nimforum mirror - about module vars

yohanip (orginal) [2026-02-07T04:38:45+01:00] view original

Hello there great community i am currently learning nim, and got stuck with this one, please kindly help..

The main idea is when passing parent as none to the newA proc, we will use the module var: root as the parent but somehow if i am passing parent as none(A) to the newA proc, it will return incorrect len, but it will display correct result if passing as some(root)

Thank you friends

i have a main.nim:


import options
import a

let child = newA(none(A), some("child a")) # <-- using this line i will get incorrect result
# let child = newA(some(root), some("child a")) <-- if using this line i will get the correct len
discard newA(some(child), some("child b"))

echo "@root:", root.children.len  # expecting 1
echo "@child a:", child.children.len # expecting 1

and in a.nim


import options

type A* = ref object
    name: Option[string]
    parent: Option[A]
    children*: seq[A]

var root* = A(
        name: some("root"),
        parent: none(A),
        children: @[]
    )

proc add_child*(self: A, child: A) =
    self.children.add(child)
    child.parent = some(self)

proc newA*(parent: Option[A], name: Option[string] = none(string)): A =
    var new_child = A(
        name: name,
        parent: parent,
        children: @[]
    )
    
    if parent.isNone():
        echo "adding to root"
        root.add_child(new_child)
    else:
        echo "adding to child"
        parent.get().add_child(new_child)
    
    return new_child

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