^[81] The POSIX standard for regular expressions introduces some symbolic ranges like [[:lower;;]] and [[:digit:]], and some specific tools have extra wildcards not covered here, but these will suffice to interpret most regexps.

^[82] For non-Unix programmers, an X toolkit is a graphics library that supplies GUI widgets (like labels, buttons, and pull-down menus) to the programs that link to it. Under most other graphical operating systems, the OS supplies one toolkit that everyone uses. Unix and X support multiple toolkits; this is part of the separation of policy from mechanism that we called out as a design goal of X in Chapter1. GTK and Qt are the two most popular open-source X toolkits.

^[83] Whether or not “macro expansion” should be spelled “macroexpansion” is a matter for some dispute. The latter is found mainly among Lisp programmers.

^[84] It is not clear that XSLT could be any simpler and still do its job, however, so we cannot characterize it as a bad design.

^[85] XSL Concepts and Practical Use.

^[86] https://www.netlib.org/

^[87] It is also quite traditional for Unix books that describe pic(1) to include their own illustrations as coding examples.

^[88] The line is owed to Alan Perlis, who did some of the pioneering work in software modularity around 1970. The semicolon in question was the statement separator or terminator in various Algol-descended languages, including Pascal and C.

^[89] For those who have never programmed in a modern scripting language, a dictionary is a lookup table of key-to-value associations, often implemented through a hash table. C programmers spend a lot of their coding time implementing dictionaries in various elaborate ways.

^[90] I was at one time an awk wizard, but I had to be reminded by someone else that the language was applicable to the HTML-generation problem where this book's only awk example occurs.

^[91] There is a GhostScript Project site.

^[92] A First Guide To PostScript.

^[93] One of the silliest things you can do with a modern Unix machine is run the Eliza mode of Emacs against random quotes from Zippy the Pinhead. M-x psychoanalyze-pinhead; type control-G when you've had enough.

^[94] Open-source JavaScript implementations in C and Java are available.