CODEWITHSUNDEEP
for-loopmaple
Lecter
Lecter

Reputation: 123

Basic question from a beginner. Problem with definitions in a bucle. Maple

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.

Upvotes: 0

Views: 59

Answers (1)

acer
acer

Reputation: 7246

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.

Upvotes: 1

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