Chief Delphi - Ternary operators

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Re: Ternary operators

Yeah, we do all the time. Although, prior to this year I was the only one on the team who knew about them. I distinctly remember explaining them last year, saying that they are the text equivalent of that triangle thing in LabVIEW (bleh!), though apparently no one remembered.

examples from our code:

text output:

Code:

C.lcd.lines[0]="compressor:"+(comp.getPressureSwitchValue()?"off":"on");

C.lcd.lines[1]="SideKicker: "+(C.sideKickLoaded<0?"released":"loaded");

flipping a roller based on a switch:

Code:

roller.set(C.rollerSpeed*(C.rollerForward?1:-1));

only spinning the extend-able wheels if they're extended

Code:

fDrive.set(C.upFront? C.fDrive:0);//if they're up, don't bother

bDrive.set(C.upBack ?-C.bDrive:0);//if they're up, don't bother

Re: Ternary operators

A ternary operator statement is kind of like a small switch statement. They can be useful, and if you like them go ahead and use them. But don't fall into the trap of thinking that they are necessarily more efficient. That depends on the language and compiler, and exactly how the if statement and the ternary statement are set up. Just because one piece of code is longer than another does not mean that it will be compiled into less efficient code. In a great many cases both pieces of code will compile into identical or nearly identical object code.

I would tend to argue that they almost never make code easier to understand than a well written if - else. If you know what you are doing then they may not be any more difficult to read, but I don't think the use of a ternary statement will make an unclear if - else statement suddenly clear.

Using the cRIO and Java or C++, I think the most important thing to do with the code is to make it easily readable. There is no compelling reason to have a small code size, just good efficient code. Think of how much time you spend tweaking and debugging for any program. But then place this in the context of a robotics competition where finding the problem code and fixing it must often be done in a very short, fixed period of time. Code clarity is essential. So use structures that all of the programmers agree upon ahead of time. A set of coding standards is never a bad idea. (And it will help student programmers get some real world experience.) So use the format that your team understands and wants to use.

Re: Ternary operators

Quote:

Originally Posted by mathking (Post 948867)

Using the cRIO and Java or C++, I think the most important thing to do with the code is to make it easily readable.

I agree 100%. I have heard that code is read on average ten times more often than it is written. Style is personal preference, but would you rather save some keystrokes now, or a debugging headache a month later?

Re: Ternary operators

i always have three lines of comments after ternary operators explaining them and instructions to yell at me if they dont understand.

Re: Ternary operators

I use these all the time in my computer science class at the University of Minnesota

Re: Ternary operators

Quote:

Originally Posted by Robototes2412 (Post 948102)

Was I the only one that used these on the robot?

For those not in the know, Ternary operators are essentially an inline if statment.

Example using if statements, like mama told you to do so:

Code:

boolean getState() {

    if(this.thing.state) {

        return true;

    else {

        return false;

    }

}

Example using the ternary operators:

Code:

boolean getStateTernary() {

    return this.thing.state ? true : false;

}

It does the same thing but is way easier.

The layout is:

Code:

variable = [boolean condiditon] ? [if its true] : [if its false];

This works in C, C++, Java, and I believe C#.

Did anyone else use these?

I would recommend against coding in this style as not only is it not concise, but there is an overhead to making function/method calls. Why bury a simple boolean test in a bunch of syntax? As a rule of thumb, if you can code something with fewer lines of code, it is typically better to do so.

Re: Ternary operators

Quote:

Originally Posted by Al3+ (Post 948545)

Technically this could be also written:

Code:

return isReversed ^ wpiSolenoid.get(); // if reversed, then flip solenoid value

though the ?: version is arguably more readable.

Once again, it's about clarity of intent. Make it obvious to the reader what you are doing. IMO, if you're choosing what to return conditionally, putting the conditional inside the return statement is more readable (provided, of course, the reader knows what a ternary operator is).

The XOR, on the other hand, would make even someone familiar with that operator stop and think, "now what could he possibly be doing here?"

Quote:

Originally Posted by LukeS (Post 948852)

Code:

C.lcd.lines[0]="compressor:"+(comp.getPressureSwitchValue()?"off":"on");

C.lcd.lines[1]="SideKicker: "+(C.sideKickLoaded<0?"released":"loaded");

flipping a roller based on a switch:

Code:

roller.set(C.rollerSpeed*(C.rollerForward?1:-1));

only spinning the extend-able wheels if they're extended

Code:

fDrive.set(C.upFront? C.fDrive:0);//if they're up, don't bother

bDrive.set(C.upBack ?-C.bDrive:0);//if they're up, don't bother

Try this:

Code:

C.lcd.lines[0] = "compressor:" + (comp.getPressureSwitchValue() 

        ? "off"

        : "on");

C.lcd.lines[1]= "SideKicker: " + (C.sideKickLoaded < 0 

        ? "released"

        : "loaded");

Code:

roller.set(C.rollerSpeed * (C.rollerForward

        ? 1

        : -1));

Code:

// If they're up, don't bother

fDrive.set(C.upFront

        ? C.fDrive 

        : 0);

bDrive.set(C.upBack 

        ? -C.bDrive

        : 0);

See what some well-placed white space can do for readability? Granted, breaking after ternary operators is my personal preference, but you should at the very least surround your operators with spaces. "Well-placed white space will save mistakes!" Say it with me now...:D

Re: Ternary operators

Quote:

Originally Posted by FRC4ME (Post 948969)

Oh, I know, I'm our teams white-space nazi! (if you don't believe me, just check*) I just generally feel that ternaries should be a single line, although, looking at how you did it, I like how newlines looks with text strings. However, I still feel that for the others, a single line is more readable. Looking at the drive code in black, I would probably add more spaces, but with syntax highlighting, I think it's fine how it is.

Also, for text output, the reason the compressor line has NO spaces at all is that with 2 4-character tabs (class and method) we were squeezing for 80 columns (something which I am also a nazi for).

* although, it does look like some spacing got messed up when tweaking numbers in autonomous. I'll fix this and update it today or tomorrow. (that URL is always the newest version)