Well, I typed this out from memory so there's an error, of course. `(tmp & 1)` should be `(input & 1)`.
On Fri, Nov 11, 2022 at 8:31 AM David Lloyd <david.ll...@redhat.com> wrote: > I encountered this issue as well; for now I'm using the following > transformation: > > long tmp = input >>> 1; > double output = ((double) tmp) * 2.0 + (tmp & 1); > > I... *think* it's correct but I'm not 100% sure and have a long-standing > TODO to try and figure it out... > > On Sat, Nov 5, 2022 at 7:17 PM Johannes Kuhn <i...@j-kuhn.de> wrote: > >> When I tried to implement an WASM transpiler, I noticed some missing >> conversion methods from unsigned types to floating point, for example >> from unsigned long to a double. >> >> For the meaning of unsigned long, see Long.toUnsignedString(long i). >> >> Converting between unsigned long and floating point is not a trivial >> task, as it probably requires some bit manipulation. >> >> In particular, I would love to see the following methods added*: >> >> - double Double.fromUnsignedLong(long i) >> - long Double.toUnsignedLong(double d) >> - float Float.fromUnsignedLong(long i) >> - long Float.toUnsignedLong(float f) >> >> * Subject to bikeshedding - I don't care about the name, or if it is >> added to the Long class. >> >> Currently, I don't think that additional methods for unsigned int are >> necessary - as it is possible to cast between long and int, but feel >> free to correct me. >> >> In WASM, the specification for those methods can be found here: >> >> https://www.w3.org/TR/wasm-core-1/#op-trunc-u >> https://www.w3.org/TR/wasm-core-1/#op-convert-u >> >> Note that the WASM specification is undefined for some values, notably >> NaN, infinities, and values that fall out of the range. >> >> As *I* want to use it to implement WASM instructions, I do not have any >> strong opinion on the undefined cases - for example, returning the >> nearest unsigned long value or throwing an exception is fine for me. >> >> What do you think? >> >> - Johannes >> >> > > -- > - DML • he/him > -- - DML • he/him
