<div class="gmail_quote">On Fri, Sep 28, 2012 at 3:13 PM, <<a href="mailto:heraklea@gmx.de" target="_blank">heraklea@gmx.de</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Thank you, I write my first lambda ;o). What about this: (define string->mformat (lambda (str) (lambda (n) (lambda (filler) (if (equal? (string-length str) n) str (((string->mformat (string-append filler str)) n) filler)))))) It only prepends, but is this style ok?? </blockquote><div> It depends if you are required to have a particular style (for class, for example), but your code can be rewritten more conveniently (with some subtle differences though) to: (define (string->mformat str n filler) (if (equal? (string-length str) n) str (string->mformat (string-append filler str) n filler))) Equivalently: (define string->mformat (lamda (str n filler) .... )) Some would prefer to use cond instead of if, but in this particular case that's mainly a matter of taste I believe. It is also possible to use build-string, without using explicit recursion: (define (string->mformat str n filler) (string-append (build-string (max 0 (- n (string-length str))) (lambda (x) filler)) str)) Laurent </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Yours, -------- Original-Nachricht -------- > Datum: Thu, 27 Sep 2012 16:26:00 +0200 > Von: Laurent <<a href="mailto:laurent.orseau@gmail.com">laurent.orseau@gmail.com</a>> > An: <a href="mailto:heraklea@gmx.de">heraklea@gmx.de</a> > CC: racket <<a href="mailto:users@racket-lang.org">users@racket-lang.org</a>> > Betreff: Re: [racket] Filling number <div class="HOEnZb"><div class="h5"> > Hi, > > Looking for a friend of real->decimal-string (which does only partly what > you want), I see that the nightly builds include a family of value > formatters like ~a, ~v, etc. > You probably want ~r, for example: > > (~r 42 #:min-width 5 #:pad-string "0") > "00042" > > They have many options that should fit your needs. > > Cheers, > Laurent > > On Thu, Sep 27, 2012 at 4:11 PM, <<a href="mailto:heraklea@gmx.de">heraklea@gmx.de</a>> wrote: > > > Hello friends, > > > > I search the docu, but I cannot find how I can fill a number with > leading > > zeros or trailing zeros. > > > > I am using number->string and would like fill the missing zeros. > > > > Yours, > > ____________________ > > Racket Users list: > > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> > > ____________________ Racket Users list: <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </div></div></blockquote></div>