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
