[plt-scheme] Printing

1. We did see your email. I don't know about Internationalization of  
numerics in drscheme. Robby might.

2. This line is wrong in my email:

>             (char=? (string-ref str (- (string-length str) n 1) #\.))))

How this happens I don't know. I use this module on an almost daily  
basis. I suspect my cut and pasted mangled something.

-- Matthias




On Mar 1, 2006, at 4:03 PM, Evangelos Tsagkas wrote:

> Before going on, i apologize for "hijacking" this thread. i did this
> because it seems i have some problems posting directly to the list. i
> did try it some time back (DrScheme v.2xx) and neither did i see my
> message in the list nor did i get an answer. i just tried it again
> about an hour ago and though i'm not impatient, i'm not sure anybody
> received my message with the subject "Numbers and i18n". if you did,
> accept this apology.
>
> However, i have something to contribute to this thread as well. i
> tried the module you posted and
>   (number->format-decimal 3.145 2)
> comes back with
>   string-ref: expects 2 arguments, given 3: "3.14" 1 #\.
> in v.301.7
>
> i will not go ahead with what i wrote in the message concerning
> internationalization and numbers, as i cannot be sure i'm not flooding
> the list.
>
> If you did not receive that message and you have some idea as to what
> i'm doing wrong (or why i cannot seem to find a way to have my mailing
> list password emailed to me)-: i would appreciate your pointers.
>
> -- evangelos
>
>
> On 10/15/05, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
>> This is a part of my collects, with contracts and friends, used in a
>> quotster and stock evaluation program. I have meant to put such
>> "contracted" code up at Planet for a while, but time just disappears.
>> -- Matthias
>>
>>
>> (module decimals mzscheme
>>
>>    (require
>>     (lib "string.ss" "srfi" "13")
>>     (lib "contract.ss"))
>>
>>    ;; Number Natural -> String -> Boolean
>>    ;; is the decimal point at the right place in the string
>>    (define (post-number->format-decimal _ n)
>>      (define (formatted-number-as-string str)
>>        (and (string? str)
>>             (char=? (string-ref str (- (string-length str) n 1)  
>> #\.))))
>>      formatted-number-as-string)
>>
>>    ;; Any -> Boolean
>>    (define (real-or-rational x)
>>      (or (inexact? x) (integer? x) (real? x)))
>>
>>    (provide/contract
>>
>>     [number->format-decimal
>>      ;; convert a number into a formatted decimal string
>>      ;; given: 10.321 wanted: "10.32"
>>      ((flat-named-contract 'real-or-rational real-or-rational)
>>       natural-number/c
>>       . ->d .
>>       post-number->format-decimal)]
>>
>>     [number->decimal-string
>>      ;; convert a number into a decimal string
>>      (number? . -> . string?)])
>>
>>    ;; Number N -> String
>>    ;; turn the number x into a string with num digits after the  
>> decimal
>> point
>>    (define (number->format-decimal x num)
>>      (let ([split (regexp-match "([0-9]*)\\.([0-9]*)"
>> (number->decimal-string x))])
>>        (format "~a.~a" (cadr split) (string-pad-right (caddr split)  
>> num
>> #\0))))
>>
>>    ;
>> ---------------------------------------------------------------------- 
>> --
>> ---
>>    ; Number -> String
>>    ; turns a number into a string with decimal representation
>>    ; Matthew's code
>>    (define (number->decimal-string x)
>>      (cond
>>        [(or (inexact? x) (integer? x)) (number->string x)]
>>        [(not (real? x)) ;; complex
>>         (let ([r (real-part x)]
>>              [i (imag-part x)])
>>          (format "~a~a~ai"
>>                   (number->decimal-string r)
>>                   (if (negative? i) "" "+")
>>                   (number->decimal-string i)))]
>>        [else
>>         (let ([n (numerator x)]
>>               [d (denominator x)])
>>           ;; Count powers of 2 in denomintor
>>           (let loop ([v d][2-power 0])
>>             (if (and (positive? v) (even? v))
>>                 (loop (arithmetic-shift v -1) (add1 2-power))
>>                 ;; Count powers of 5 in denominator
>>                 (let loop ([v v][5-power 0])
>>                   (if (zero? (remainder v 5))
>>                       (loop (quotient v 5) (add1 5-power))
>>                       ;; No more 2s or 5s. Anything left?
>>                       (if (= v 1)
>>                           ;; Denominator = (* (expt 2 2-power) (expt 5
>> 5-power)).
>>                           ;; Print number as decimal.
>>                           (let* ([10-power (max 2-power 5-power)]
>>                                  [scale (* (expt 2 (- 10-power  
>> 2-power))
>>                                            (expt 5 (- 10-power
>> 5-power)))]
>>                                  [s (number->string (* (abs n)  
>> scale))]
>>                                  [orig-len (string-length s)]
>>                                  [len (max (add1 10-power) orig-len)]
>>                                  [padded-s (if (< orig-len len)
>>                                                (string-append
>>                                                 (make-string (- len
>> orig-len) #\0)
>>                                                 s)
>>                                                s)])
>>                             (format "~a~a.~a"
>>                                     (if (negative? n) "-" "")
>>                                     (substring padded-s 0 (- len
>> 10-power))
>>                                     (substring padded-s (- len  
>> 10-power)
>> len)))
>>                           ;; d has factor(s) other than 2 and 5.
>>                           ;; Print as a fraction.
>>                           (number->string x)))))))])))
>>
>> _________________________________________________
>>   For list-related administrative tasks:
>>   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>>
>
>
> --
> if feeling is first who pays any attention to the syntax of things
> will never wholly kiss you
> -- ee cummings