Re: [PATCH v1 1/6] docs/match: add pattern matching examples

[Maxime Devos]

On 26-01-2023 19:57, Blake Shaw wrote:
>   @example
> -(match lst
> -  (((heads tails ...) ...)
> -   heads))
> +(match '(((a b c) e f g) 1 2 3)
> +  (((head ...) tails ...)
> +   `(,@tails ,head)))
> +@result{} (1 2 3 ((a b c) e f g))
>   @end example


Contrary to the commit message, this isn't an addition of a pattern 
matching example, it's a change.
Aside from inlining 'lst', what's this change for?

> +A pattern matcher can match an object against several patterns and
> +extract the elements that make it up. 
> +
> +@example
> +(let ((m '((a . b) (c . d) (e . f))))
> +  (match m
> +    (((left . right) ...) left)))
> +@result{} (a c e)
> +@end example

There is only a single pattern here, not several patterns.
Several patterns would be, e.g.,

(let ((m '(#(a b) #(c d) #(e f)))
  (match m
    (((left . right) ...) left)
    ((#(left right) ...) left))).

> +Patterns can represent any Scheme object: lists, strings, symbols,
> +records, etc.

Missing end-of-sentence period. The . in 'etc.' is part of the 
abbreviation 'etc.', not an end-of-sentence marker.  I know it's 
'standard' English (for some value of 'standard' in English) to conflate 
all the dots, but we don't have to follow standard when they are buggy.

(This is like the example at 
<https://catb.org/jargon/html/writing-style.html> about not moving the 
end-of-sentence period inside quotation marks:

    Then delete a line from the file by typing “dd”.

    Then delete a line from the file by typing “dd.”

-- while in this particular case (i.e., 'etc.') the distinction is 
unimportant, for consistency with other cases where the distinction is 
important, I would go for '..., symbols, records, etc..'.


Greetings,
Maxime.

OpenPGP_0x49E3EE22191725EE.asc
Description: OpenPGP public key

OpenPGP_signature
Description: OpenPGP digital signature