>Though I do think there is a bug here -- you cannot exit the
>interpreter until the right parenthesis line is provided.
This is a hack I've used since my early days of J. You can use explicit
definition entry to spy on what actions J is taking "behind the scenes". First,
enter this line in J:
0 : 0
Now, while J is "hung", take a GUI action. Try to close J, for example. Now
type:
)
And you'll see:
wdhandler_0_''
This was neater in J4 when all the wd calls were not encapsulated so. You
could see what code a function key was actually executing, or what code to use
to minimize a window, etc. I bet you could still use it to spy on systimer
and DLL callbacks.
-Dan
PS: You're right, "noun" was correct.
I thought that the verb definition would be held in suspense until its argument
was provided, which would never occur because the engine would see two nouns
juxtaposed (the rank-1 array of boxes and the empty string) and signal error.
But I forgot that immediately upon matching a Section II.E production, J pops
the stack & executes the results. So, since $ verb noun is a relevant
production, it's executed before the engine even notices the noun noun error.
This can be demonstrated with
3 : 0 'hello' 'error'
smoutput toupper y.
)
HELLO
|syntax error
| 3 :0'hello''error'
This syntax error is not due to the juxtaposition 'hello' 'error' but instead
'HELLO' 'error' .
This is fertile ground for bug hunting.
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