On Thursday, 19 January 2017 at 02:00:10 UTC, Ali Çehreli wrote:
On 01/18/2017 05:22 PM, Yuxuan Shui wrote:
Somehow I can't use ubyte variables behind 'case', but ulong
works fine.
Why is that?
case expressions must be constants:
"The case expressions must all evaluate to a constant value or
array, or a runtime initialized const or immutable variable
of
integral type."
https://dlang.org/spec/statement.html#SwitchStatement
The fact that it compiles for ulong looks like a bug to me. It
compiles probably because switch is most likely implemented in
terms of a chained if-else-if statements by the compiler and it
just works because there is no explicit check whether they are
constant or not.
Ali
If you try:
void main() {
alias TestType = ulong; // won't compile if = ubyte
import std.stdio;
TestType a,b,c;
readf("%s %s %s ", &a, &b, &c);
final switch(c){
case a: writeln("a");break;
case b: writeln("b");break;
default: assert(false);
}
}
Then the error message:
test.d(7): Error: case variables not allowed in final switch
statements
test.d(8): Error: case variables not allowed in final switch
statements
Makes it looks like that "case variable" is an intended feature.
