core.checkedint added to druntime

[bearophile via Digitalmars-d-announce]

Walter Bright:

> Because there is no ubyte/byte/short/ushort math in C, C++ or 
> D. There is only int/long math.

A little of ubyte math is present, perhaps for this you add 
"uinc", "sinc", "udec", "sdec" functions to core.checkedint that 
support ubyte/byte/short/ushort types too:

void main() {
     ubyte x = 100;
     x++;
}


But you are right, in D if you sum two ubytes you get an int:

void main() {
     ubyte x = 100;
     ubyte y = 200;
     pragma(msg, typeof(x + y)); // Prints "int"
}


Yet sometimes you want to perform safe math operations on 
ubytes/bytes/shorts/ushorts, and keep the same type for the 
results. So I presume a future Phobos Safe math based on 
core.checkedint will need to check the ranges by itself, to allow 
checked assignments back to the same types:

void main() {
     Safe!ubyte x = 100;
     Safe!ubyte y = 200;
     Safe!ubyte z = x + y;
}

Bye,
bearophile