On Sat, Apr 11, 2020 at 11:02:39PM +0200, Otto Diesenbacher-Reinmüller wrote:
1 chunk monkey
I would write it as {(+\(⍴,⍵)⍴⍺↑1)⊂,⍵}.
(In low-⎕ML Dyalog it would be {((≢⍵)⍴⍺↑1)⊂,⍵} without needing that +\
on left argument.)
You can write ≢⍵ or ⍴,⍵ here, using ≢ is probably more idiomatic in
Dyalog and works just as fine in GNU APL. Forcing right argument
into a vector using ravel should be enough to handle scalars without
any additional branching.
→((0=≢⍴a)∧1=≢a)/skalar ⍝ matches a skalar, but not ''
This is redundant as 0=≢⍴a implies 1=≢a.
Note that '' is not a scalar but a vector of length zero.
The notation for character literals is confusing, I know.
Checking for types is not easy. 0=⍴N is a scalar. Howto check for a
string?
"String" usually means a "vector of characters". You already know how
to check a rank (I suppose it's just a typo and you meant 0=⍴⍴N or maybe
0=≢⍴N for a scalar, i.e. an array of rank zero) and vector is just an
array of rank one.
The closest thing to what can be informally called a type of an array is
its typical element (also called fill element or a prototype). For
simple numeric arrays the typical element is zero, for simple character
arrays it is a blank. You can use it like this:
0≡↑0⍴X ⍝ X is numeric (if simple)
' '≡↑0⍴X ⍝ X is a character array (if simple)
So it would be something like (1=⍴⍴X)∧' '≡↑0⍴X to check for a "string".
Or maybe (1≥⍴⍴X)∧' '≡↑0⍴X if you wanted to include character scalars
like 'a' in the definition of a "string". It will nevertheless fail if
your array is mixed because those have implementation-defined typical
elements, so you might want to check depth and every element:
∧/(1=⍴⍴X),(1≥≡X),{' '≡↑0⍴⍵}¨X
(In case of Dyalog replace monadic ↑ with ⊃ as needed depending on the
value of ⎕ML)
You won't really need checks like that. Just write your code assuming
your data is of the right "type" and let some primitive throw a domain
error if it isn't. If you need to accept vectors but also pretend that
scalar is a one-element vector, just ravel it.
-k
