Java and Float comparisons

[mittelmark]

Java seems to have trouble with comparing floats, so instead of doing things like:

f1 > f2

in Java we should do:

Float.compare(f1,f2)>0

Should this again go in a native block? Or are there any other workarounds?

like f1-f2>0.00001 ... ?

9 Languages ... Welcome to Babylon.

[pfusik]

What do you mean?

C:\0\ci>cat Test245.java
public class Test245
{
        public boolean cmp(float a, float b)
        {
                return a > b;
        }
}

C:\0\ci>javac Test245.java

C:\0\ci>javac --version
javac 25.0.3

[mittelmark]

I have javac 21.0.11 here on Fedora Linux. For now I use:

				if ((x[i]-x[j])>0.0001) {
					rnk=rnk+1;
				} else if (Math.Abs(x[i]-x[j])<0.0001) { // they are (almost) the same
					same = same + 1.0;
				}

which is sufficient for our needs for now ... Probably I should add a few zeros.

[pfusik]

I don't understand what you mean by "Java seems to have trouble with comparing floats". Can you show a reproducer? Is there an error message?

[mittelmark]

Sorry, for the misunderstanding. No, nothing on Fusions side. I just create a set of floats and some of them should have the same value. Let's give that example:

public static class Test6 {
	public static void Main(string[] args) {
		List<float>() x;
		x.Add(2.0);
		x.Add(2.0);
		if (x[0] == x[1]) {
			Console.WriteLine($"x0 and x1 are equal!");
		} else {
			Console.WriteLine($"x0 and x1 are not equal!");
		}
	}
}

C, C#, C++, D, Js, Ts, Python, Swift x[1] and x[2] are equal. But not in Java. See below.

$ make FUFILES=Test6.fu APP=Test6 c
[ -d cm ] || mkdir cm
fut -D TESTMAIN Test6.fu -o cm/test6.c
gcc cm/test6.c `pkg-config --cflags --libs glib-2.0` -o cm/test6-c -lm
./cm/test6-c
x0 and x1 are equal!
$ make FUFILES=Test6.fu APP=Test6 cpp
[ -d cppm ] || mkdir cppm
fut -D TESTMAIN Test6.fu -o cppm/test6.cpp
g++ -std=c++20 cppm/test6.cpp -o cppm/test6-cpp
./cppm/test6-cpp | tail -n 20
x0 and x1 are equal!
$ make FUFILES=Test6.fu APP=Test6 cs
[ -d MainApp ] && rm -rf MainApp
dotnet new console -n MainApp --no-restore --force
Die Vorlage "Konsolen-App" wurde erfolgreich erstellt.

rm MainApp/Program.cs
fut -D TESTMAIN Test6.fu -o MainApp/test6.cs
cd MainApp && dotnet build -c Release
Wiederherstellung abgeschlossen (0,7s)
  MainApp net10.0 Erfolgreich (0,6s) → bin/Release/net10.0/MainApp.dll

Erstellen von Erfolgreich in 2,0s
./MainApp/bin/Release/net10.0/MainApp
x0 and x1 are equal!
$ make FUFILES=Test6.fu APP=Test6 d
[ -d dm ] || mkdir dm
fut -D TESTMAIN Test6.fu -o dm/test6.d 
dmd dm/test6.d -of=dm/test6-d 
./dm/test6-d
x0 and x1 are equal!
$ make FUFILES=Test6.fu APP=Test6 java
[ -d javam ] || mkdir javam
fut -D TESTMAIN Test6.fu -o javam/Test6.java 
javac javam/*.java
java -cp ./javam Test6
x0 and x1 are not equal!
$ make FUFILES=Test6.fu APP=Test6 js
[ -d jsm ] || mkdir jsm
fut -D TESTMAIN Test6.fu -o jsm/test6.js
node jsm/test6.js
x0 and x1 are equal!
$ make FUFILES=Test6.fu APP=Test6 ts
[ -d tsm ] || mkdir tsm
fut -D TESTMAIN Test6.fu -o tsm/test6.ts
bun tsm/test6.ts
x0 and x1 are equal!
$ make FUFILES=Test6.fu APP=Test6 py
[ -d pym ] || mkdir pym
fut -D TESTMAIN Test6.fu -o pym/test6.py
python3 pym/test6.py
x0 and x1 are equal!
$ make FUFILES=Test6.fu APP=Test6 swift
[ -d swiftm/Sources/swift ] || mkdir -p swiftm/Sources/swift
fut -D TESTMAIN Test6.fu -o swiftm/Sources/swift/swift.swift
cd swiftm && swift build
[1/1] Planning build
Building for debugging...
[8/8] Linking swift
Build complete! (0.63s)
cd swiftm && swift run
Building for debugging...
[1/1] Write swift-version-639EA65116052DDC.txt
Build of product 'swift' complete! (0.11s)
x0 and x1 are equal!
./swiftm/.build/x86_64-unknown-linux-gnu/debug/swift
x0 and x1 are equal!

That's why I needed a workaround. Its not fusions fault, just Java's.

[mittelmark]

That lead to a serious bug in the rank and in the randomize functions of our Stats.fu file and my students dropped out Java, I'll try now to reinduced it.

[pfusik]

This is a bug in fut, affecting == and != comparisons of List<number> elements on both sides. A workaround is to add + 0 on one of the sides of comparison.
Other comparisons (< <= > >=) don't seem to be affected.
I'm working on a fix.

[pfusik]

Fixed now. Pity the Java compiler doesn't even warn - this must be a common pitfall.

[mittelmark]

Yeah works:

 make FUFILES=Test6.fu APP=Test6 java
[ -d javam ] || mkdir javam
fut -D TESTMAIN Test6.fu -o javam/Test6.java 
javac javam/*.java
java -cp ./javam Test6
x0 and x1 are equal!