Language Reference Suite

So, as I apply for jobs [I wrote this in 2016], not necessarily in any
particular language, the question of how well I know a language, or what
it means to know a language, comes to mind.  Many languages and standard
libraries are large and have various unique features and idioms, after
all.  But there's a standard useful toolkit one could define: numbers
and strings, control structures, functions and error handling, lists and
maps, objects, I/O.  It'd be cool to do some project that used all of
them for each language, but I can't think of one off hand that I want to
do, and it would probably take longer.  These 'suite' programs are a
more minimalist sequence of code snippets, not doing anything
interesting in themselves, but exercising the various features, to serve
various purposes:

* Evidence to myself and others that I know how to do X in a language.
* One-stop documentation for myself on how to do X, if I forget.
* Documentation of things I expected to work, but don't.
* Checklist for learning a future language.

Status: I'm not sure any language set is done.  Maybe the C one.  Other
things came up, like having an actual job...

Language basics:
comparisons and if tests
loops: for, while, sequence iteration.
math: modular, power, complex
strings: create, compare, modify, copy, substrings, splitting
functions: closures, function objects, funky parameters
arrays or lists: initialize, copy, resize, split
multiple dimensional arrays

More language:
maps
bits
array of maps, map of arrays, map of maps
priority queue
objects
assertion
library sort, search
applicative functions
handrolled sort
exceptions or errors
regular expressions
threads, locks
package or modules, build

Basic IO:
console io: read, write, error
file io: file existence, creation, reading, writing, deletion
get time (epoch and clock)
get random numbers
get date

More IO
directory functions
sockets and networking
database access
link against libraries