Do not the Kernel arguments support the class 'bool'?

[17150934]

When I set the type-hinted of my Kernel arguments as 'bool', there existed an error: TaichiSyntaxError: Invalid type annotation (argument 0) of Taichi kernel: <class 'bool'> So, do not the Kernel arguments support the class 'bool'?

[AD1024]

Thanks for the issue. Currently bool type is not (explicitly) one of the primitive types in Taichi. There is a u1 type, which is used as bool. A workaround is to use int (or other integer types) to mimic its behavior.

@strongoier I noticed that the u1 type is defined in C++ but not exposed to the Python frontend (used in export_lang.cpp but not referenced in primitive_types.py). Should we use it when encountering the bool type during compilation?

[strongoier]

u1 type has not been fully supported yet (https://github.com/taichi-dev/taichi/issues/577), and we plan to support it in the future. For now we need to use int as a workaround.

[re-xyr]

As a first step towards adding the proper bool type, we're going to add bool as an alias of i32.

Specifically:

• x: bool is equivalent to x: i32
• -> bool is equivalent to -> i32
• bool(x) is equivalent to ti.cast(x, i32).

This is only a temporary workaround as we work on a more permanent solution.