Function that returns 2 BigInts

New to Julia
1

I am having problems with global variables not being visible inside functions also within the main code. So I would like to return 2 BigInts from a function but I dont know how. When I try x = randomfunction() then I get the error “ERROR: LoadError: MethodError: Cannot convert an object of type Vector{BigInt} to an object of type BigInt”

2

Do you have x::BigInt somewhere above? What you’re describing should work just fine

function foo()
    # two BigInts:
    10000000000000000000000, 10000000000000000000000
end 

#######

julia> x = foo()
(10000000000000000000000, 10000000000000000000000)
3

So that returns a tuple…so then I can access it by x[1] and x[2]. I thought I tried this but I will give it another shot tomorrow. Do I define x before assigning it the returned tuple? Should I define x = (0,0) so it knows x should take a tuple? I tried defining it as an array or a vector I think…yeah with ::BigInt…but need to see tomorrow.

4

So that returns a tuple…so then I can access it by x[1] and x[2].

a, b = foo()

is also fine.

Do I define x before assigning it the returned tuple? Should I define x = (0,0) so it knows x should take a tuple?

No need. What you saw above were the only two things I typed in a fresh julia session; nothing else is necessary.

I tried defining it as an array or a vector I think…yeah with ::BigInt…but need to see tomorrow.

A vector is also fine

julia> function foo()
           [big(i) for i in 1:5]
       end
foo (generic function with 1 method)

julia> x = foo()
5-element Vector{BigInt}:
 1
 2
 3
 4
 5
5

Yeah I tried the a, b thing but maybe because a and b were defined as bigints previously it didnt work

6

Why don’t you download Julia onto the device you’re using, so you can play with it right now? It’s free, you know.

7

Ok reproduced the error…the problem is b and c can’t previously be defined. Thanks for the help.

begin
function a()
return BigInt(2),BigInt(3)
end
b::BigInt
b,c=a()
println(typeof(b))
end

8

Can you show some code which illustrates what you mean by this? Perhaps you and I have different ideas of what this means.

b and c are “previously defined” here:

julia> b, c = "hello", "world!"
("hello", "world!")

julia> c, b
("world!", "hello")

julia> function a()
           return BigInt(2), BigInt(3)
       end
a (generic function with 1 method)

julia> b, c = a()
(2, 3)

julia> b, c, b, c, b, c
(2, 3, 2, 3, 2, 3)
9

If you run my code in replit it will not work because of b::BigInt

10

Ah, I see. Yes, in Julia, you cannot simply declare the type of a variable like that. That’s because this syntax is already used for type assertion.

You can, however, declare the type of a variable when assigning it:

julia> function a()
           return BigInt(2), BigInt(3)
       end
a (generic function with 1 method)

julia> b::BigInt, c::BigInt = a()
(2, 3)

To illustrate how the type assertion works:

julia> b::BigInt
2

julia> b::Int
ERROR: TypeError: in typeassert, expected Int64, got a value of type BigInt

Alternatively, you can declare unassigned variables by specifying their scope (with global, local, or let keywords), and then you can also declare their type:

julia> global d::BigInt

julia> d = 5
5

julia> typeof(d)
BigInt

julia> d = "hi"
ERROR: MethodError: Cannot `convert` an object of type String to an object of type BigInt
11

Please try it out so You can see the error it’s the same as My Main code

I am trying to share My code but discourse converts : / to a sade face…