Qfyilyi

Let's suppose we are in this case (I'm using Maple)

add:=function()

e1:=0;

e2:=1;

for j in [1..2]do

ej:=ej+1

od;

return e1,e2;

end;

This program gives me a global variable error. I understand why that happens -- because ej is not defined as local -- but if you define it then the program just doesn't do anything. ) I don't know how to solve it. My objective (in a bigger program) is to call e1,e2 in a for loop.

Maybe I didn't express myself correctly simplifying my problem, there is my Program, it is made with program GAP but it works similar to Maple:

G12Decode:=function(c)

localx,G,C,sG,sH,a,u,b1,e1,b2,e2,b3,e3,b4,e4,b5,e5,b6,e6,h1,h2,i,j; 

x:=Codeword(c,GF(3));

G:=[[1,0,0,0,0,0,0,1,1,1,1,1],[0,1,0,0,0,0,1,0,1,2,2,1], 

[0,0,1,0,0,0,1,1,0,1,2,2],[0,0,0,1,0,0,1,2,1,0,1,2], 

[0,0,0,0,1,0,1,2,2,1,0,1],[0,0,0,0,0,1,1,1,2,2,1,0]];

C:=GeneratorMatCode(G,GF(3));

sG:=x*TransposedMat(GeneratorMat(C));

sH:=x*TransposedMat(CheckMat(C));

a:=[0,0,0,0,0,0];

b1:=Codeword([0,1,1,1,1,1],GF(3)); 

e1:=Codeword([1,0,0,0,0,0],GF(3));

b2:=Codeword([1,0,1,2,2,1],GF(3)); 

e2:=Codeword([0,1,0,0,0,0],GF(3));

b3:=Codeword([1,1,0,1,2,2],GF(3)); 

e3:=Codeword([0,0,1,0,0,0],GF(3));

b4:=Codeword([1,2,1,0,1,2],GF(3)); 

e4:=Codeword([0,0,0,1,0,0],GF(3));

b5:=Codeword([1,2,2,1,0,1],GF(3)); 

e5:=Codeword([0,0,0,0,1,0],GF(3));

b6:=Codeword([1,1,2,2,1,0],GF(3)); 

e6:=Codeword([0,0,0,0,0,1],GF(3));



if Weight(sH)<=2 then

sH:=ShallowCopy(VectorCodeword(sH));

Append(a,sH);

a:=Codeword(a,GF(3));

u:=x-a;

return u;

elif Weight(sG)<=2 then

sG:=ShallowCopy(VectorCodeword(sG));

Append(sG,a);

sG:=Codeword(sG,GF(3));

u:=x-sG;

return u;

else

for i in [1..6] do

for j in [1..6] do

if sG-bi=ej or sG-bi=2*ej then 

h1:=sG-bi;

h2:=ei;

h1:=ShallowCopy(VectorCodeword(h1));

h2:=ShallowCopy(VectorCodeword(h2));

Append(h1,h2);

h1:=Codeword(h1,GF(3));

u:=x-h1;

return u;

elif sG-2*bi=ej or sG-2*bi=2*ej then

h1:=sG-2*bi;

h2:=ei;

h1:=ShallowCopy(VectorCodeword(h1));

h2:=ShallowCopy(VectorCodeword(h2));

Append(h1,h2);

h1:=Codeword(h1,GF(3));

u:=x-h1;

return u;

fi;

od;

od;

fi;

end;

The program dont send me an error but i know it don't work because of the ej,bi and ei. I want to do what it says after the last "else" but i don't know how to solve it to make it work.

Your syntax is invalid. It is proc, not function.

And add is already a Maple command, so it's a protected name and cannot be assigned to. You have to use another name.

And your syntax for the do-loop is likely not what you want. You probably want for j from 1 to 2 do .

And you really should initialize ej with a value before doing the recursive assignment ej:=ej+1 .

And you might as well declare the procedure's local variables.

Personally, I favour using end do instead of od , and end proc instead of just end , in modern Maple. It makes it easier to tell what's being terminated.

For example,

restart;



my_add:=proc()

  local e1,e2,ej,j;

  e1:=0;

  e2:=1;

  ej:=0;

  for j from 1 to 5 do

    ej:=ej+1

  end do;

  return ej,e1,e2;

end proc:



my_add();



                 5, 0, 1

There is a Maple Programming Guide, which you can read online or inside Maple's own Help system. It has a nice introduction to writing procedures. And there is a more detailed Help page for the proc command.