Re: Set::setraw error
- To: mathgroup at smc.vnet.net
- Subject: [mg90363] Re: Set::setraw error
- From: David Reiss <dbreiss at gmail.com>
- Date: Mon, 7 Jul 2008 05:07:35 -0400 (EDT)
- References: <g4q9kl$e6o$1@smc.vnet.net>
In statements like a=-a, when the value of a is substituted, you are
attempting to, vor example, evaluat things like
1=-1
which is what is generating your error message.
Some other small suggestions. Use Throw and Catch rather than
Return . You can also use a Which statement rather than the
successive If statements.
Hope this helps...
--David
On Jul 6, 7:17 am, Steven Siew <stevensi... at gmail.com> wrote:
> I have encountered this Set:setraw error for the code below.
>
> I'm stumped. Does anyone have any idea what went wrong?
>
> xgcd[a_,b_]:=Module[{xsign=1,ysign=1,x=1,y=0,r=0,s=1,c,q},
> If[a == 0 && b == 0,Return[{0,0,1}]];
> If[a == 0,Return[{Abs[b],0,b/Abs[b]}] ];
> If[b == 0,Return[{Abs[a],a/Abs[a],0}]];
> If[a<0,a=-a; xsign=-1];
> If[b<0,b=-b; ysign=-1];
> While[b\[NotEqual]0,
> {c,q}={Mod[a,b],Quotient[a,b]};
> {a,b,r,s,x,y}={b,c,x-q*r,y-q*s,r,s}
> ];
> Return[{a,x*xsign,y*ysign}]
> ]
>
> xgcd[2, 3]
>
> \!\(\*
> RowBox[{\(Set::"setraw"\), \(\(:\)\(\ \)\), "\<\"Cannot assign to
> raw \
> object \\!\\(2\\). \\!\\(\\*ButtonBox[\\\"More\[Ellipsis]\\\", \
> ButtonStyle->\\\"RefGuideLinkText\\\", ButtonFrame->None, \
> ButtonData:>\\\"Set::setraw\\\"]\\)\"\>"}]\)