Multiple assignment between lists in Mathematica 7

Question

Suppose there are two lists a = {a1, a2, a3} and b = {b1, b2, b3}, and I want to write an assignment statement to make a1=b1,a2=b2,a3=b3 which only refers to a and b:

Thread[a = b]

But it only makes a={b1,b2,b3}. Using := (SetDelayed) instead of = doesn't work either.
Any solution? Thanks.

Answer 1

I think the Thread only works on "explicit" lists; the variables need to be expanded before being operated on.

After some experimentation, this works for me:

a = {a1, a2, a3};
b = {b1, b2, b3};
Thread[Set[Evaluate@a, Evaluate@b]];
{a1, a2, a3}

You could also write Thread[Evaluate@a = Evaluate@b]; just depends whichever you find more readable.

Answer 2

What's wrong with

MapThread[Set,{{a1,a2,a3},{b1,b2,b3}}]

?