* At least stubbed out all (or almost all) `math/matrix' exports; many
have complete documentation (e.g. types, predicates, accessors,
constructors, for loops, conversion, much of "Comparing Matrices")
* Moved `matrix-zero?' and fixed to use (matrix-error-norm) as its norm
* Added `matrix-basis-cos-angle' (currently a stub; should return smallest
singular value of a certain matrix multiplication)
* Gram-Schmidt using vector type
* QR decomposition
* Operator 1-norm and maximum norm; stub for 2-norm and angle between
subspaces (`matrix-basis-angle')
* `matrix-absolute-error' and `matrix-relative-error'; also predicates
based on them, such as `matrix-identity?'
* Lots of shuffling code about
* Types that can have contracts, and an exhaustive test to make sure
every value exported by `math/matrix' has a contract when used in
untyped code
* Some more tests (still needs some)
* Split "matrix-constructors.rkt" into three parts:
* "matrix-constructors.rkt"
* "matrix-conversion.rkt"
* "matrix-syntax.rkt"
* Made `matrix-map' automatically inline (it's dirt simple)
* Renamed a few things, changed some type signatures
* Fixed error in `matrix-dot' caught by testing (it was broadcasting)
* Rewrote matrix comprehensions in terms of array comprehensions
* Removed `in-column' and `in-row' (can use `in-array', `matrix-col' and
`matrix-row')
* Tons of new rackunit tests: only "matrix-2d.rkt" and
"matrix-operations.rkt" are left (though the latter is large)
* Finally added `array-axis-expand' as a dual for `array-axis-reduce'
in order to implement `vandermonde-matrix' elegantly
* Better, shorter matrix multiply; reworked all matrix arithmetic
* Split "matrix-operations.rkt" into at least 5 parts:
* "matrix-operations.rkt"
* "matrix-basic.rkt"
* "matrix-comprehension.rkt"
* "matrix-sequences.rkt"
* "matrix-column.rkt"
Added "matrix-constructors.rkt"
Added `matrix', `row-matrix', and `col-matrix' macros
A lot of other little changes
Currently, `in-row' and `in-column' are broken. I intend to implement
them in a way that makes them work in untyped and Typed Racket.
