conditional map in normal mode?

Question

Is it possible in vim to do a conditional map, in normal mode? I've seen it for insert mode. I want to remap gq, depending on the outcome of a function. Something like:

nnoremap gq if(g:set_formatprg()) | gq | else | = | endif

Notice that g:set_formatprg() will not always have the same value, so it cannot be replaced by

if(!g:set_formatprg()) | nnoremap gq = | endif

Answer 1

An expression map makes it easy

nnoremap <expr> gq g:set_formatprg() ? 'gq' : '='

For more help see

:h map-expression