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Ask HN: what's up with HN and Lisp?

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Re: Ask HN: what's up with HN and Lisp?

#11

Post by igneous4 »

SamReidHughes wrote: post #7
igneous4 wrote: post #5

Like many folks, I'd reckon, I've really meant to learn Lisp or Scheme better, but it just seems like -- with the lack of syntax -- it would be tedious to write out every single operation as a function/procedure call. Is Lisp/Scheme as tedious as I'm assuming? I'm not talking about readability -- surely one can get used to the parens and indenting and read (and write) it just fine -- I'm talking about tedium of every…

There's no tedium of writing everything out with parentheses, so you don't need to worry about that. You aren't writing everything "as a procedure call," or at least I wouldn't put it that way. For example, if you write babby's first recursive function in Scheme, (define (factorial n) (if (= n 0) 1 (* n (factorial (- n 1))))) There, the procedure calls are (= n 0), (* n (factorial (- n 1))), (factorial (- n 1)), and…

Thanks for the reply, Sam.

To provide some small examples, I often use Perl, and it gives me some syntax that saves me typing, such as:

* `my @other_list = @a_list[3, 1, 4]` to return just those items from a list (item 3, item 1, and item 4)

* `$str =~ s/$foo/BAR/g` to do string replacements (in string $str, replace all ocurrences of contents of variable $foo with "BAR")

* `my $thing = $colored_objects{red}->[2]` to get item 2 in the list of red-colored objects ($colored_objects is a mapping of color names to lists of items of that color)

* `my $error_msg = "Sorry, but $thing1 doesn't work with $thing2."` to interpolate the values of those 2 variables into the string

* `for (reverse(1 .. 10)) { say "Counting down: $_"; }` (counts down from 10 to 1)

I suppose I've always just guessed that operations like those in a Lisp language would require multiple lines and procedure calls, which would become tedious to write after a while. Is that the case?

Re: Ask HN: what's up with HN and Lisp?

#12

Post by SamReidHughes »

igneous4 wrote: post #11
SamReidHughes wrote: post #7

Earlier quoted context omitted.

There's no tedium of writing everything out with parentheses, so you don't need to worry about that. You aren't writing everything "as a procedure call," or at least I wouldn't put it that way. For example, if you write babby's first recursive function in Scheme, (define (factorial n) (if (= n 0) 1 (* n (factorial (- n 1))))) There, the procedure calls are (= n 0), (* n (factorial (- n 1))), (factorial (- n 1)), and…

Thanks for the reply, Sam. To provide some small examples, I often use Perl, and it gives me some syntax that saves me typing, such as: * `my @other_list = @a_list[3, 1, 4]` to return just those items from a list (item 3, item 1, and item 4) * `$str =~ s/$foo/BAR/g` to do string replacements (in string $str, replace all ocurrences of contents of variable $foo with "BAR") * `my $thing = $colored_objects{red}->[2]` to…

Oh, Perl. In some cases, Lisp would certainly be more verbose. It's probably more tedious than Perl for some things. It also depends on which language you use. Scheme is more tedious than Common Lisp, which is sometimes more tedious than Clojure.

Here are the Clojure equivalents, omitting the act of assigning stuff to variables.

    (map #(a-list %) '(3 1 4))

    ; I'm not modifying x in-place because unfortunately Clojure
    ; doesn't like that.  Common Lisp is more imperative.
     (.replaceAll x foo "BAR")

    ((colored-objects :red) 2)

    (str "Sorry, but " thing1 " doesn't work with " thing2 ".")

    (doseq [i (reverse (range 1 11))]
      (println "Counting down: " i))
If you took the first example and assigned it to a variable other-list, it would typically be in a let expression, with a body.

    (let [other-list (map #(a-list %) '(3 1 4))]
      (subsequent statements that use other-list))

Re: Ask HN: what's up with HN and Lisp?

#13

Post by igneous4 »

SamReidHughes wrote: post #12
igneous4 wrote: post #11

Earlier quoted context omitted.

Thanks for the reply, Sam. To provide some small examples, I often use Perl, and it gives me some syntax that saves me typing, such as: * `my @other_list = @a_list[3, 1, 4]` to return just those items from a list (item 3, item 1, and item 4) * `$str =~ s/$foo/BAR/g` to do string replacements (in string $str, replace all ocurrences of contents of variable $foo with "BAR") * `my $thing = $colored_objects{red}->[2]` to…

Oh, Perl. In some cases, Lisp would certainly be more verbose. It's probably more tedious than Perl for some things. It also depends on which language you use. Scheme is more tedious than Common Lisp, which is sometimes more tedious than Clojure. Here are the Clojure equivalents, omitting the act of assigning stuff to variables. (map #(a-list %) '(3 1 4)) ; I'm not modifying x in-place because unfortunately Clojure ;…

Thanks for those equivalents, Sam! Informative.

That first `(map #...)` is particularly interesting. Looks like you're applying the item lookup operation across the list of indices. Neat.

Re: Ask HN: what's up with HN and Lisp?

#14

Post by SamReidHughes »

igneous4 wrote: post #13
SamReidHughes wrote: post #12

Earlier quoted context omitted.

Oh, Perl. In some cases, Lisp would certainly be more verbose. It's probably more tedious than Perl for some things. It also depends on which language you use. Scheme is more tedious than Common Lisp, which is sometimes more tedious than Clojure. Here are the Clojure equivalents, omitting the act of assigning stuff to variables. (map #(a-list %) '(3 1 4)) ; I'm not modifying x in-place because unfortunately Clojure ;…

Thanks for those equivalents, Sam! Informative. That first `(map #...)` is particularly interesting. Looks like you're applying the item lookup operation across the list of indices. Neat.

The first example could actually have been

    (map a-list [3 1 4])
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