Mathematica editor: Removing the right matching ']' automatically when the left '[' is removed?

问题

In Mathematica editor (i.e. notebook), one of the hardest things I always found is when I want to edit some long expression, and go and remove the left end "[" of some expression then before I get the chance to remove the right "]", the code in the cell will get all messed up, since it is no longer balanced, making it really hard to go chase the, now hanging, right end "]" since it is no longer in its original place!

Here is a simple example, suppose we have this

Text[Row[{PaddedForm[currentTime, {6, 3}, NumberSigns -> {"", ""}, NumberPadding -> {"0", "0"}]}]]

now say I wanted to remove the outside Text[] call. So I delete "Text[" and before I get a chance to delete the other side "]", the notebook will now juggle things all over the place, making it hard to find the right "]". For long cell (which is the case for demonestrations work), the code can shift by large amount, and the right "]" can go out of view as well, has to scroll down and up looking for it.

Is there a way to set it, via an option or such, so that when I delete the left "[", Mathematica will automatically delete the matching right "]"? This applies for "(" and ")" as well.

This is really a big problem with the use of the notebook editor for me. Can't tell you how much time I spend just looking the hanging "]".

thanks --Nasser

回答1:

The following will add the keyboard shortcut Shift+Backspace to remove the closest enclosing brackets of the current cursor position. It also adds a menu item to the edit menu.

This function takes the current clipboard content and removes the first and last "word".

cutClipboardBrackets:=Module[{nb},
 nb=CreateDocument[{},Visible->False,WindowSelected->False];
 NotebookWrite[nb,NotebookGet@ClipboardNotebook[]]
 SelectionMove[nb,All,CellContents];
 FrontEndExecute[FrontEndToken[nb,"MoveCellBeginning"]]          
 SelectionMove[nb,All,Word,1];
 NotebookDelete[nb];
 FrontEndExecute[FrontEndToken[nb,"MoveCellEnd"]];
 SelectionMove[nb,All,Word,1];
 NotebookDelete[nb];
 SelectionMove[nb,All,CellContents];
 FrontEndExecute[FrontEndToken[nb,"Copy"]];
];

This can be used to remove brackets, since they are the first and last word when copying FrontEndExecute[FrontEndToken[nb,"Balance"]]. The function that selects, cuts, removes the additional brackets and pastes is:

RemoveBrackets[nb_]:= ( 
 FrontEndExecute[FrontEndToken[nb,"Balance"]];
 FrontEndExecute[FrontEndToken[nb,"Cut"]];
 cutClipboardBrackets;
 FrontEndExecute[FrontEndToken[nb,"Paste"]];
);

Finally we can protect the functions and add a keyboard shortcut (like here):

 Protect[cutClipboardBrackets,ClipboardBrackets];

 FrontEndExecute[
  FrontEnd`AddMenuCommands[
   "SelectAll",{Delimiter,MenuItem["Delete Outer Brackets",
     FrontEnd`KernelExecute[nb=CreateDocument[Null,Visible->False,WindowSelected->True];
  NotebookWrite[nb,Cell[BoxData[RowBox[{"RemoveBrackets[SelectedNotebook[]]"}]],"Input"]];
  SelectionMove[nb,Previous,Cell];
  SelectionEvaluate[nb];
  NotebookClose[nb]],
  MenuKey["Backspace",Modifiers->{"Shift"}],System`MenuEvaluator->Automatic]}]]

回答2:

I shall think about an automatic method, but I currently handle this with:

place the cursor on the first token inside the function you want to delete (in this case Row)
press Ctrl+. until everything inside is selected (twice, in this case)
Copy
press Ctrl+. once to include the function to delete in the selection
Paste

It is really quite fast once you do it a few times.

Andrew Moylan suggests this mouse variation:

Here is the variant I use for this common operation:

Triple-click "Row", Ctrl+C, Triple-click "Text", Ctrl+V, done

回答3:

If you are deleting a function with only one argument, you can

delete the function name
use (Ctrl + ., Ctrl + .) on the inside function to select its extents
go to the end of that extent and delete the ]

This website also has more information about balancing brackets in Mathematica: http://reference.wolfram.com/mathematica/howto/BalanceBracketsAndBraces.html

(If you are deleting a function with more than one argument, auto balancing probably doesn't help anyway since you still have to chase the extra arguments.)

回答4:

I don't know how to do it automatically, but here's a suggestion that can help you keep track of the brackets/parentheses visually and aid you in deleting them manually.

Break up your code into multiple lines, so that each function block opens and closes on a separate line (kinda like C, C++). For e.g., your above code will look like

Text[
 Row[{
   PaddedForm[
    currentTime, {6, 3},
    NumberSigns -> {"", ""},
    NumberPadding -> {"0", "0"}
    ]
   }]
 ]

I use this in blocks of code that are longer than a line or so, and especially in plotting, where it's real easy to keep track of the options you supply.

回答5:

I am answering my own question here. Using CODE as cell type instead of INPUT solved this issue for me. closing.

来源：https://stackoverflow.com/questions/6137716/mathematica-editor-removing-the-right-matching-automatically-when-the-left

标签

wolfram-mathematica