View source for Talk:Permutations with repetitions

==Mathematica solution incorrect?==
The task description says combination must be produced one at a time.
The Mathematica solution uses Tuples, which return a list of all permutations at once.
Is this a correct solution?
--[[User:Soegaard|Soegaard]] ([[User talk:Soegaard|talk]]) 14:16, 21 May 2013 (UTC)

==REXX implementation limits==

Most REXX interpreters have implementation limits on the length of a REXX clause.

For Regina REXX, it depends on the release level.

For Regina REXX 3.3, &nbsp; 3.4, &nbsp; 3.5, REXX gives a SYNTAX error:

:::::: Error 12 running "C:\xxxxxx.REX", line 29: [Clause &amp; 1024 characters]

For Regina REXX 3.6, &nbsp; 3.7, REXX "crashes" somewhere less than a statement length of 1932,
<br>I haven't pursued this to find the exact byte count.

{By crashing, I mean Microsoft Windows displays a small error "window":

:::::: Regina Rexx Launcher (x86) has encountered a problem
:::::: and needs to close. &nbsp; We are sorry for the inconvenience.
:::::: (more boilerplate follows).

For what's it worth, I believe REXX should raise the SYNTAX condition.

[The reason I mention the older versions of Regina REXX is that Regina 3.3 REXX uses less
<br>virtual memory for those REXX programs which use a ''lot'' of stemmed variables (possibly a
<br>memory leak), so the use of the older Regina release is forced in lieu of a fix.   

For PC/REXX and Personal REXX, it depends on what the RXISA ('''SET''' environmental variable).
<br>These two REXXes either give:
:::::: Error 11 on line 29 of c:\xxxxxx.REX" Control stack full
<br>
:::::: Memory full: symbol
:::::: Error 5 on line 29 of C:\xxxxxx.REX: Machine resources exhausted

somewhere between 568 and 597 bytes.  

It should be noted that most people use the maximum for the RXISA &nbsp; (which is 40K).

As far as I can tell, R4 and ROO have no (real) limitation for the length of an INTERPRET instruction,
<br>and that is probably true of CMS REXX and TSO REXX &nbsp; (it's been too long since I used those
<br>two flavors of REXX).   

::::::::::: -- [[User:Gerard Schildberger|Gerard Schildberger]] ([[User talk:Gerard Schildberger|talk]]) 20:2013 (UTC)

----

==another variant of the REXX example==
This REXX version:
* simplifies many statements
* minimizes the length of the INTERPRET statement
* eliminates the SELECT statements
* eliminates a DO loop
* uses both kinds of quotes strings to make it easier to peruse
* moves a couple of statements out of the INTERPRET clause
* uses a positive (logic) instead of a negative IF statement
* eliminates an extra &nbsp; ''';''' &nbsp; (semicolon) from the INTERPRET clause
* eliminates the need for counting the permutations
<br>If any of these improvements could/would be of use, that's fine. &nbsp; I plan to delete this entry in a couple of weeks. -- [[User:Gerard Schildberger|Gerard Schildberger]] ([[User talk:Gerard Schildberger|talk]]) 04:2013 (UTC)
<lang rexx>/*REXX*/ parse arg n m s names
if n=''  then n=3
if m=''  then m=2
if datatype(s,'N')  then s=left('',s)
 
        do k=1 to n
        if names=''   then e.k=k
                      else parse var names e.k names
        end   /*k*/
a=''
                    do i=1 to m;   a=a'do d'i"=1 to n;";   end  /*i*/
a=a'z=e.d1'
                    do j=2 to m;   a=a"||s||e.d"j;         end  /*j*/
 
a=a';say z'copies(";end",m)
if m==0  then do; say '1 permutation, a "null".'; exit; end
interpret a
say  n**m  'permutations'</lang>

== Isn't it just similar to "Increment_a_numerical_string" ==

You set the length of the string to n fill it completly with "0" and set the base to k.
http://rosettacode.org/wiki/Increment_a_numerical_string#Pascal
Of course you can use an array of integer instead.