Learning J from using and observing the utils 
Author Message
 Learning J from using and observing the utils

I finf that the best way to learn J is to use the utilities that come
with J and then once in a while look at how one particular utility is

Take one of the most useful utility in Visual J, "wdinfo"

This is a simple little verb and yet so powerful and useful

You can give it a string and it will display it on the screen.
Give it a boxed array and it will give you a title as well.

NB. syntax: wdinfo [title;] message

gives me a box titled "Hallo" and inside the box is little icon and the
text "Gosi". It is very impressive to present this to onlookers.

Give it a three (or more) item box and only the last two are used.
gives the same results as the one above.

Now look at the verb:

  wdinfo=: 3 : 0
NB. syntax: wdinfo [title;] message
'ab'=. _2{. boxopen y.
if. 2=#$b=. ":b do. b=. }.,LF,.b end.

empty wd 'mb ',(f a),' ',(f b),' mb_iconinformation'

The first line is a comment with the syntax (important) and then the
first line to execute picks the text from the user:
'ab'=. _2{. boxopen y.

Now "a" hold the optional title and "b" the text to be placed in the

The last line calls windows and puts the text out plus the icon.

I am not suggesting to learn everything from the verb at the first
look into it. Pick out and learn a few of the techniques used and
try to figure out what the verb is doing. I find it stimulating
and it gives me ideas for my own coding.


http://www.*-*-*.com/ ~gosi

Tue, 29 Sep 1998 03:00:00 GMT  
 [ 1 post ] 

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