How to generate a string by concatenating another string with an environment variable

Question

I need to create a variable with a fool folder direct which need to concatenate from a environment variable and the end notes

function! MyFoo(arg)
    let repo=$Project + "/cfora"                #Q1      
    let build=$project + "/build/cfora/debug"   
    exec "!cd build"                            
    exec "!cmake repo"                          #02
endfunction

Question:

Q1: How can I concatenate the value of the environment variable $Project with the end node string /cfora into one string and assign it to a new variable repo?

Q2: How can I refer the variable in the string not print the variable name? For example here, I want to ultimately run cmake /root/to/the/project/repo, not cmake repo

Answer 1

In vim dot is a concatenation operator:

let repo = $Project . '/cfora'

To "refer" variable in the string, well, in your case it is just a concatenation again:

exe '!cmake ' . repo

PS

I would suggest to use built in make facilities for this.

And vim lcd instead of exe '!cd ...