Hello,
This example is a notable use of fry; it would be awkward without it.
I wanted to monitor a directory and update some variables in the current
namespace upon changes made to the directory or it's contents.
The help for 'with-monitors' mentions that the quot is run inside a new scope.
This signals to me that I need to turn my quot into a namespace closure
(vocab: rewrite-closures).
In this example, I'll increment the value of a variable 'a' when changes to a
directory "/tmp/test-dir-105" are made.
Here's some setup:
----------------------------------------------------------------------
USING: threads io.monitors rewrite-closures fry ;
SYMBOL: a
0 a set
: action ( monitor -- monitor )
[ next-change 2drop a get 1 + a set ] [ action ] bi ;
----------------------------------------------------------------------
The code to start monitoring often resembles something like this:
[
[ "/tmp/test-dir-105" t <monitor> action ] with-monitors
]
in-thread
The problem there is that 'action' is run in the scope provided
by 'with-monitors'.
Here's an attempt:
C[ "/tmp/test-dir-105" t <monitor> action ]
[ with-monitors ] curry in-thread
Now the 'action' is inside a quot closed over the current namespace, but this
still doesn't work. The problem is that '<monitor>' needs to be run in the
namespace provided by 'with-monitors'.
So finally, we have this:
C[ action ]
'[
[ "/tmp/test-dir-105" t <monitor> , call ] with-monitors
]
in-thread
This does the job and depends on fry's ability to embed items into nested
quotations.
Ed
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