Doing math calculation in VIM

In vim, there is a register called = which can be used to evaluate an expression. In this post, I will show you how to select an expression and calculate the result and insert the result in VIM.

Consider you have the following expression in your VIM editor:

Q: We have 3 apples and 4 oranges, how many fruits do we have in total?
A: 3 + 4 = 
          ^ cursor here

You can use the following steps to calculate the result and insert it after the =:

1. Make sure you are in insert mode by pressing a.
2. Press ctrl + r followed by = to use the expression register.
3. Now type the expression 3 + 4 and press Enter.
4. The result 7 will be inserted after the =.
5. Press Esc to exit insert mode.

After the above steps, the text will become:

Q: We have 3 apples and 4 oranges, how many fruits do we have in total?
A: 3 + 4 = 7
           ^ cursor here

But wait, what if you have a long expression that you want to calculate, you don't want to type the whole expression again! You can use the registers to store the expression and use it later in command mode. Consider you have the following expression:

I have a long expression, 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 
                                                          ^ cursor here

You can use the following steps to calculate the result and insert it after the =:

1. Type F3 to go to the beginning of the expression.
2. Type yt= to yank till the =.
3. Now press A to go to the end of the line and enter insert mode.
4. Press ctrl + r followed by = to use the expression register.
5. Press ctrl + r followed by " to paste the yanked text.
6. Press Enter to calculate the result and insert it at the cursor position.
7. Press Esc to exit insert mode.

After the above steps, the text will become:

I have a long expression, 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 52
                                                            ^ cursor here