I have participated in projects in which there are
hundreds of globals. Passing all of them as
arguments would be really complicated.
On the other hand, there have been a few times when
I got burned as where f called g and g changed a
global which then wrecked things for f . I solved
the problem as follows:
g=: 3 : 0
old=. global
global=: new
blah blah blah
global=: old
result
)
----- Original Message -----
From: Ewart Shaw <[EMAIL PROTECTED]>
Date: Monday, September 11, 2006 5:29 am
Subject: [Jprogramming] Developing large projects
> 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)
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