Go has a strict type separation between int and bool. For a normal usage this is OK. I guess it also ease assembly portability because there is not always a machine instruction to do so.
For bit hacking, this is an unfortunate limitation. A handy feature of bool <-> int conversion is that true is converted to 1 and any integer different of zero to true. As a consequence, when we write int(bool(x)) we get 0 when x is 0, and 1 when x is not 0. I checked the math/bits package and there is not an equivalent function. Is there a way around this that avoids the conditional branching ? The use case I have to test if an integer is in a quite small constant set of integers. With bool <-> int conversion, we can use binary operation like this for instance which would be valid in C r := int(bool(v^v1))&int(bool(v^v2))&int(bool(v^v3)) This is to be compared with r := v==v1 || v==v2 || v==v3 The second form is of course more readable, but will also have a conditional branch at each ||. If most tested integers are different from v1, v2 and v3, the first form seam to me more efficient due to pipelining. Though branching prediction can mitigate the penalty. The best I could do as valid Go alternative is this r := (v^v1)*(v^v2)*(v^v3) but the multiplication is obviously not efficient. Did I miss something ? -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/a2b743d7-011d-481f-9a0f-3f00f4507328n%40googlegroups.com.
