When I write mathematical notes using LaTeX in Neovim, LuaSnip is very helpful. However, there's no way I can implement snippets that build different tables (tables, tabulars, arrays, etc). What snippets can I use?
I know about this plugin (https://github.com/evesdropper/luasnip-latex-snippets.nvim), but I want to use my own snippets.
There's a well documented example in the LuaSnip wiki that shows how to make a snippet that can create LaTeX tables and adjust the number of rows on-the-fly (scroll to the bottom of the page to see it in action).
This offers a great starting point to then use for arrays, matrices et cetera. However, it is one of the more complex snippets that I wouldn't recommend starting with unless you've experimented with LuaSnip's various nodes, especially function nodes and dynamic nodes, and are comfortable with how they work.
I'll reproduce the example here to avoid issues with potential dead links in future. All credit to the author of LuaSnip (L3MON4D3) for the following.
Write a function that runs some other function whose output will be used in the dynamicNode-function; and updates the dynamic node.
local ls = require("luasnip")
local util = require("luasnip.util.util")
local node_util = require("luasnip.nodes.util")
local function find_dynamic_node(node)
-- the dynamicNode-key is set on snippets generated by a dynamicNode only (its'
-- actual use is to refer to the dynamicNode that generated the snippet).
while not node.dynamicNode do
node = node.parent
end
return node.dynamicNode
end
local external_update_id = 0
-- func_indx to update the dynamicNode with different functions.
function dynamic_node_external_update(func_indx)
-- most of this function is about restoring the cursor to the correct
-- position+mode, the important part are the few lines from
-- `dynamic_node.snip:store()`.
-- find current node and the innermost dynamicNode it is inside.
local current_node = ls.session.current_nodes[vim.api.nvim_get_current_buf()]
local dynamic_node = find_dynamic_node(current_node)
-- to identify current node in new snippet, if it is available.
external_update_id = external_update_id + 1
current_node.external_update_id = external_update_id
-- store which mode we're in to restore later.
local insert_pre_call = vim.fn.mode() == "i"
-- is byte-indexed! Doesn't matter here, but important to be aware of.
local cursor_pos_pre_relative = util.pos_sub(
util.get_cursor_0ind(),
current_node.mark:pos_begin_raw()
)
-- leave current generated snippet.
node_util.leave_nodes_between(dynamic_node.snip, current_node)
-- call update-function.
local func = dynamic_node.user_args[func_indx]
if func then
-- the same snippet passed to the dynamicNode-function. Any output from func
-- should be stored in it under some unused key.
func(dynamic_node.parent.snippet)
end
-- last_args is used to store the last args that were used to generate the
-- snippet. If this function is called, these will most probably not have
-- changed, so they are set to nil, which will force an update.
dynamic_node.last_args = nil
dynamic_node:update()
-- everything below here isn't strictly necessary, but it's pretty nice to have.
-- try to find the node we marked earlier.
local target_node = dynamic_node:find_node(function(test_node)
return test_node.external_update_id == external_update_id
end)
if target_node then
-- the node that the cursor was in when changeChoice was called exists
-- in the active choice! Enter it and all nodes between it and this choiceNode,
-- then set the cursor.
node_util.enter_nodes_between(dynamic_node, target_node)
if insert_pre_call then
util.set_cursor_0ind(
util.pos_add(
target_node.mark:pos_begin_raw(),
cursor_pos_pre_relative
)
)
else
node_util.select_node(target_node)
end
-- set the new current node correctly.
ls.session.current_nodes[vim.api.nvim_get_current_buf()] = target_node
else
-- the marked node wasn't found, just jump into the new snippet noremally.
ls.session.current_nodes[vim.api.nvim_get_current_buf()] = dynamic_node.snip:jump_into(1)
end
end
Bind the function to some key.
vim.api.nvim_set_keymap('i', "<C-t>", '<cmd>lua _G.dynamic_node_external_update(1)<Cr>', {noremap = true})
vim.api.nvim_set_keymap('s', "<C-t>", '<cmd>lua _G.dynamic_node_external_update(1)<Cr>', {noremap = true})
vim.api.nvim_set_keymap('i', "<C-g>", '<cmd>lua _G.dynamic_node_external_update(2)<Cr>', {noremap = true})
vim.api.nvim_set_keymap('s', "<C-g>", '<cmd>lua _G.dynamic_node_external_update(2)<Cr>', {noremap = true})
It may be useful to bind even more numbers (3-???), but two suffice for this example. Now it's time to make use of the new function.
local function column_count_from_string(descr)
-- this won't work for all cases, but it's simple to improve
-- (feel free to do so! :D )
return #(descr:gsub("[^clm]", ""))
end
-- function for the dynamicNode.
local tab = function(args, snip)
local cols = column_count_from_string(args[1][1])
-- snip.rows will not be set by default, so handle that case.
-- it's also the value set by the functions called from dynamic_node_external_update().
if not snip.rows then
snip.rows = 1
end
local nodes = {}
-- keep track of which insert-index we're at.
local ins_indx = 1
for j = 1, snip.rows do
-- use restoreNode to not lose content when updating.
table.insert(nodes, r(ins_indx, tostring(j).."x1", i(1)))
ins_indx = ins_indx+1
for k = 2, cols do
table.insert(nodes, t" & ")
table.insert(nodes, r(ins_indx, tostring(j).."x"..tostring(k), i(1)))
ins_indx = ins_indx+1
end
table.insert(nodes, t{"\\\\", ""})
end
-- fix last node.
nodes[#nodes] = t""
return sn(nil, nodes)
end
s("tab", fmt([[
\begin{{tabular}}{{{}}}
{}
\end{{tabular}}
]], {i(1, "c"), d(2, tab, {1}, {
user_args = {
-- Pass the functions used to manually update the dynamicNode as user args.
-- The n-th of these functions will be called by dynamic_node_external_update(n).
-- These functions are pretty simple, there's probably some cool stuff one could do
-- with `ui.input`
function(snip) snip.rows = snip.rows + 1 end,
-- don't drop below one.
function(snip) snip.rows = math.max(snip.rows - 1, 1) end
}
} )}))