## Saturday, July 21, 2012

### Grid dimensions

The dimensions of a grid are mutable, but the area of the grid is not. As such, in my computer algebra system the dimensions relation is implemented as a place:
(setf [dimensions [[1 2 3] [4 5 6]]] [3 2])

The transpose operation on matrices can be implemented as an automorphism that rearranges the elements of the collection and that reverses the dimensions of the grid.
(zap reverse [dimensions coll])

Any permutation operation, including reverse, can be applied to the dimensions place without every producing an error because permutations do not change the area part of the underlying grid structure.

## Sunday, July 1, 2012

### Reversible functional programming

In the current reversible functional programming framework implementation, all functions will have a set of places that that they effect in their argument. Functions that do not effect the :trash place are bijections. By default all functions trash their entire input and return their output, and they effect the top level place.

In our reversible FP framework, our interest is to deviate from the default setup by establishing bijections and zap functions whenever possible. Parallelism occurs when functions that effect separate places are composed together.