artemiogr97 Posts - Answer Overflow

artemiogr97

•Created by artemiogr97 on 4/14/2024 in #questions

Optional string argument

Is there a simple way to create a function that takes an optional String argument with no default value (assigned to None) ? I tried the following:

fn my_func(my_string: Optional[String] = None)-> String:
    ...

fn my_func(my_string: Optional[String] = None)-> String:
    ...

this works for a String but calling the function with a StringLiteral does not: my_func("my_string") gives the following error invalid call to 'my_func': argument #0 cannot be converted from 'StringLiteral' to 'Optional[String]' I guess one way to make it work for now is to use a default value as follows:

fn my_func(my_string: String = "my_default_string")-> String:
    ...

fn my_func(my_string: String = "my_default_string")-> String:
    ...

But this does not allow to distinguish between a bad input and an empty imput

17 replies

MModular

•Created by artemiogr97 on 4/4/2024 in #questions

Lifecycle doc clarification

I was reading https://docs.modular.com/mojo/manual/lifecycle/life#move-constructor, the following struc is given as an example:

struct HeapArray:
    var data: Pointer[Int]
    var size: Int

    fn __init__(inout self, size: Int, val: Int):
        self.size = size
        self.data = Pointer[Int].alloc(self.size)
        for i in range(self.size):
            self.data.store(i, val)

    fn __copyinit__(inout self, existing: Self):
        # Deep-copy the existing value
        self.size = existing.size
        self.data = Pointer[Int].alloc(self.size)
        for i in range(self.size):
            self.data.store(i, existing.data.load(i))

    fn __moveinit__(inout self, owned existing: Self):
        print("move")
        # Shallow copy the existing value
        self.size = existing.size
        self.data = existing.data
        # Then the lifetime of "existing" ends here, but
        # Mojo does NOT call its destructor

    fn __del__(owned self):
        self.data.free()

struct HeapArray:
    var data: Pointer[Int]
    var size: Int

    fn __init__(inout self, size: Int, val: Int):
        self.size = size
        self.data = Pointer[Int].alloc(self.size)
        for i in range(self.size):
            self.data.store(i, val)

    fn __copyinit__(inout self, existing: Self):
        # Deep-copy the existing value
        self.size = existing.size
        self.data = Pointer[Int].alloc(self.size)
        for i in range(self.size):
            self.data.store(i, existing.data.load(i))

    fn __moveinit__(inout self, owned existing: Self):
        print("move")
        # Shallow copy the existing value
        self.size = existing.size
        self.data = existing.data
        # Then the lifetime of "existing" ends here, but
        # Mojo does NOT call its destructor

    fn __del__(owned self):
        self.data.free()

what does Then the lifetime of "existing" ends here, but Mojo does NOT call its destructor mean? I understand that existing.data must not be free but what about existing.size? is it freed even though the destructor is not called? in theory a copy was made by doing self.size = existing.size

5 replies

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