On 05/30/2012 03:40 PM, Eli Barzilay wrote:
Now, lets imagine that instead of a simple `<>' hole, there are two
kinds of holes with an "up" or a "down" direction -- this leads to
this kind of a syntax:
(○ "foo bar baz"
(substring ↑ 3 8)
(string-trim ↑)
(let ([str ↑]) ↓)
(and (regexp-match? #rx"^[a-z].*[a-z]$" str) ↓)
(string-append "*" str "*"))
where you can read `↑' as "the above" and `↓' as "the below".
It seems like `↑' is another way to not name expressions (i.e. a
"pointless style" :D), and `↓' is handled just fine by internal
definitions. This is equivalent, currently defined, has less nesting,
and avoids a rename:
(define orig-str "foo bar baz")
(define sub (substring orig-str 3 8))
(define str (string-trim sub))
(define m (regexp-match? #rx"^[a-z].*[a-z]$" str))
(and m (string-append "*" str "*"))
A `define*' form like Jay (and I) want would make these kinds of things
less error-prone and allow names to be reused:
(define* ↑ "foo bar baz")
(define* ↑ (substring ↑ 3 8))
(define* str (string-trim ↑))
(define* ↑ (regexp-match? #rx"^[a-z].*[a-z]$" str))
(and ↑ (string-append "*" str "*"))
It's still pretty wordy, though. Even if I had `define*' I'd be tempted
to go with my current favorite idiom, which trades wordiness for a
nesting level:
(let* ([↑ "foo bar baz"]
[↑ (substring ↑ 3 8)]
[str (string-trim ↑)]
[↑ (regexp-match? #rx"^[a-z].*[a-z]$" str)])
(and ↑ (string-append "*" str "*")))
I occasionally get annoyed by how deeply these can get nested. I feel
your pain, man.
Neil ⊥
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