When does a func() become too large?

This is a discussion on When does a func() become too large? within the C++ Programming forums, part of the General Programming Boards category; I have a function that performs a lot of floating-point arithmetic. The function basically calculates coordinates on a fractal-type design ...

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    When does a func() become too large?

    I have a function that performs a lot of floating-point arithmetic. The function basically calculates coordinates on a fractal-type design of sorts. The function is called 3^n times where n is the number of iterations (consequently, the overall complexity of the fractal).

    Now I understand the merits of modularizing things as a programmer, but my question is, at what point should the function be split into smaller functions, if the number of calculations within the function as it is will never change?
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    CSharpener vart's Avatar
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    When it is bigger than one screen in hight
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    Quote Originally Posted by vart View Post
    When it is bigger than one screen in hight
    Ha, is that the rule of thumb? I was kind of hoping for a more insightful answer than that.
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    CSharpener vart's Avatar
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    Quote Originally Posted by dudeomanodude View Post
    Ha, is that the rule of thumb? I was kind of hoping for a more insightful answer than that.
    Then you should go and find yourself some good coding standard manual. And read it n the topic
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    Cat without Hat CornedBee's Avatar
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    But you won't find much more than this rule of thumb. A function should be so large that it can still be easily understood, but how easily a function is understand depends heavily on what it contains.
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    (?<!re)tired Mario F.'s Avatar
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    I would also probably add the fact that a function shouldn't add functionality beyond that of which it was created for... (or some other form of this sentence. I'm sure there is a better way of saying it)
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
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    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

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    C++ Witch laserlight's Avatar
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    I would also probably add the fact that a function shouldn't add functionality beyond that of which it was created for... (or some other form of this sentence. I'm sure there is a better way of saying it)
    A function should do one thing and do it well.
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    well like I said, it performs a lot floating-point arithmetic, it contains no loops, no if-else statements, it's just a procedural calculating function, that's it. I think it's easy enough to follow, especially since there are no control structures. Also, no calculations are repeated.
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    C++ Witch laserlight's Avatar
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    Well, you should consider: are there portions of this function that can be better expressed (and maybe reused) as a unit by moving them out to another function?
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    Quote Originally Posted by laserlight View Post
    Well, you should consider: are there portions of this function that can be better expressed (and maybe reused) as a unit by moving them out to another function?
    OK, as a for instance, my function uses the distance formula, but only once. You might say that the distance function is a rather robust calculation. Is it robust enough to stick it in its own function, though?
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    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by dudeomanodude View Post
    OK, as a for instance, my function uses the distance formula, but only once. You might say that the distance function is a rather robust calculation. Is it robust enough to stick it in its own function, though?
    The advantage of putting it in its own function is that it can also be used elsewhere; do you need the distance formula elsewhere in your program? Do you need the distance formula elsewhere in some other program (written or yet unwritten)? Probably, yes; so it might not be a bad idea to have it in an easily movable state. (People tend to end up with files of functions like this that they can import as necessary.)

    Another advantage is that the code becomes self-commenting: when you see
    Code:
    d = distance(point_1, point_2);
    it's pretty obvious what's going on, more so than the actual calculation itself would be.

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    Well, if you have a piece of code in the function that you think can be used independently, then cut it out. I think the distance function could be cut out (even if you don't use it in this specific program, you'll have it ready for others).
    I might not be a pro, but I'm usually right

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    Hey thank you guys, I realize the subject of this thread may boil down to personal preference, and might also rely on a situational basis, but I think I might make better decisions now on how to modularize things.

    Always good to get the consensus of the experts here!
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    Seeing as the compilers nowadays are pretty darn good at figuring out if something should be inlined or not [and even without an inline keyword], there's really no reason to NOT split things into simpler functions if there's any scope to do that.

    A long set of calculations, with or without conditoons and such, will be clearer if each SMALL part of that calculation is separated out into smaller functions.

    If you find later that this is REALLY time-critical calculations, and could do with optimizing, then you may consider re-writing the function in a more optimal way [assuming there is such a thing].

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    Quote Originally Posted by matsp View Post
    If you find later that this is REALLY time-critical calculations, and could do with optimizing, then you may consider re-writing the function in a more optimal way [assuming there is such a thing].

    --
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    Funny you should say that, this is actually a school assignment, with the point being that after so many iterations, the computer can no longer efficiently handle the task. Right now I'm just trying to get it to work, but once that's done, I'm gonna have to go through and start counting operations to optimize the procedure.
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