think this is almost exactly what @propensive is proposing. |
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It's exactly the same, except I was scared of the possible ambiguity of |
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@non's proposal is also coherent with Java 8's binary literals. |
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The To counteract that, add
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Valid point. @propensive wrote:
For instance, this would be inconsistent:
However, I realize I had missed some jokes in your message and I'm unsure about others. |
These methods are "signature polymorphic", which means that compiler
should not:
1. adapt the arguments to `Object`
2. wrap the repeated parameters in an array
3. adapt the result type to `Object`, but instead treat it as it
it already conforms to the expected type.
Dispiritingly, my initial attempt to implement this touched the type
checker, uncurry, erasure, and the backend.
However, I realized we could centralize handling of this in the typer
if at each application we substituted the signature polymorphic
symbol with a clone that carried its implied signature, which is
derived from the types of the arguments (typechecked without an
expected type) and position within and enclosing cast or block.
The test case requires Java 7+ to compile so is currently embedded
in a conditionally compiled block of code in a run test.
We ought to create a partest category for modern JVMs so we can
write such tests in a more natural style.
Here's how this looks in bytecode. Note the `bipush` / `istore`
before/after the invocation of `invokeExact`, and the descriptor
`(LO$;I)I`.
```
% cat sandbox/poly-sig.scala && qscala Test && echo ':javap Test$#main' | qscala
import java.lang.invoke._
object O {
def bar(x: Int): Int = -x
}
object Test {
def main(args: Array[String]): Unit = {
def lookup(name: String, params: Array[Class[_]], ret: Class[_]) = {
val lookup = java.lang.invoke.MethodHandles.lookup
val mt = MethodType.methodType(ret, params)
lookup.findVirtual(O.getClass, name, mt)
}
def lookupBar = lookup("bar", Array(classOf[Int]), classOf[Int])
val barResult: Int = lookupBar.invokeExact(O, 42)
()
}
}
scala> :javap Test$#main
public void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
flags: ACC_PUBLIC
Code:
stack=3, locals=3, args_size=2
0: aload_0
1: invokespecial typelevel#18 // Method lookupBar$1:()Ljava/lang/invoke/MethodHandle;
4: getstatic typelevel#23 // Field O$.MODULE$:LO$;
7: bipush 42
9: invokevirtual typelevel#29 // Method java/lang/invoke/MethodHandle.invokeExact:(LO$;I)I
12: istore_2
13: return
LocalVariableTable:
Start Length Slot Name Signature
0 14 0 this LTest$;
0 14 1 args [Ljava/lang/String;
13 0 2 barResult I
LineNumberTable:
line 16: 0
}
```
I've run this test across our active JVMs:
```
% for v in 1.6 1.7 1.8; do java_use $v; pt --terse test/files/run/t7965.scala || break; done
java version "1.6.0_65"
Java(TM) SE Runtime Environment (build 1.6.0_65-b14-466.1-11M4716)
Java HotSpot(TM) 64-Bit Server VM (build 20.65-b04-466.1, mixed mode)
Selected 1 tests drawn from specified tests
.
1/1 passed (elapsed time: 00:00:02)
Test Run PASSED
java version "1.7.0_71"
Java(TM) SE Runtime Environment (build 1.7.0_71-b14)
Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode)
Selected 1 tests drawn from specified tests
.
1/1 passed (elapsed time: 00:00:07)
Test Run PASSED
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)
Selected 1 tests drawn from specified tests
.
1/1 passed (elapsed time: 00:00:05)
Test Run PASSED
```
This corrects an error in the change to the trait encoding in scala#5003: getters in traits should have empty bodies and be emitted as abstract. ``` % ~/scala/2.12.0-M4/bin/scalac sandbox/test.scala && javap -c T Compiled from "test.scala" public interface T { public abstract void T$_setter_$x_$eq(int); public int x(); Code: 0: aload_0 1: invokeinterface #15, 1 // InterfaceMethod x:()I 6: ireturn public int y(); Code: 0: aload_0 1: invokeinterface #20, 1 // InterfaceMethod y:()I 6: ireturn public void y_$eq(int); Code: 0: aload_0 1: iload_1 2: invokeinterface #24, 2 // InterfaceMethod y_$eq:(I)V 7: return public void $init$(); Code: 0: aload_0 1: bipush 42 3: invokeinterface #29, 2 // InterfaceMethod T$_setter_$x_$eq:(I)V 8: aload_0 9: bipush 24 11: invokeinterface #24, 2 // InterfaceMethod y_$eq:(I)V 16: return } % qscalac sandbox/test.scala && javap -c T Compiled from "test.scala" public interface T { public abstract void T$_setter_$x_$eq(int); public abstract int x(); public abstract int y(); public abstract void y_$eq(int); public static void $init$(T); Code: 0: aload_0 1: bipush 42 3: invokeinterface #21, 2 // InterfaceMethod T$_setter_$x_$eq:(I)V 8: aload_0 9: bipush 24 11: invokeinterface #23, 2 // InterfaceMethod y_$eq:(I)V 16: return public void $init$(); Code: 0: aload_0 1: invokestatic #27 // Method $init$:(LT;)V 4: return } ```
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To resurrect this issue, please rework it as an issue/PR against Lightbend Scala (ie. scala/scala). |
It would be nice if this scalac fork had built-in non-macro binary literals, similar to the macro-based one found in retronym's macrocosm
E.g. https://github.com/retronym/macrocosm/blob/master/src/main/scala/com/github/retronym/macrocosm/Macrocosm.scala#L72
Example:
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