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Discussion on: Don’t pay the for-loop tax

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Replies for: I think the only argument for using a a for-loop is to break out of the loop. I think pretty much everything else can be done using the functional ...

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danhomola profile image
Dan Homola •

While I agree that breaking out of a loop is a point for the loops, breaking out of a for rubs me the wrong way. I believe you should use a while (or do-while) loops and specify the condition appropriately. Breaks hamper readability imho and make the code even harder to reason about or even formally verify.

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tbodt profile image
tbodt • • Edited

I've written plenty of loops that would look a lot worse if I had to write them without break statements. For example, this code to look for possible forward moves for a white rook on a chessboard:

while (row++ < BOARD_TOP) {
    if (is_white_piece(row, column))
        break;
    GENERATE_MOVE;
    if (is_black_piece(row, column))
        break;
}
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The first check could obviously be moved into the loop condition, but I can't think of a good way to move the second check into the loop condition too.

Edit: Language is C.
Edit 2: GENERATE_MOVE call was in the wrong place, moved it outside of the second if.

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maxart2501 profile image
Massimo Artizzu •

If that's still JavaScript (could be even C or Java), it could be refactored in a more expressive way:

const piece = chessboardRows.find(pieceAtColumn(column));
if (piece && isWhite(piece)) {
    GENERATE_MOVE;
}

function pieceAtColumn(column) {
    return function(row) {
        // something like row[column]?
    };
}
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Maybe it's more verbose, but also clearer.

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tbodt profile image
tbodt •

This was C, I didn't have a find method on all the arrays.

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maxart2501 profile image
Massimo Artizzu •

Ah, crud, you're out of luck then XD

I think the aim of this article is mainly JavaScript or any other language that support methods for functional programming.

I guess you're stuck with classic loops unless some kind of abstraction helps you with that (in Java <8 it's still a mess anyway).

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tbodt profile image
tbodt •

I discovered that I pasted the code wrong, so I've edited the post to correct that. In the original version I could have written a function to find the index in the array, but I can't do that for the correct version.

 
danhomola profile image
Dan Homola •

I agree the loop would look worse. However, in this case all you are doing is finding the first piece and if it's white calling a method, right?

So you could do something like

const pieceIndex = findFirstPiece(row);
if (pieceIndex > 0 && is_white_piece(pieceIndex , column))
  GENERATE_MOVE;
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where the findFirstPiece would find the first row value that is either a white or a black piece, returning -1 if no such value was found.

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tbodt profile image
tbodt •

Oops, I pasted the code wrong. What I wanted to do was generate every move from the current position of the rook up to a piece, and including the piece if the piece is a black piece. See updated post.