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digitalmars.D.learn - is expression with static if matches wrong type

reply "tcak" <tcak gmail.com> writes:
[code]
import std.stdio;

public void setMarker(M)( size_t markerIndex, M markerValue )
	if(
		is(M: ulong) || is(M: long) ||
		is(M: uint) || is(M: int) ||
		is(M: ushort) || is(M: short) ||
		is(M: ubyte) || is(M: byte) || is(M: char) || is(bool) ||
		is(M: double) ||
		is(M: float)
	)
{
	static if( is(M: ulong) || is(M: long) ){
		std.stdio.writeln("Here 1: ", typeid(M));
	}

	else static if( is(M: uint) || is(M: int) ){
		std.stdio.writeln("Here 2: ", typeid(M));
	}

	else static if( is(M: ushort) || is(M: short) ){
		std.stdio.writeln("Here 3: ", typeid(M));
	}

	else static if( is(M: ubyte) || is(M: byte) || is(M: char) || 
is(bool) ){
		std.stdio.writeln("Here 4: ", typeid(M));
	}
}

void main() {
	setMarker( 0, cast(ubyte)5 );
}

[/code]



Result:
Here 1: ubyte


Compiler and OS:
DMD 2.067.1  on Ubuntu 14.04 64-bit


Expected:
Here 4: ubyte


is(my expectation) wrong?
May 22 2015
parent reply "tcak" <tcak gmail.com> writes:
On Saturday, 23 May 2015 at 04:35:55 UTC, tcak wrote:

 [code]
 import std.stdio;

 public void setMarker(M)( size_t markerIndex, M markerValue )
 	if(
 		is(M: ulong) || is(M: long) ||
 		is(M: uint) || is(M: int) ||
 		is(M: ushort) || is(M: short) ||
 		is(M: ubyte) || is(M: byte) || is(M: char) || is(bool) ||
 		is(M: double) ||
 		is(M: float)
 	)
 {
 	static if( is(M: ulong) || is(M: long) ){
 		std.stdio.writeln("Here 1: ", typeid(M));
 	}

 	else static if( is(M: uint) || is(M: int) ){
 		std.stdio.writeln("Here 2: ", typeid(M));
 	}

 	else static if( is(M: ushort) || is(M: short) ){
 		std.stdio.writeln("Here 3: ", typeid(M));
 	}

 	else static if( is(M: ubyte) || is(M: byte) || is(M: char) || 
 is(bool) ){
 		std.stdio.writeln("Here 4: ", typeid(M));
 	}
 }

 void main() {
 	setMarker( 0, cast(ubyte)5 );
 }

 [/code]



 Result:
 Here 1: ubyte


 Compiler and OS:
 DMD 2.067.1  on Ubuntu 14.04 64-bit


 Expected:
 Here 4: ubyte


 is(my expectation) wrong?


I have found my mistake. is(M: type) matches if M can be 
converted to type automatically. Thus, it matches to ulong. I 
changed it to is(M == type) and it works correctly now.
May 22 2015
parent reply "ZombineDev" <valid_email he.re> writes:
On Saturday, 23 May 2015 at 04:40:28 UTC, tcak wrote:

 [snip]


Yup, you need to use == to match the exact type.
Btw, you can use enum templates from std.traits, to accomplish 
the same with less code:

public void setMarker(M)( size_t markerIndex, M markerValue )
	if(isScalarType!M)
{
     //...
}

http://dlang.org/phobos/std_traits.html#isScalarType
May 24 2015
parent "ZombineDev" <valid_email he.re> writes:
On Sunday, 24 May 2015 at 14:46:52 UTC, ZombineDev wrote:

 [snip]


Correction: not exactly the same, because isScalar also allows 
wchar, dchar and const and immutable versions of those 'scalar' 
types.
May 24 2015