Matrix from variables

Question

If I defined variables

a=5;
b=3;

what is the fastest/most elegant way to get?

m = [5,3]

Is there something better than

m= Matrix(Eval({a,b}));

And why does

m=[Eval(a),Eval(b)]

not work?

Any links to related posts are welcome :)

hogi · Answer

What do you think about

a=5;
b=3;
m=matrix(a) |/b  //-> works !?!

a combination of all riddles in one expression :)

hogi · Answer

It's amazing that

[](0,1) |/ a |/ b

works. That means, it automatically evaluates the arguments and converts them into a matrix?

a= {{5,3}}
b = {{7 ,6}}
[](0,2) |/ a |/ b

While sharing my learning with my colleagues I noticed:

Up to now, I thought that [a, b] is just a short form of the constructor matrix({a,b}).
But it's the result, right?

Now I really understand what you mean::

@ErraticAttack wrote:

you cannot put expressions in the matrix elements

Then the examples in my last post don't make sense. They just don't work because the matrix() function doesn't have a function to set non-numerical values to "." (missing) - compare the original topic.

By the way:
I am a bit surprised to see the result of matrix(3). Kind of an easter egg ?

hogi · Answer

OK understood.Thanks a lot for the explanation. @ErraticAttack wrote:you cannot put expressions in the matrix elements and expect that it will be populated with the number returned by that expression. Is a good wording :) It could work but you cannot expect that it will work: a=5; matrix(a/b); // -> works
matrix(char(a)) // -> doesn't matrix({char(a)}) // --> doesn't (I hoped this could be a workaround ...)

So .. @ErraticAttack wrote:Expressions are strictly _not_ allowed in matrices, only numbers are allowed. seems to be slightly too strict - but a good approach "to be on the safe side"