Hello again all.
I've been working away on a (large, complex) software package,
and have a question on programming style. This stems from
a recent post I made to comp.lang.apl about niladic functions:
========== (original query) ==========
> I used the APL niladic function to generate
>tutorials in several versions of APL. When J
>came out I was planning to do the same, but
>was unable to do so because J does not support
>niladic functions.
============ (my response) ===========
You can write a monadic function fun say that ignores its argument,
and call it in J with
fun''
I mainly use niladic functions to return globals, for example
setpc=: 3 : 'PENCOL=: y' NB. usually more complex than this!
getpc=: 3 : 'PENCOL' NB. again may be more complex
NB. e.g. return 0 0 0 if PENCOL undefined
...
p=. getpc'' NB. pen colour
...
As a side-effect of the "idiom" fun'' it's then easy for me
to check when I may be using globals, just by searching for '' .
This technique makes development less error-prone, at least for me
- for example, if (when?) I decide to change PENCOL to be a stack.
========== (further response) ==========
Someone (Markus Triska) then replied saying that
"Passing PENCOL to all functions using it is even less error-prone"
========== (end of extracts) ==========
My experience has been different from Markus's: I know if a
particular function needs access to PENCOL, but keeping track of
"all functions using it" would be a nightmare, particularly in the
development stage (& I expect the development stage to last forever).
I've also found my approach useful whether or not I'm using J's
object-oriented features.
Has anyone any comments? How do other people avoid being strangled
by spaghetti code? (I'm talking several hundred k of .ijs scripts)
Regards, Ewart
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