Coast-to-Coast revisited
Vector 11:3, page 96
Transcribed from the printed issue; not yet reviewed. Read it in the PDF of the issue, page 96
Please refer to Vector 10.1, page 97 for the background to this note. One of the ideas that I introduced was of managing the Dyalog 'data' property using a pair of functions set_data and get_data to store named variables in any GUI object. I commented at the time that I felt this was a "huge step forward in design" and fitted in well with the APL style we already knew. I started with the assumption that I ought to be able to remove all this code, as namespaces were designed to do precisely the job I had coded around.
If you look first at init_icons (page 101) or init_game (page 105) you can see that as long as you know what your object is called, namespaces clean things up nicely:
[8] 'ttmk'⎕WC'BITMAP' ''bmp cm
[9] ttmk.rtn ttmk.fn ttmk.map←2 'make_term 3' map
[24] BD.ToPlay←'WN' ⍝ Either player may start!
The fun begins when you have the same callback on many objects, so the object name comes in as an argument. Look at rotate_tile on page 104:
This is nasty enough, but putting the data back again gets quite horrible:
[8] bmp set_data ('rtn' rtn)('map' map) ⍝ Old version
[8] ⍎bmp,'.rtn←rtn ⋄ ',bmp,'.map←map' ⍝ New version
I know that Dyadic are working on ⎕CS, to let us shift namespace under program control, so I suppose I will soon be able to write:
... which is better, but leaves me in danger of forgetting to switch back at the end. I think what I really want is something that looks like:
... but I don't hold out much hope of seeing it!