Highlight identical strings in vi(m)

Question

One feature of Notepad++, which I find really useful and haven't found elsewhere, is the highlighting of other text that is identical to the one currently selected.

Is there something similar possible with vi(m)? (Of course, there is. But how do I achieve it?) That is, any of those:

• If I am in Visual Mode and have text selected: Highlight identical text

• If I have searched /foo, highlight all instances of foo.

• If I am at the beginning of a string (series of characters, numbers or underscores), highlight all other matching strings (prefered solution).

The last one is similar to the closing parentheses matching and IMHO the most useful.

Edit: For my second use case, I found a solution (that is, Google found it...):

:set hls

However, the others remain.

Answer 1

For your third requirement,

nnoremap , :mat Error "<C-R><C-W>"<CR>

Put this in your vimrc file..
Press comma to highlight all occurrences of the word at cursor.
Also, pressing * or # will highlight all occurrences of the string at cursor when hlsearch is set
edit:
For your first requirement,

vnoremap <silent> , :<C-U>
  \let old_reg=getreg('"')<Bar>let old_regtype=getregtype('"')<CR>
  \gvy:mat Error "<C-R><C-R>=substitute(
  \escape(@", '/".*$^~['), '_s+', '\_s\+', 'g')<CR>"<CR>
  \gV:call setreg('"', old_reg, old_regtype)<CR>

Found this here. Modified to your needs.

Answer 2

:help hlsearch

 When there is a previous search pattern, highlight all its matches.

so, put

set hlsearch

to your vimrc

Answer 3

For door number three, that is what the # key does. It will also jump to the beginning of the previous string of such. Asterisk(*) does the opposite: jump to the beginning of the next string of such.