VIM Single Compile command from insert mode

问题

I'm following Mapping keys in Vim - Tutorial (Part 1) - 6.2 Insert mode maps, and there it says:

The <C-R>= command doesn't create a new undo point.
You can also call Vim functions using the <C-R>= command:

:inoremap <F2> <C-R>=MyVimFunc()<CR>

I'm trying to use this to call SingleCompile#Compile() like:

map! <F5> <C-R>=SingleCompile#Compile()<CR>

It's working, but the problem is that when I get back to insert mode, a 0 character is inserted as a side-effect.

Why is this and how can I avoid it?

EDIT:

I'm using <C-R> because it doesn't create a undo point and has the purpose of calling a function instead of entering a command like <C-O> does. I don't want to create a undo point.

EDIT:

I've updated the VIM wiki based on the ternary operator trick provided by Ingo Karkat.

回答1:

The implicit return value of a function is 0. You need to either modify SingleCompile#Compile() or write a wrapper that returns the empty string:

function! SingleCompileWrapper()
    call SingleCompile#Compile()
    return ''
endfunction

map! <F5> <C-R>=SingleCompileWrapper()<CR>

An alternative clever trick is to evaluate the function inside the ?: ternary operator:

map! <F5> <C-R>=SingleCompile#Compile()?'':''<CR>

回答2:

The '0' is the return value of the function, which is naturally inserted into the buffer when called in insert mode

Use <C-O> instead of <C-R> to leave the insert mode for the comand

回答3:

I wouldn't recommend that approach, but how about the redneck solution (just delete the 0 after-the-fact):

map! <F5> <C-R>=SingleCompile#Compile()<CR><BS>

Seriously, for those situations where <C-R> cannot be used, and you have to leave insert mode, :undojoin may help.

来源：https://stackoverflow.com/questions/11686210/vim-single-compile-command-from-insert-mode

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