[tzs]

If a symbol is made of multiple side-by-side ASCII characters, are there any problems telling where one symbol ends and the next starts?

In ordinary text, we separate words with spaces, and add punctuation at the end of sentences to further make the structure apparent. (Well, now we do...a lot of pre-modern writing would justwritethewordssmushedtogetherlikethis [1]). In most of the sample programs in APL successors I've seen there usually didn't seem to be space between symbols.

[1] https://www.bbc.com/culture/article/20150902-the-mysterious-...

[mcguire]

Yes, at least for me, trying to learn it. For example, / in many examples is an "adverb", modifying the previous operator, although xx/ is frequently introduced as a single thing. (Are all built-in verbs one or two characters?)

[gmfawcett]

'xx/' is a single thing -- in the sense that 'xx' is a thing, and '/' is a thing that modifies other things. By applying '/' to 'xx', you get a new, standalone thing.

Re: one-or-two characters, there are a few exceptions, like the folds ( F.. F.: etc.) which are new to J9. Also some older ones like {:: (Map) and &.: (Under) where `x u&.:v y` means `v^:_1 (v x) u v y`. Some of these aren't verbs but conjunctions, adverbs, etc. For the most part they stick to one or two. There are parsing rules that dictate what the second and third characters can be (that's why you see so many colons and periods), and these rules are actually discussed in the JforC book.

Reading J can be tough, as a fellow learner I feel your pain. :) The one that usually gets me (in my own code, even!) is

    5 myverb \ n

...which runs the verb over 5-element slices of 'n' at a time, and joins up the results. The '5' is too far away from the '\', and it can be hard to see the connection right away. I understand why it's so (it's really running the modified verb 'myverb\' with arguments 5 and n) but I still find it hard to read.

When writing my own code, I often leave extra spaces between the multi-character words, and anywhere else that helps legibility. J might be a terse language, but there's no point being crazy about it (unless you're golfing).

[n4r9]

No idea about APL languages but it sounds similar to asking whether the code is uniquely decodable:

https://en.m.wikipedia.org/wiki/Variable-length_code#Uniquel...