Vim snippets with arguments

Question

I'm trying to create snippets without using any plugins. For instance,

nnoremap ,eq :-1read $HOME/.vim/snips/.eq.tex<CR>o<TAB>

inserts the contents of .eq.tex:

\begin{equation}

\end{equation}

I would like to do the same thing except be able to pass a simple character argument so that ,for i produces

for (int i = 0; i < n; ++i) { }

while ,for j gives

for (int j = 0; j < n; ++j) { }

Is something like this possible? One possibility could be to use functions,

function! For(idx)
    r$HOME/.vim/snips/.for.c
endfunction

But this takes us back to the same problem. Or should I be defining mappings to :command functions, as in the 5th answer of this post?

Answer 1

To get a single character to use as an "argument" in a mapping, you can use the getchar() function, which waits for one.

You should then use nr2char() to convert it to a string.

If you want to use the character more than once (as it's your case here), you should store it in a variable. It's easier if you use a function to do so. Then use an <expr> mapping to insert the return value of the function into the buffer.

Putting it all together:

function! SnippetFor()
  let v = nr2char(getchar())
  return printf("for (int %s = 0; %s < n; %s++) {}\<Left>", v, v, v)
endfunction

inoremap <expr> ,for SnippetFor()

Activate it with ,fori or ,forj in Insert mode. You might want to tweak how the braces work or something like that.

But, really, use a snippet manager. It's way more flexible and you get to define your snippets at a much higher level! Not to mention you can find libraries of already defined snippets to get you quickly started.