Table of Dynamic type issues all in one place

[Ilir-Liburn]

Can't find a way to style table here, so coloured version is here
http://guideto.rf.gd/dynamic.html

TARGET	VALUE	== TRUE	== FALSE	IF (VALUE )	CAST:BOOL	! = 0	== 0
Flash	null	false	false	false	false	true	false
HL	null	false	false	false	false	false	true
Java	null	false	false	false	false	true	false
C#	null	false	false	false	false	true	false
CPP	null	false	false	false	false	true	false
Node/JS	null	false	false	false	null	true	false
Python	null	false	false	false	null	true	false
Lua	null	false	false	false	null	true	false
Neko	null	false	false	false	null	true	false
TARGET	VALUE	== TRUE	== FALSE	IF (VALUE )	CAST:BOOL	! = 0	== 0
Flash	instance	false	false	true	true	true	false
HL	instance	false	false	exception	exception	exception	exception
Java	instance	false	false	exception	exception	true	false
C#	instance	false	false	exception	exception	true	false
CPP	instance	false	true	false	false	false	true
Node/JS	instance	false	false	true	instance	true	false
Python	instance	false	false	true	instance	true	false
Lua	instance	false	false	true	instance	true	false
Neko	instance	false	false	false	instance	true	false
TARGET	VALUE	== TRUE	== FALSE	IF (VALUE )	CAST:BOOL	! = 0	== 0
Flash	0	false	true	false	false	false	true
HL	0	false	false	false	false	false	true
Java	0	false	false	exception	exception	false	true
C#	0	false	true	exception	exception	false	true
CPP	0	false	true	false	false	false	true
Node/JS	0	false	true	false	0	false	true
Python	0	false	true	false	0	false	true
Lua	0	false	false	true	0	false	true
Neko	0	false	false	false	0	false	true
TARGET	VALUE	== TRUE	== FALSE	IF (VALUE )	CAST:BOOL	! = 0	== 0
Flash	1	true	false	true	true	true	false
HL	1	false	false	true	true	true	false
Java	1	false	false	exception	exception	true	false
C#	1	true	false	exception	exception	true	false
CPP	1	true	false	true	true	true	false
Node/JS	1	true	false	true	1	true	false
Python	1	true	false	true	1	true	false
Lua	1	false	false	true	1	true	false
Neko	1	false	false	false	1	true	false

[RedHairHead]

Are these exceptions thrown at compile time or run time?

[Ilir-Liburn]

Runtime of course. For example (HL); Uncaught exception: Can't cast #Some to f64

Notice how Flash is only target which is passing test. Haxe orginated from Flash. I can do workarounds here, but I'm afraid Neko and HL are out of my range (I think).

Haxe is cross-platform, so it should handle dynamic type correctly across the targets. And that could bring one more cool thing; notice how value == true is a true only for numeric values! So you could build safe abstract type like this:

abstract Safe(Dynamic) {
    @:from public static inline function fromObject(v:Dynamic) { return cast v; }
    @:to public inline function toBool():Bool return this != null && this != 0;
    @:to public inline function toNumber():EitherType<Int, Float> return this == true ? cast this : 0;
    @:to public inline function toInstance<T>():T return cast this; 
}

[Aurel300]

Thank you for the clear table.

I think there are some issues, however. You base the "correct" result on what Flash behaviour is like. Please keep in mind that Flash/AS3.0 is a dynamically-typed language and so will not complain too much about type problems.

For example, I would argue that if (value) should always throw an exception if value is not a Bool, i.e. the way Java does it. Similarly, why should true == 1? Etc.

[Simn]

Most of this has to remain undefined behavior for performance reasons. We have to rely on the native behavior of the target here.

[Ilir-Liburn]

Flash is a mixture of static and dynamic. Note how dynamic targets (like Node/JS, Python) behave natively correct (two more passing test) except LUA and Neko (HL). C# is failing only on if() and cast (Java on ==true in addition), which can be easily fixed.

@Aurel300 , if (value) is standard test if value holds instance (not null), if number is not zero or bool is a true

[Aurel300]

@Ilir-Liburn if (value) is a standard test for that on different platforms, for different reasons (in C/C++ because pointers happen to be numbers, in dynamic languages because why not). It is not a standard test in Haxe, unless using Dynamic.

[Ilir-Liburn]

@Aurel300, exactly. This is a Dynamic test

[Ilir-Liburn]

Above link updated, added if(!value) column and added Boolean values tests

[Ilir-Liburn]

Revisited for rc.3, added PHP test and -1 value test

[jdonaldson]

my 2 cents: the table should be a documentation feature, the variance here is not a bug.

[Aurel300]

@jdonaldson +1; Simn told me this is why the issue remains open (with the documentation label).