Hello!

I am a real beginner in Sage, I have just started th use it. In fact this is my first programing language, so I have some difficulties with it... Now I needed a command, which determins all the k-element subset of [1,2,...,N]. Since I don't found a command like this, I decided to write a program... :-) And now I simple don't understand while my program doesn't work corrrectly! Could you explain me? It is a bit longish, so sorry for this.

def eve(A,N): #the largest elem in the list A which can be increased by 1, such that the resulting list contains only different elements less than N. Originally A should contain different elements in increasing order.

```
ev=len(A)-1
while A[ev]==ev+N-len(A):
ev=ev-1
return ev
```

def rakovetkezo(A,N): # Increases the eve(A,N)nt element by 1, and all the other elements after this element are succesive natural numbers

```
Q=A
ev=eve(Q,N)
x=Q[ev]
for i in range(ev,len(Q)):
Q[i]=x+i-ev+1
return Q
```

def reszhalmazok(N,k): #It should (but it doesn't) return the k-element subset of [1,2,...,N]

```
X=range(k)
B=[range(k)]
ev=eve(X,N)
while ev!=-1:
X=rakovetkezo(X,N)
B.append(X)
ev=eve(X,N)
return B
```

Now reszhalmazok(5,3) should return [[0,1,2], [0,1,3],...] but it returns something completely different, aaand I don't see why, and how could be improve it?

Katika