Feature/inheritdoc and proper usecase comment inheritance/override #70
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added 5 commits
December 22, 2011 00:52
After all, not sure this is the best place to put it
|
I added you to the scala organization. I have to send this one back to the drawing board as well though.
I spot the whitespace errors with "git diff", which is easier than it sounds because I have it configured to show whitespace differences in reverse video. So introducing new whitespace looks like a giant white blanket attacking the nearby code. |
szeiger
pushed a commit
to szeiger/scala
that referenced
this pull request
Mar 20, 2018
Use delegation over inheritance
romanowski
pushed a commit
to romanowski/scala
that referenced
this pull request
Jun 13, 2018
Refchecks - another warnings cleanup
olafurpg
added a commit
to olafurpg/scala
that referenced
this pull request
Jul 17, 2018
This commit uncomments the disabled `productElementName` method.
The benefit of this change is that it becomes possible to pretty-print
`Product` instances with field, for example
```scala
case class User(name: String, age: Int)
def pretty(p: Product): String =
p.productElementNames.zip(p.productIterator)
.map { case (name, value) => s"$name=$value" }
.mkString(p.productPrefix + "(", ", ", ")")
toPrettyProduct(User("Susan", 42))
// res0: String = User(name=Susan, age=42)
```
The downside of this change is that it produces more bytecode for each
case-class definition. I am not versed enough in reading javap output
to determine the exact bytecode size for a given method. I tried the
following:
```scala
> case class A(a: Int, b: Int, c: Int)
> :javap -c A
public java.lang.String productElementName(int);
Code:
0: iload_1
1: istore_2
2: iload_2
3: tableswitch { // 0 to 2
0: 28
1: 33
2: 38
default: 43
}
28: ldc scala#78 // String a
30: goto 58
33: ldc scala#79 // String b
35: goto 58
38: ldc scala#80 // String c
40: goto 58
43: new scala#67 // class java/lang/IndexOutOfBoundsException
46: dup
47: iload_1
48: invokestatic scala#65 // Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
51: invokevirtual scala#70 // Method java/lang/Object.toString:()Ljava/lang/String;
54: invokespecial scala#73 // Method java/lang/IndexOutOfBoundsException."<init>":(Ljava/lang/String;)V
57: athrow
58: areturn
```
olafurpg
added a commit
to olafurpg/scala
that referenced
this pull request
Jul 17, 2018
This commit uncomments the disabled `productElementName` method.
The benefit of this change is that it becomes possible to pretty-print
`Product` instances with field, for example
```scala
case class User(name: String, age: Int)
def pretty(p: Product): String =
p.productElementNames.zip(p.productIterator)
.map { case (name, value) => s"$name=$value" }
.mkString(p.productPrefix + "(", ", ", ")")
toPrettyProduct(User("Susan", 42))
// res0: String = User(name=Susan, age=42)
```
The downside of this change is that it produces more bytecode for each
case-class definition. I am not versed enough in reading javap output
to determine the exact bytecode size for a given method. I tried the
following:
```scala
> case class A(a: Int, b: Int, c: Int)
> :javap -c A
public java.lang.String productElementName(int);
Code:
0: iload_1
1: istore_2
2: iload_2
3: tableswitch { // 0 to 2
0: 28
1: 33
2: 38
default: 43
}
28: ldc scala#78 // String a
30: goto 58
33: ldc scala#79 // String b
35: goto 58
38: ldc scala#80 // String c
40: goto 58
43: new scala#67 // class java/lang/IndexOutOfBoundsException
46: dup
47: iload_1
48: invokestatic scala#65 // Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
51: invokevirtual scala#70 // Method java/lang/Object.toString:()Ljava/lang/String;
54: invokespecial scala#73 // Method java/lang/IndexOutOfBoundsException."<init>":(Ljava/lang/String;)V
57: athrow
58: areturn
```
olafurpg
added a commit
to olafurpg/scala
that referenced
this pull request
Jul 18, 2018
This commit uncomments the disabled `productElementName` method.
The benefit of this change is that it becomes possible to pretty-print
`Product` instances with field, for example
```scala
case class User(name: String, age: Int)
def pretty(p: Product): String =
p.productElementNames.zip(p.productIterator)
.map { case (name, value) => s"$name=$value" }
.mkString(p.productPrefix + "(", ", ", ")")
toPrettyProduct(User("Susan", 42))
// res0: String = User(name=Susan, age=42)
```
The downside of this change is that it produces more bytecode for each
case-class definition. Running `:javacp -c` for a case class with three
fields yields the following results
```scala
> case class A(a: Int, b: Int, c: Int)
> :javap -c A
public java.lang.String productElementName(int);
Code:
0: iload_1
1: istore_2
2: iload_2
3: tableswitch { // 0 to 2
0: 28
1: 33
2: 38
default: 43
}
28: ldc scala#78 // String a
30: goto 58
33: ldc scala#79 // String b
35: goto 58
38: ldc scala#80 // String c
40: goto 58
43: new scala#67 // class java/lang/IndexOutOfBoundsException
46: dup
47: iload_1
48: invokestatic scala#65 // Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
51: invokevirtual scala#70 // Method java/lang/Object.toString:()Ljava/lang/String;
54: invokespecial scala#73 // Method java/lang/IndexOutOfBoundsException."<init>":(Ljava/lang/String;)V
57: athrow
58: areturn
```
Thanks to Adriaan's help, the estimated cost per `productElementName`
appears to be fixed 56 bytes and then 10 bytes for each field with
the following breakdown:
* 3 bytes for the
[string info](https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.3)
(the actual characters are already in the constant pool)
* 4 bytes for the tableswitch entry
* 2 bytes for the ldc to load the string
* 1 byte for areturn
In my opinion, the bytecode cost is acceptably low thanks to the fact
that field name literals are already available in the constant pool.
olafurpg
added a commit
to olafurpg/scala
that referenced
this pull request
Jul 18, 2018
This commit adds two methods to the `scala.Product` trait:
```scala
trait Product {
/** Returns the field name of element at index n */
def productElementName(n: Int): String
/** Returns field names of this product. Must have same length as productIterator */
def productElementNames: Iterator[String]
}
```
Both methods have a default implementation which returns the empty
string for all field names.
This commit then changes the code-generation for case classes to
synthesize a `productElementName` method with actual class field names.
The benefit of this change is that it becomes possible to pretty-print
case classes with field names, for example
```scala
case class User(name: String, age: Int)
def toPrettyString(p: Product): String =
p.productElementNames.zip(p.productIterator)
.map { case (name, value) => s"$name=$value" }
.mkString(p.productPrefix + "(", ", ", ")")
toPrettyString(User("Susan", 42))
// res0: String = User(name=Susan, age=42)
```
The downside of this change is that it produces more bytecode for each
case-class definition. Running `:javacp -c` for a case class with three
fields yields the following results
```scala
> case class A(a: Int, b: Int, c: Int)
> :javap -c A
public java.lang.String productElementName(int);
Code:
0: iload_1
1: istore_2
2: iload_2
3: tableswitch { // 0 to 2
0: 28
1: 33
2: 38
default: 43
}
28: ldc scala#78 // String a
30: goto 58
33: ldc scala#79 // String b
35: goto 58
38: ldc scala#80 // String c
40: goto 58
43: new scala#67 // class java/lang/IndexOutOfBoundsException
46: dup
47: iload_1
48: invokestatic scala#65 // Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
51: invokevirtual scala#70 // Method java/lang/Object.toString:()Ljava/lang/String;
54: invokespecial scala#73 // Method java/lang/IndexOutOfBoundsException."<init>":(Ljava/lang/String;)V
57: athrow
58: areturn
```
Thanks to Adriaan's help, the estimated cost per `productElementName`
appears to be fixed 56 bytes and then 10 bytes for each field with
the following breakdown:
* 3 bytes for the
[string info](https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.3)
(the actual characters are already in the constant pool)
* 4 bytes for the tableswitch entry
* 2 bytes for the ldc to load the string
* 1 byte for areturn
In my opinion, the bytecode cost is acceptably low thanks to the fact
that field name literals are already available in the constant pool.
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It didn't merge properly into master, because git was skipping one commit along the way (no idea why git was simply skipping over it). Rebased on the latest master and everything works fine now.
@paulp Do you use a tool to check for whitespace? If so, please let me know so I get a better pull request acceptance rate :p And btw, no, I can't see whether the pull request is not merging well, I'm not part of the scala organization :(