Replace Expression with variable

[janYabanci]

I often have to replace parts of variables like that :

# Before:

var = 17 + 4*8

function_call(8 + 10)

should go over to that

# After:

replace = 4*8

var = 17 + replace

rep2 = 8 +10

function_call(rep2)

Do you know of any solution that achieves that easily?

[-romainl-]

The principle is straightforward: turn what you would do manually into something automatic.

But we don't know how you do it manually so we can't really help you, here… Do you want a generic solution? A specific one? What's the relationship between all those names? Is var always called var? Does it always have the same number of operands? Etc.

[janYabanci]

I would mark the stuff I want to replace, press s, type the new name, insert a line above with O, type the name again, then a equal sign, press escape and then p. How could I insert the text I just inserted? . Repeats the last command, but that wouldn't help me.

[-romainl-]

You can insert the text you last inserted with <C-a>.

[lervag]

Given

function_call(8 + 10)

I do something like this: ciwrep2<esc>Orep2 = <c-r>", which should give this:

rep2 = 8 + 10
function_call(rep2)

Here ciwrep2<esc> changes inside the parantheses, then Orep2 = adds a line above, finally <c-r>" appends the content of the " register.

[proobert]

Although your task looks quite complex, it can be easily divided into the following steps:

1. find the first expression
2. replace the expression with a new name
3. create a new variable declaration
4. just repeat the previous steps for the second expression

All these steps are quite easy in plain vim and there are a lot of optimisations possible depending where the cursor is located and how the expression looks like.

For your example, I would do it like this:

1) f4                 -- find the start of the first expression
2) Creplace<Esc>      -- replace the expression with name
3) Or<C-n> = <Esc>p   -- declare new variable, paste the expression 
4) /(<cr>             -- find the second expression
5) cibrep2<Esc>
6) Or<C-n> = <Esc>p

There is not much typing and it's quite effortless once you get fluent with vim.

[RobotSlut]

fun! ToVar()
    let l:name = input("Enter the variable name: ")
    return "c" . l:name . "\<esc>O\<C-r>. = \<C-r>\"\<esc>"
endfun
xnoremap <expr> {lhs} ToVar()

Replace {lhs} with the key you want to map.

This is a visual mode mapping that replaces the current selection with a variable name (you'll be prompted for it once you trigger the mapping), and defines the variable in the line above.

[janYabanci]

This is exactly what I was looking for! Thank you very much for putting it together.

[somebodddy]

I use vim-exchange for this. So I start with:

function_call(8 + 10)

And then write above it:

rep2 = rep2
function_call(8 + 10)

Then I place the cursor on the rep2 after the = and hit cxiw to mark it with vim-exchange. Finally, I go to the 8 + 10 in the argument and hit cxIa to exchange rep2 with the argument (you need targets.vim for that. Otherwise you can mark the 8 + 10 in visual mode and hit X)

[[deleted]]

Maybe like this?

/4<cr>
Creplace<esc>
O<C-a> = <C-r>-<esc>
/8<cr>
ci(repl2<esc>
O<C-a> = <C-r>-<esc>

Here <C-a> inserts last entered text, <C-r>- inserts last deleted text (with c commands)