functionality that should probably exist in Racket's libraries
| file | purpose |
|---|---|
| circular.rkt | ovide create-circular-list-stream) |
| hash-contract.rkt | ovide |
| hexagon.rkt | hexagons as images |
| list.rkt | ovide |
| pict-hexagon.rkt | hexagons in pict format, derived from image format |
| struct-accessor.rkt | ovide |
| suspension.rkt | ovide |
| toint.rkt | ovide toint) |
| xsend.rkt | a library that protects calls from exceptions and overly slow clients |