Finally, that little e. is cleaned up. convert_name was a bit of a pain
(in that it relied on modifying the expression rather than returning a
new one, or more that such behavior was relied on).
Sum expressions pull the negation through extend expressions allowing
them to switch to subtraction when appropriate, and offset_cast reaches
past negation to check for extend expressions. This has eliminated all
negation-only instructions from the motor-point, shaving off more
instructions (now 27 not including the return).
I don't know why I didn't think to do it this way before, but simply
recursing into each operand for + or - expressions makes it much easier
to generate correct code. Fixes the motor-point test.
This removes all the special cases and thus it should be more robust. It
did show up some out-by-one (or a factor of two!) errors elsewhere in
the group mask calculations.
This makes working with the plethora of types a little easier still. The
check for an algebra expression in field_expr needed to be moved up
because the struct code thought the algebra type was a normal vector.
And vis-versa.
I'm not sure what I was thinking, but I've decided that not being able
to cast the pseudo-scalar from float to double (for printf etc) was a
bug.
Failing to promote ints to the algebra type results in a segfault in
assignment of a multi-vector due to the symbol pointer walking off the
end of the list of symbols.
And convert addition to subtraction when extend expressions are not
involved. This has taken my little test down to 56 instructions total
(21 for `l p ~l`), down from 74 (39).
This takes care of chained sums of extend expressions. Now `l p ~l` has
only four extend instructions which is expected for the code not
detecting the cross product that always produces 0.
This goes a ways towards minimizing extend expressions, even finding
zeros and thus eliminating whole branches of expressions, but shows the
need for better handling of chained sums of extends.
Any geometric algebra product of two negatives cancels out the negative,
and if the result is negative (because only one operand was negative),
the negation is migrated to above the operation. This resulted in
removing 2 instructions from one if my mini-tests (went from 74 to 78
with the addition/subtraction change, but this takes it back to 76
instructions).
Summed extend expressions are used for merging a sub-vector with a
scalar. Putting the vector first in the sum will simplify checks later
on (it really doesn't matter which is first so long as it's consistent).
Subtraction is implemented as adding a negative (with the plan of
optimizing it later). The idea is to give tree inspection and
manipulation a more consistent view without having to worry about
addition vs subtraction.
Negation is moved as high as possible in the expression, but is always
below an extend expression. The plane here is that the manipulation code
can bypass an alias-add-extend combo and see the negation.
Simple k-vectors don't use structs for their layout since they're just
an array of scalars, but having the structs for group sets or full
multi-vectors makes the system alignment agnostic.
It's implemented as the Hodge dual, which is probably reasonable until
people complain. Both ⋆ and ! are supported, though the former is a
little hard to see in Consola.
That was surprisingly harder than expected due to recursion and a
not-so-good implementation in expr_negate (it went too high-level thus
resulting in multivec expressions getting to the code generator).
But only for scalar divisors. The simple method of AB†/(BB†) works only
if B is a versor and there's also the problem of left and right
division. Thanks to sudgy for making me stop and think before I actually
implemented anything (though he mentioned only that it doesn't work for
general mutli-vector divisors).
That was tedious. I can't say I'm looking forward to writing the tests
for 3d. And even though trivector . bivector and bivector . trivector
give the same answer, they're not really commutative when it comes to
the code.
I didn't particularly like that solution due to the implied extra
bandwidth (probably should profile such sometime), but I think the
extend operations could be merged into simple assignments by the
optimizer at some stage (or further cleaned up when this stuff gets
moved to actual code gen where it should be).
Also, correct the handling of scalars in dot and wedge products: it
turns out s.v and s^v both scale. However, it seems the CSE code loses
things sometimes.
This has shown the need for more instructions, such as a 2d wedge
product and narrower swizzles. Also, making dot product produce a vector
instead of a scalar was a big mistake (works nicely in C, but not so
well in Ruamoko).
