C#•7mo ago

Help understanding some code

I am following along with a tutorial on YouTube for AStar. There is one portion of the code that does not make sense. I will do my best to highlight the code and explain why it does not make sense. First, we take a look at the node class. From my understanding of this code (I am not fluent in CS) it seems like g and h cost are left uninitialized. https://github.com/SebLague/Pathfinding/blob/master/Episode%2003%20-%20astar/Assets/Scripts/Node.cs Knowing that gCost and hCost are never initialized, I assume that it is initialized later on. But I can not seem to find where this happens. In the main pathfinding function for AStar implementation, the code magically used the gCost value in an evaluation (Line 46). But how could it exist? Furthermore, let's consider it was magically initialized to some arbitrary number, that doesn't represent a valid gCost in the aStar algorithm. Realistically the gCost would not be known until a neighbour observed it... https://github.com/SebLague/Pathfinding/blob/master/Episode%2003%20-%20astar/Assets/Scripts/Pathfinding.cs

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Pathfinding/Episode 03 - astar/Assets/Scripts/Node.cs at master · S...

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Pathfinding/Episode 03 - astar/Assets/Scripts/Pathfinding.cs at mas...

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7 Replies

Angius•7mo ago

Inetegers are value types. Meaning, they cannot be null or uninitialized. Instead, they get a default value

MODiX•7mo ago

Angius

REPL Result: Success

class Foo
{
    public int Bar;
}

new Foo().Bar

class Foo
{
    public int Bar;
}

new Foo().Bar

Result: int

Compile: 230.949ms | Execution: 21.261ms | React with ❌ to remove this embed.

Angius•7mo ago

In the case of an integer, it's 0

DarmynOP•7mo ago

ahh okay that makes a lot of sense now thanks

leowest•7mo ago

just keep in mind they are unassinged if ur inside a method for example i.e.:

public void Something()
{
    int x;
    // print x, error
    // error CS0165: Use of unassigned local variable 'x'
}

public void Something()
{
    int x;
    // print x, error
    // error CS0165: Use of unassigned local variable 'x'
}

DarmynOP•7mo ago

that's kind of weird what's the reason?

leowest•7mo ago

because the compiler in order to avoid unnecessary issues prevents local and body variables from being unassigned, These variables depend on either invocation or input to be assigned. unlike a field for a local variable the compiler doesn't assume anything

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Help understanding some code