20 Collapsing Haskell code

This is hs-minor-mode for haskell-mode. This module uses hideshow module.

To activate this minor mode (haskell-collapse-mode)

• M-x haskell-collapse-mode is "To start haskell-collapse-mode".

This minor mode works with indentation.

In a quick glance:

C-c  C-c

is bound to haskell-hide-toggle

C-c  C-M-c

C-c  C-M-h

C-c  C-M-s

are all bound to haskell-hide-toggle-all

How to use M-x haskell-hide-toggle?

Place your point on the code block that you want to collapse and hit the keybinding. Now the code collapses and you can see the first line of the block and elipsis.

Take this example code (example usage of M-x haskell-hide-toggle): when you place the cursor here, like this (notice the thick block in the first line):

f█x | rem i 3 == 0 = if i == 0 && (k /= 0) then (c k) else (h j) | otherwise = 0 where i = sum x j = g x (div i 3) 0 0 [] k = zeroes x 0

or

f x | rem i 3 == 0 = if i == 0 && (k /= 0) then (c k) else (h j) █ | otherwise = 0 where i = sum x j = g x (div i 3) 0 0 [] k = zeroes x 0

then when you collapse it becomes something like this:

f█x…

It works in terms of (indentation) blocks.

One more example:

f x | rem i 3 == 0 = if i == 0 && (k /= 0) then (c k) else (h j) | otherwise = 0 w█ere i = sum x j = g x (div i 3) 0 0 [] k = zeroes x 0

or

f x | rem i 3 == 0 = if i == 0 && (k /= 0) then (c k) else (h j) | otherwise = 0 where i = sum x j = g x (div i 3) 0 0 [] █ k = zeroes x 0

this, will result in something like:

f x | rem i 3 == 0 = if i == 0 && (k /= 0) then (c k) else (h j) | otherwise = 0 where i = sum █…

The other functionality M-x haskell-hide-toggle-all also works only for indentation and it collapses all toplevel functions.

So a file that looks like this:

main = interact $ show.f. map read .words
f (x:xs) = dp x xs

dp money a | money < 0 || null a = [1..1000]
dp 0 a = []
dp money a @ (coin:coins)
  | (length i) <= length j = i
  | otherwise = j
  where i = (coin:(dp (money-coin) a))
        j = (dp money coins)

will turn into this:

main = interact $ show.f. map read .words
f (x:xs) = dp x xs

dp money a | money < 0 || null a = [1..1000]
dp 0 a = []
dp money a @ (coin:coins)…