On Thu, Dec 11, 2008 at 11:10 AM, François Perrad <[EMAIL PROTECTED]> wrote: > 2008/12/11 Will Coleda via RT <[EMAIL PROTECTED]>: >> On Thu Dec 11 01:51:23 2008, fperrad wrote: >>> The new opcode 'box' is limited by its 3 signatures that target Float, >>> Integer & String. >>> I propose the 3 following new opcodes : >> >>> - true >>> - false >> >> These can be approximated with: >> >> $P0 = box 1 >> $P0 = box 0 > > No. > > On Lua, LuaNumber maps Float & Integer, LuaBoolean maps Boolean. > So, with the current signature of box : > $P0 = box 1 > is equivalent to > $P0 = new 'LuaNumber' > set $P0, 1 > but I want a LuaBoolean, because I want respect the precise rules of > coercion for arithmetic operations. > The expected behavior with a LuaNumber containing 1 and with a > LuaBoolean containing 1 is not same. > > On WMLScript, WmlsInteger maps Integer, WmlsBoolean maps Boolean > So, > $P0 = box 1 > is equivalent to > $P0 = new 'WmlsInteger' > set $P0, 1 > but I want a WmlsBoolean. > > >> >> I know you'll end up with an Integer (or, perhaps, a LuaInt) instead of >> a Boolean here. That doesn't work? >> >>> - undef or nil (less Perlish) >> >> undef and null are two different things in parrot, but we do have an >> opcode for one of them, at least: >> >> $P0 = null >> >>> After some experiments with bytecode translation, >>> in WMLScript (r33655) and in Lua (r33760), >>> it seems obvious that we need them. >> >> Can you explain why? >> > > With the opcode 'box', I could rewrite the generation of : > - ConstantInteger > - ConstantFloat > - ConstantString > but not : > - ConstantBoolean > - ConstantNil > > That's seems not homogene. > >>> François.
As I understand it, box is designed to deal /only/ with promoting the 3 basic register types (SIN) to PMCs of the appropriate HLL type (just like autoboxing in PCC), not to provide a way to promote literal values for arbitrary core PMCs. So the discontinuity is that not every core PMC has a corresponding register type. I think a more general approach might be to have an opcode that combined 'new' and 'assign'. You could even have it respect the HLL mappings if present. $P1 = new_init 'LuaBoolean', 1 # explicitly pick a type. $P3 = new_init 'String, 'good luck' # this type is overridden by the HLL, get a LuaString as a result. But ISTR this was shot down by Chip some time ago, and what little support there is for it (new_from_string) is slated to be removed. (IAN The Architect) -- Will "Coke" Coleda
