Switch between C++ source/test/header in Vim

vimrc

"switch between .h / -inl.h / .cc / .py / .js / _test.* / _unittest.* with ,h       
",i ,c ,p ,j ,t ,u                                                                 
""(portion from old mail from David Reiss)                                         
let pattern = '\(\(_\(unit\)\?test\)\?\.\(cc\|js\|py\)\|\(-inl\)\?\.h\)$'          
nmap ,c :e <C-R>=substitute(expand("%"), pattern, ".cc", "")<CR><CR>               
nmap ,h :e <C-R>=substitute(expand("%"), pattern, ".h", "")<CR><CR>                
nmap ,i :e <C-R>=substitute(expand("%"), pattern, "-inl.h", "")<CR><CR>            
nmap ,t :e <C-R>=substitute(expand("%"), pattern, "_test.", "") . substitute(expand("%:e"), "h", "cc", "")<CR><CR>
nmap ,u :e <C-R>=substitute(expand("%"), pattern, "_unittest.", "") . substitute(expand("%:e"), "h", "cc", "")<CR><CR>
nmap ,p :e <C-R>=substitute(expand("%"), pattern, ".py", "")<CR><CR>               
nmap ,j :e <C-R>=substitute(expand("%"), pattern, ".js", "")<CR><CR>