February 17, 2008

STRING+ for the rest of us

About two weeks ago Franz, Inc. announced a new string utility function named STRING+ for their Common Lisp implementation.

It embodies the string concatenation paradigm of CONCATENATE, which is orthogonal to that of FORMAT. Some people don’t like FORMAT at all, but I think both have their uses.
I absolutely hate using the concatenation way for doing things like (here in JavaScript/Java/C++):

"You ate " + A + " apples, " + B + " bananas and " + C + " " + OTHER_THING + "."

The way the punctuation marks are placed here drives me totally nuts, and I’d rather prefer a lovely

"You ate ~A apples, ~A bananas and ~A ~A." A B C OTHER_THING

But the former method is useful for building file system paths and URLs, for example (MERGE-PATHNAMES aside).

So basically STRING+ is a shorthand for CONCATENATE ‘STRING. Franz claims speed improvements for small values, but I don’t need that. Short and sweet, here’s the functional equivalent:

(defun string+ (&rest parts)
  (with-output-to-string (out)
    (dolist (part parts)
      (write part :stream out :escape nil))))

Works as advertised, except for the example with the keyword symbol, where case may vary depending on your implementation’s default case conventions (CLISP prints it uppercase).

February 17th 2008 Posted to Lisp,Programming

* Comments(8)

Comments

  1. slobodan
    February 21st, 2008 | 5:23 pm

    string+ is in my toolbox since I started toying with cl-who.

  2. Leslie
    February 21st, 2008 | 5:39 pm

    Ah, where did you get it from?

  3. slobodan
    February 22nd, 2008 | 7:02 pm

    Well I thought about wating for Santa, but considering he pretty much sucks with documentation, christmas was far away, and I’m known for being a bad hm kid. So I hold a meeting with me, myself and I and after a hell of a debate I decided to write it myself. Which I did.

  4. Leslie
    February 22nd, 2008 | 7:42 pm

    Yeah, I know, my question was phrased badly. :) What I actually want to know is, how did you get the idea for this? Did you make it up wholly on your own?

  5. slobodan
    February 26th, 2008 | 9:35 am

    Are you mocking me? For McCarthy’s sake I didn’t made a full blown reverese proxy with per OS load balancers. I made 2 liner utility . For everyone who played with cl-who and and clsql before things like weblocks, elephant, postmodern etc would need such thing to save some typing and got logical mapping of it’s code.

  6. Leslie
    February 26th, 2008 | 10:52 am

    Just different viewpoints, I guess.

    For me, STRING+ isn’t really essential. FORMAT NIL and CONCATENATE ‘STRING did the job well enough.

    I only got the idea for this sometimes-nice-to-have thing when I read Franz’s announcement.

    So basically I was just curious :)

  7. slobodan
    February 26th, 2008 | 2:01 pm

    Could you live without it? Of course.
    Why I made it? Because concatenate is generic thing for concatening sequences, while string+ matches nice into my model. Anyway it proved itself worthy even for a simple wrapper.

  8. Daniel Barlow
    February 26th, 2008 | 6:34 pm

    I have long maintained that + is a silly name for string concatenation: 1+2=2+1=3, not 12. Concatenation isn’t the equivalent for strings, it’s just borrowing a piece of punctuation.

    FWIW, I’ve been using S. for exactly the same thing since forever (I think it’s in Araneida somewhere). #\. is from the Perl operator, #\S is mnemonic for “string” and to avoid gymnastics with input syntax.

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