Notes of a technical nature
23. November 2016
A while back I wrote a parser for R6RS Scheme numbers, or the
string->number procedure. Numbers in Scheme are somewhat
sophisticated and can be written in some surprising variations and I
wanted some test inputs for verifying that the parser doesn’t crash on
valid inputs. Luckily, the number syntax is specified in such a way
that a Prolog program easily can be written that generates test inputs.
09. November 2016
Recently while working on Zabavno the emulation was going wrong somewhere in a boot sector and I needed to check what it was actually supposed to be doing. This is pretty easy to do with QEMU as a remote target in gdb, but it can be tricky to get started.
05. November 2016
A certain type of crossword has been catching my attention ever since I was little. But it never interested me much to sit down and solve it on paper. What I wanted to do was to write a program that helps me solve it or, even better, one that finds the solution itself.
26. October 2016
How many bits of information are contained in a routing prefix? When printed, a routing prefix commonly looks like an IP address followed by a slash and then a prefix length: 192.0.2.0/24 or 2001:db8::/32. That should mean a minimum of 32 + ceiling(log2(32 + 1)) = 38 bits for an IPv4 prefix and 128 + ceiling(log2(128 + 1)) = 136 bits for IPv6. However, it is possible to encode a prefix in just one extra bit (for a total of 33 or 129 bits).