[racket] representing delta blue's relations in typed racket

On 01/11/2015 03:52 PM, Anthony Carrico wrote:
> On possibility is to avoid putting values into Variables at all, and to
> just keep blue delta bookkeeping and thunks in the structures. I think
> this would avoid the trouble, but I still wonder if the original version
> is somehow possible.

That turned out to be a good idea :). It is pretty lightly tested, but
my code seems to be working. Here is an example transcript:

x=0 y=1 z=2          ; printf of 3 TR variables
add medium x + y = z ; here is my first constaint
x=1 y=1 z=2          ; blue delta has set! x
add weak x = 10      ; add another constraint
x=10 y=-8 z=2 ;      ; blue delta has set! x and y
add strong y = 20    ; add another constraint
x=10 y=20 z=30       ; blue delta has set! y and z
add strong x + y = 20 ; add another constraint
x=-10 y=20 z=10      ; can't honor weak x = 10
remove strong constraint y=20
x=10 y=0 z=10        ; now weak x = 10 is honored.

Nice.

-- 
Anthony Carrico


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