[–] 3 points 5 days ago

FYI for anyone who depended on old reddit: There are a lot of Redlib instances out there that are being actively updated to the latest instance with fairly high uptime. I use an add-on called LibRedirect which redirects any links from reddit to one of these instances. If Reddit ever hunts down these instances, you can host your own.

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  • [–] 3 points 3 weeks ago* (1 child)

    Stack doesn't actually allow indexing, and ElementAt is an extension method implemented by accessing Stack's iterator. My honest recommendation is to not use Stack, even if that's what the book was using. Stacks are not really meant to be traversed. They're meant to be pushed to, and popped (or peeked) from. Each ElementAt call requires O(N) time to retrieve. I recommend switching to List and implementing 'push', 'pop', and 'peek' as such:

    // Instead of Push
    scopes.Add(item);
    
    // Instead of Peek
    int peeked = scopes[^1];
    
    // Instead of Pop
    int popped = scopes[^1];
    scopes.RemoveAt(scopes.Count - 1);
    

    However, I understand that is a bit of a change. If you'd prefer to keep it as a stack, a simple reversal of the for loop can get the job done.

    	// Resolve local variable assignment
    	private void ResolveLocal(Expr expr, Token name) {
    		// Decrement through scopes
    		for (int i = 0; i < scopes.Count; i++) {
    			// Pass amount of layers since declaration to interpreter
    			if (scopes.ElementAt(i).ContainsKey(name.getLexeme())) {
    				interpreter.Resolve(expr, i);
    				return;
    			}
    		}
    	}
    

    That's enough to get these scripts running.

    >for(var i = 0; i < 10; i = i + 1) { print i;} 
    0
    1
    2
    3
    4
    5
    6
    7
    8
    9
    
    >var a = 0; var temp; for(var b= 1; a < 10000; b = temp + b) { print a; temp = a; a = b;}
    0
    1
    1
    2
    3
    5
    8
    13
    21
    34
    55
    89
    144
    233
    377
    610
    987
    1597
    2584
    4181
    6765
    

    By the way, I noticed that redefining a global variable will crash as well, but a scoped variable will display an error as intended.

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  • [–] 5 points 3 weeks ago* (3 children)

    Hard bug to spot for sure. It's due to a difference between C# and Java. C#'s Stack.ElementAt() is not the same thing as Java's Stack.elementAt()/Stack.get(). They're actually reversed. Also, ElementAt is a Linq extension method and not a default method like in Java. See the below code/output:

    import java.util.Stack;
    Stack<Integer> stack = new Stack<Integer>();
    stack.push(1);
    stack.push(2);
    stack.push(3);
    System.out.println(stack.elementAt(0));
    

    Output: 1

    using System;
    using System.Collections.Generic;
    using System.Linq;
    
    Stack<int> stack = new();
    stack.Push(1);
    stack.Push(2);
    stack.Push(3);
    Console.WriteLine(stack.ElementAt(0));
    

    Output: 3

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