Added a second example inside the `typedthreads` file.
Also, add a more detailed introduction. When Nim is one's first
programming language, a short explanation of what a thread is might not
hurt.
For reference, the thread documentation of other languages looks like
this:
- https://en.cppreference.com/w/cpp/thread/thread
- https://doc.rust-lang.org/std/thread/
The documentation of a module is the first place one will look when
using a standard library feature, so I think it is important to have a
few usable examples for the main modules.
This is the example added
```nim
import locks
var l: Lock
proc threadFunc(obj: ptr seq[int]) {.thread.} =
withLock l:
for i in 0..<100:
obj[].add(obj[].len * obj[].len)
proc threadHandler() =
var thr: array[0..4, Thread[ptr seq[int]]]
var s = newSeq[int]()
for i in 0..high(thr):
createThread(thr[i], threadFunc, s.addr)
joinThreads(thr)
echo s
initLock(l)
threadHandler()
deinitLock(l)
```
Sharing memory between threads is very very common, so I think having an
example showcasing this is crucial.
---------
Co-authored-by: Andreas Rumpf <rumpf_a@web.de>
2bd2f28858