How to prepend an item to Lua array?

user_5290519 0
Viewed 136

As title. I'm working with a neovim config, and the content of this array will be concatenated into a command to execute:

cmd = { 'mono', omnisharp_bin, '--languageserver', '--hostPID', tostring(vim.fn.getpid()) }

like this one but imagine that the 'mono' has not been prepended.

lua
3 Answers

You can use table.insert:

cmd = { omnisharp_bin, '--languageserver', '--hostPID', tostring(vim.fn.getpid()) }
table.insert(cmd, 1, 'mono')
-- cmd is now what you want

You can use either table.insert(mytable, position, value) to insert value at position position and shift all the values after that over, or use table.insert(table, value) to insert a value at the end of the array part.

user_5732550

And imagine cmd is an object and can handle all by itself...

cmd = setmetatable({ omnisharp_bin,
 '--languageserver',
 '--hostPID',
 tostring(vim.fn.getpid()) },
 {__index = table}) -- This adds all table functions to cmd

cmd:insert(1, 'mono')

print(cmd:concat(' ',1 , #cmd))
-- As LMD wrote in comment, 1 and #cmd not really needed here
-- It shows concat()' default behaviour and could inspire
-- That you can pick with concat() a range of numbered keys
-- Or only one with: cmd:concat('', 1, 1)
-- Especially the zero and also negativ numbers

Important: cmd.insert() means: Use from cmd
( like table.insert(cmd, 1, 'mono') )
cmd:insert() means: Use with cmd
( Without cmd as first argument )

user_117407580

To answer it myself (since I was also diving into this question before I saw these answers. thanks):

cmd = { 'mono', unpack(cmd) }

I think this one might be slow, but it's simple so it's elegant.

user_52905190
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