I want to remap <c-b> to foo<c-b>, being foo a number. However, it seems it won't work with function local variables.
For instance, the following works:
vim9script var foo = 4 if !hasmapto('<c-f>', 'n') nnoremap <expr> <c-f> repeat('<c-f>', foo) endif but the following does not work:
vim9script def Func() var foo = 4 if !hasmapto('<c-f>', 'n') nnoremap <expr> <c-f> repeat('<c-f>', foo) endif enddef Func() Is there any reason for it?
I suspect that foo variable is not accessible when the mapping is executed since it is a local variable from a scope that is invalid long back and not a global variable.
The following should work:
vim9script var foo = 4 def Func() if !hasmapto('<c-f>', 'n') nnoremap <expr> <c-f> repeat('<c-f>', foo) endif enddef Func() 
foo local variable is not accessible anymore and either leading to an error or default to some value different from 4. <c-f> then repeat does not know where to pick foo if it is defined inside the function because it is destroyed when the function finishes, whereas if it is script-local then foo is kept. Hence, foo is valid for the map definition at "script-source-time", but it does not exist at runtime and therefore <c-f> fails. Correct?
:varis not a command, do you intend to use:letas inlet foo = 4instead? I do see an errorE116: Invalid arguments for function repeatiffoohasn't been defined, but as long as the variable is properly defined your second example (which is correct, using<expr>) should work as intended. I'll go ahead and recommend you might want to read Learn Vimscript the Hard Way if you'd like to get more familiar with Vimscript the language and be able to troubleshoot issues like this on your own.varis used in Vim9 to define script-local variables.