Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!mcsun!hafro!isgate!krafla!karlth
From: karlth@rhi.hi.is (Karl Thoroddsen)
Newsgroups: comp.lang.pascal
Subject: Re: Brain Teaser
Summary: Does a solution exist?
Message-ID: <1207@krafla.rhi.hi.is>
Date: 16 Oct 89 13:18:18 GMT
References: <none> <727@thor.wright.EDU> <1989Oct5.213548.13466@wuee1.wustl.edu>
Organization: University of Iceland
Lines: 53

In article <1989Oct5.213548.13466@wuee1.wustl.edu>, jtw@wuee1.wustl.edu (Trent Wohlschlaeger) writes:
> In article <727@thor.wright.EDU> demon@thor.wright.edu writes:
> >	Write a routine that will convert from one base to another.
> >function convert(base : integer; input_num : string) : string;
>                   ^^^^
> > Might I suggest:
> 
> function convert(inbase, outbase : integer; input_num : string) : string;
> 
> I would be more impressed with code that does this directly, rather
> than converting to base 10 (or 2, or 16, or...) first.
> 
> For example, convert 10110101 base 4 to x base 7.
> 
> x:= convert (4, 7, "10110101");
> 
> Trent

A solution to the problem of converting from one base to another is  
 fairly straightforward (solution follows).

But as Trent says it would be much more impressive if the routine would
convert directly, can anyone program a routine which does that?

-----------------------CONVERT ROUTINE TP 5.0------------------
{FOR BASE >1 and <17}

function power(x,y:longint):longint;
var pow : longint;
begin pow:=1;
while y>0 do begin
  pow:=pow*x;dec(y);end;
power:=pow;
end;

function convert(in_base,out_base:integer;in_num:string):string;
const num_char = '0123456789ABCDEF';
var count,sum,num:longint;Out_num:string;
begin
sum:=0;count:=1;num:=0;Out_num:='';
while not(count>length(in_num)) do begin
  num:=pos(copy(in_num,count,1),num_char)-1;
  sum:=num*power(in_base,length(in_num)-count)+sum;
  inc(count);{ count:=count+1}
  end;       { Of convert to 10 base}
while sum>0 do begin
  out_num:=concat(copy(num_char,(sum mod out_base)+1,1),out_num);
  sum:=sum div out_base;
  end;
 
convert:=out_num;
end;