The Whiteboard

user114359

12:12 AM

Every time I see the message "Congratulations! That was just a test, you done got it!" during a review I feel like I should win something. It really means "Congratulations! The system will let you keep reviewing stuff!"

user55340

12:32 AM

I can write a Builder that will take a series of methods like (new Builder()).one().one().build() such that it will only be possible to build if the binary number (in this case 11 (3)) is evenly divisible by 3.

user55340

1:26 AM

user55340

Umm... yea.

user114359

1:38 AM

@MichaelT ???

user55340

@Snowman Mini Metro. Was going along nicely and then all of a sudden all the stations just started pumping out riders. It went hand basket very fast.

user114359

store.steampowered.com/app/287980 ?

user55340

@Snowman store.steampowered.com/app/287980

user55340

Original flash version at dinopoloclub.com/minimetro

user114359

1:55 AM

Stupid Steam. It can never remember my browser. Every time I visit the site it has to mail me a new access code.

user55340

3:03 AM

Ok... that mod 3 thing. Got it working. Its kind of neat.

user55340

package net.shagie.typefun.main;

import net.shagie.typefun.types.numbers.Builder;

public class Main {
    public static void main(String[] args) {
        Builder num = new Builder();
        System.out.println(num.start().one().one().build());
        num = new Builder();
        System.out.println(num.start().one().zero().build());  // compile error here
    }
}

user55340

And that compile error is intentional.

user55340

package net.shagie.typefun.types.numbers;

public class Builder implements Zero, One, Two {
    int value;
    public Builder() {
        value = 0;
    }

    public Zero start() {
        return this;
    }

    public int build() {
        return value;
    }

    public Builder zero() {
        value *= 2;
        return this;
    }

    public Builder one() {
        value *= 2;
        value += 1;
        return this;
    }
}

user55340

public interface One {
    Zero one();
    Two zero();
}

user55340

public interface Two {
    One zero();
    Two one();
}

user55340

3:04 AM

public interface Zero {
    Zero zero();
    One one();
    int build();
}

user55340

The relevant state table is

user55340

user114359

What is its purpose?

user55340

3:30 AM

@Snowman to implement a simple finite state automata in the type system of a builder. It's one thing to do a tree with the type system - another to implement a DFA.

user55340

Thus, purely a proof of concept. But one that has deeper implications as to what can be done.

user55340

It means that a regular DSL can be done in the type system. But a more complex one with nesting that isn't regular can't be done without ambiguity.

user15026

@Snowman Oh that makes me crazy

user114359

@MichaelT ah, so basically to see if you can bastardize a builder pattern, not because there is an actual real-world use for it (yet).

user114359

@AshleyNunn Steam is annoying. Every time I use it, browser or app, it wants to verify my email. Seems like its app needs to be updated daily, too.

user15026

3:45 AM

The app is less panicky about things, but yeah, it does seem to need a lot of updates

user55340

3:57 AM

@Snowman it's a question of what the most powerful language you can use practically within the type system. I have had reason to use simpler ones where a call of this builder method precludes a call to that method. But that was more of a tree rather than a DFA.

user114359

@MichaelT if you can use the type system to build a DFA, you can use it to implement regular expression matching.

user55340

4:22 AM

@Snowman yep. In the type system. That's reasonablely interesting. Though it has to be a DFA implementation rather than NDFA.

user114359

@MichaelT the two are equivalent, one can be converted to the other. It just might be a bit larger as a DFA than a NDFA

user55340

4:40 AM

One interface for each state.

Robert Harvey

6:30 AM

2

Q: What happens to a character that drinks green dragon acid?

I've been DMing a Second Edition AD&D game. The fighter of the party got really upset because an NPC thief knocked him unconscious and took a potion of giant's blood off of him. He thought that the thief of the party, one of my other players stole it from him. The fighter then chose to kill the p...

Fun drinking game: Find bizarre Arqade or RPG question titles, and try to apply them to real-life scenarios.

Duga

9:17 AM

Moreover, Stack Overflow is not for "Should I?" questions. Head to programmers.stackexchange.com or codereview.stackexchange.com, depending on how you (can) formulate the question. — BalusC 41 secs ago

Duga

9:29 AM

@BalusC It might be good to point out what the different sites expect, or at least link to their help centers. I believe a lot of work needs to be done for this question to belong at either CR or Programmers. — Simon Forsberg 53 secs ago

ratchet freak

9:41 AM

@Snowman a DFA of a equivalent NDFA of size n can be 2^n

(worst case)

you can make a NFA by instead of keeping 1 state as current you keep a set of them and apply the current input against each one per step

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