@ -139,58 +139,49 @@ What's this? A fold within a fold?
Nested folds are valid. The text "Two" and "Two again" have fold level of one. The text "Three" and "Three again" have fold level of two. If you have a foldable text with a higher fold level within a foldable text, you will have multiple fold layers.
## Marker Fold
To use a marker fold, run:
## Expression Fold
```
:set foldmethod=marker
```
Expression fold allows you to define an expression to match for a fold. After you define the fold expressions, Vim scans each line for the value of `'foldexpr'`. This is the variable that you have to configure to return the appropriate value. If the `'foldexpr'` returns 0, then the line is not folded. If it returns 1, then that line has a fold level of 1. If it returns 2, then that line has a fold level of 2. There are more values other than integers, but I won't go over them. If you are curious, check out `:h fold-expr`.
Suppose you have the text:
First, let's change the foldmethod:
```
Hello
{{{
world
vim
}}}
:set foldmethod=expr
```
Run `zM`, you will see:
Suppose you have a list of breakfast foods and you want to fold all breakfast items starting with "p":
```
hello
+-- 4 lines: -----
donut
pancake
pop-tarts
protein bar
salmon
scrambled eggs
```
Vim sees `{{{` and `}}}` as fold indicators and folds the texts between them. With the marker fold, Vim looks for special markers, defined by `'foldmarker'` option, to mark folding areas. To see what markers Vim uses, run:
Next, change the `foldexpr` to capture the expressions starting with "p":
```
:set foldmarker?
:set foldexpr=getline(v:lnum)[0]==\\"p\\"
```
By default, Vim uses `{{{` and `}}}` as indicators. If you want to change the indicator to another texts, like "coffee1" and "coffee2":
```
:set foldmarker=coffee1,coffee2
```
The expression above looks complicated. Let's break it down:
- `:set foldexpr` sets up the `'foldexpr'` option to accept a custom expression.
- `getline()` is a Vimscript function that returns the content of any given line. If you run `:echo getline(5)`, it will return the content of line 5.
- `v:lnum` is Vim's special variable for the `'foldexpr'` expression. Vim scans each line and at that moment stores each line's number in `v:lnum` variable. On line 5, `v:lnum` has value of 5. On line 10, `v:lnum` has value of 10.
- `[0]` in the context of `getline(v:lnum)[0]` is the first character of each line. When Vim scans a line, `getline(v:lnum)` returns the content of each line. `getline(v:lnum)[0]` returns the first character of each line. On the first line of our list, "donut", `getline(v:lnum)[0]` returns "d". On the second line of our list, "pancake", `getline(v:lnum)[0]` returns "p".
- `==\\"p\\"` is the second half of the equality expression. It checks if the expression you just evaluated is equal to "p". If it is true, it returns 1. If it is false, it returns 0. In Vim, 1 is truthy and 0 is falsy. So on the lines that start with an "p", it returns 1. Recall if a `'foldexpr'` has a value of 1, then it has a fold level of 1.
If you have the text:
After running this expression, you should see:
```
hello
coffee1
world
vim
coffee2
donut
+-- 3 lines: pancake -----
salmon
scrambled eggs
```
Now Vim uses `coffee1` and `coffee2` as the new folding markers. As a side note, an indicator must be a literal string and cannot be a regex.
## Syntax Fold
Syntax fold is determined by syntax language highlighting. If you use a language syntax plugin like [vim-polyglot](https://github.com/sheerun/vim-polyglot), the syntax fold will work right out of the box. Just change the fold method to syntax:
@ -218,49 +209,6 @@ syntax region jsBracket matchgroup=jsBrackets s
This guide won't cover the `syntax` feature. If you're curious, check out `:h syntax.txt`.
## Expression Fold
Expression fold allows you to define an expression to match for a fold. After you define the fold expressions, Vim scans each line for the value of `'foldexpr'`. This is the variable that you have to configure to return the appropriate value. If the `'foldexpr'` returns 0, then the line is not folded. If it returns 1, then that line has a fold level of 1. If it returns 2, then that line has a fold level of 2. There are more values other than integers, but I won't go over them. If you are curious, check out `:h fold-expr`.
First, let's change the foldmethod:
```
:set foldmethod=expr
```
Suppose you have a list of breakfast foods and you want to fold all breakfast items starting with "p":
```
donut
pancake
pop-tarts
protein bar
salmon
scrambled eggs
```
Next, change the `foldexpr` to capture the expressions starting with "p":
```
:set foldexpr=getline(v:lnum)[0]==\\"p\\"
```
The expression above looks complicated. Let's break it down:
- `:set foldexpr` sets up the `'foldexpr'` option to accept a custom expression.
- `getline()` is a Vimscript function that returns the content of any given line. If you run `:echo getline(5)`, it will return the content of line 5.
- `v:lnum` is Vim's special variable for the `'foldexpr'` expression. Vim scans each line and at that moment stores each line's number in `v:lnum` variable. On line 5, `v:lnum` has value of 5. On line 10, `v:lnum` has value of 10.
- `[0]` in the context of `getline(v:lnum)[0]` is the first character of each line. When Vim scans a line, `getline(v:lnum)` returns the content of each line. `getline(v:lnum)[0]` returns the first character of each line. On the first line of our list, "donut", `getline(v:lnum)[0]` returns "d". On the second line of our list, "pancake", `getline(v:lnum)[0]` returns "p".
- `==\\"p\\"` is the second half of the equality expression. It checks if the expression you just evaluated is equal to "p". If it is true, it returns 1. If it is false, it returns 0. In Vim, 1 is truthy and 0 is falsy. So on the lines that start with an "p", it returns 1. Recall if a `'foldexpr'` has a value of 1, then it has a fold level of 1.
After running this expression, you should see:
```
donut
+-- 3 lines: pancake -----
salmon
scrambled eggs
```
## Diff Fold
Vim can do a diff procedure to compare two or more files.
@ -310,6 +258,58 @@ vim is awesome
Vim automatically folds some of the identical lines. When you are running the `vimdiff` command, Vim automatically uses `foldmethod=diff`. If you run `:set foldmethod?`, it will return `diff`.
## Marker Fold
To use a marker fold, run:
```
:set foldmethod=marker
```
Suppose you have the text:
```
Hello
{{{
world
vim
}}}
```
Run `zM`, you will see:
```
hello
+-- 4 lines: -----
```
Vim sees `{{{` and `}}}` as fold indicators and folds the texts between them. With the marker fold, Vim looks for special markers, defined by `'foldmarker'` option, to mark folding areas. To see what markers Vim uses, run:
```
:set foldmarker?
```
By default, Vim uses `{{{` and `}}}` as indicators. If you want to change the indicator to another texts, like "coffee1" and "coffee2":
```
:set foldmarker=coffee1,coffee2
```
If you have the text:
```
hello
coffee1
world
vim
coffee2
```
Now Vim uses `coffee1` and `coffee2` as the new folding markers. As a side note, an indicator must be a literal string and cannot be a regex.
## Persisting Fold
You loses all fold information when you close the Vim session. If you have this file, `count.txt`:
Victorhck
3 years ago