Reassigning N affects later execution of mod but not verbs created
previously by mod:
mod =: 1 : 'N&|@:x'
N =: 5
mod5double =: +: mod
mod5double 4
3
N =: 7
mod5double 4
3
mod7double =: +: mod
mod5double 4
3
mod7double 4
1
Henry Rich
On 3/9/2019 10:32 AM, Jan-Pieter Jacobs wrote:
Hi!
There's a fairly substantial problem with chapter 32 of FSOJ, as it uses
this definition for mod:
mod=: adverb : 'n&|@x'
Aside the fact that using it as defined yields a domain error (easily
solved using N instead of n), there is a problem where afterwards the
article seems to assume that reassigning n (or N) influences mod.
However, it does not (at least in recent J), and would need redefining mod
every time a different N is used.
Would replacing mod by the following definition be acceptable:
mod =: 2 : 'n&|@u' ? It is then used as (^ mod 10) for modulo 10
exponentiation, for instance.
What do you think?
Best regards,
Jan-Pieter
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