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digitalmars.D - Proposal: Support for objects in switch statements

reply solidstate1991 <laszloszeremi outlook.com> writes:
After I started to alter my graphics engine to use the multiple 
kinds of bitmaps (now using multiple language features, like 
templates and aliases) on one layer, I noticed that type 
detection of bitmap objects would be easier and better readable, 
if instead of:

if(bitmapObject.classinfo == typeof(Bitmap4Bit)){
...
}else if(bitmapObject.classinfo == typeof(Bitmap8Bit)){...

I could easily use this:

switch(bitmapObject.classinfo){
case typeof(Bitmap4Bit):
...
case typeof(Bitmap8Bit):
}

On the other hand I cannot really think other uses for such 
language feature, maybe with structs.
Oct 31
next sibling parent Yuxuan Shui <yshuiv7 gmail.com> writes:
On Wednesday, 1 November 2017 at 01:16:32 UTC, solidstate1991 
wrote:
 After I started to alter my graphics engine to use the multiple 
 kinds of bitmaps (now using multiple language features, like 
 templates and aliases) on one layer, I noticed that type 
 detection of bitmap objects would be easier and better 
 readable, if instead of:

 if(bitmapObject.classinfo == typeof(Bitmap4Bit)){
 ...
 }else if(bitmapObject.classinfo == typeof(Bitmap8Bit)){...

 I could easily use this:

 switch(bitmapObject.classinfo){
 case typeof(Bitmap4Bit):
 ...
 case typeof(Bitmap8Bit):
 }

 On the other hand I cannot really think other uses for such 
 language feature, maybe with structs.
Maybe use something similar to recieve()? Like: match(obj, (Type1 x) => {}, (Type2 x) => {}, ...)
Oct 31
prev sibling next sibling parent angel <andrey.gelman gmail.com> writes:
On Wednesday, 1 November 2017 at 01:16:32 UTC, solidstate1991 
wrote:
 After I started to alter my graphics engine to use the multiple 
 kinds of bitmaps (now using multiple language features, like 
 templates and aliases) on one layer, I noticed that type 
 detection of bitmap objects would be easier and better 
 readable, if instead of:

 if(bitmapObject.classinfo == typeof(Bitmap4Bit)){
 ...
 }else if(bitmapObject.classinfo == typeof(Bitmap8Bit)){...

 I could easily use this:

 switch(bitmapObject.classinfo){
 case typeof(Bitmap4Bit):
 ...
 case typeof(Bitmap8Bit):
 }

 On the other hand I cannot really think other uses for such 
 language feature, maybe with structs.
The idea IS good, I am sure it has already happened to many. May it be there are some technical problems with it ?
Nov 04
prev sibling next sibling parent bauss <jj_1337 live.dk> writes:
On Wednesday, 1 November 2017 at 01:16:32 UTC, solidstate1991 
wrote:
 After I started to alter my graphics engine to use the multiple 
 kinds of bitmaps (now using multiple language features, like 
 templates and aliases) on one layer, I noticed that type 
 detection of bitmap objects would be easier and better 
 readable, if instead of:

 if(bitmapObject.classinfo == typeof(Bitmap4Bit)){
 ...
 }else if(bitmapObject.classinfo == typeof(Bitmap8Bit)){...

 I could easily use this:

 switch(bitmapObject.classinfo){
 case typeof(Bitmap4Bit):
 ...
 case typeof(Bitmap8Bit):
 }

 On the other hand I cannot really think other uses for such 
 language feature, maybe with structs.
While it's not entirely ideal something like this works. ``` template ClassName(T, string mod = __MODULE__) { enum ClassName = mod ~ "." ~ T.stringof; } property string className(T)(T o) { return o.classinfo.toString(); } ``` Example: ``` final switch (bitmapObject.className) { case ClassName!Bitmap4Bit: ... break; case ClassName!Bitmap8Bit: ... break; } ```
Nov 05
prev sibling parent Atila Neves <atila.neves gmail.com> writes:
On Wednesday, 1 November 2017 at 01:16:32 UTC, solidstate1991 
wrote:
 After I started to alter my graphics engine to use the multiple 
 kinds of bitmaps (now using multiple language features, like 
 templates and aliases) on one layer, I noticed that type 
 detection of bitmap objects would be easier and better 
 readable, if instead of:

 if(bitmapObject.classinfo == typeof(Bitmap4Bit)){
 ...
 }else if(bitmapObject.classinfo == typeof(Bitmap8Bit)){...

 I could easily use this:

 switch(bitmapObject.classinfo){
 case typeof(Bitmap4Bit):
 ...
 case typeof(Bitmap8Bit):
 }

 On the other hand I cannot really think other uses for such 
 language feature, maybe with structs.
Checking for types at runtime is a code smell in OOP. Sometimes necessary, especially if doing multiple dispatch, but never done gladly. There's already a way to dispatch on type: virtual functions. Atila
Nov 06