Binary insertion

1 files changed, 36 insertions, 1 deletions

diff --git a/list.vim b/list.vim
index 8857af1..44d6b20 100644
--- a/list.vim
+++ b/list.vim
@@ -1,6 +1,6 @@
 " Vim auto-load script
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: March 15, 2011
+" Last Change: August 31, 2011
 " URL: http://peterodding.com/code/vim/misc/
 
 " Remove duplicate values from {list} in-place (preserves order).
@@ -20,4 +20,39 @@ function! xolox#misc#list#unique(list)
   return a:list
 endfunction
 
+" Binary insertion (more efficient than calling sort() after each insertion).
+
+function! xolox#misc#list#binsert(list, value, ...)
+  let idx = s:binsert_r(a:list, 0, len(a:list), a:value, exists('a:1') && a:1)
+  return insert(a:list, a:value, idx)
+endfunction
+
+function! s:binsert_r(list, low, high, value, ignorecase)
+  let mid = a:low + (a:high - a:low) / 2
+  if a:low == a:high
+    return a:low
+  elseif a:ignorecase ? a:value >? a:list[mid] : a:value > a:list[mid]
+    return s:binsert_r(a:list, mid + 1, a:high, a:value, a:ignorecase)
+  elseif a:ignorecase ? a:value <? a:list[mid] : a:value < a:list[mid]
+    return s:binsert_r(a:list, a:low, mid, a:value, a:ignorecase)
+  else
+    return mid
+  endif
+endfunction
+
+if 0
+  " Tests for xolox#misc#list#binsert().
+  let s:list = ['a', 'B', 'e']
+  function! s:test(value, expected)
+    call xolox#misc#list#binsert(s:list, a:value, 1)
+    if s:list != a:expected
+      call xolox#misc#msg#warn("list.vim: Test failed! Expected %s, got %s",
+            \ string(a:expected), string(s:list))
+    endif
+  endfunction
+  call s:test('c', ['a', 'B', 'c', 'e'])
+  call s:test('D', ['a', 'B', 'c', 'D', 'e'])
+  call s:test('f', ['a', 'B', 'c', 'D', 'e', 'f'])
+endif
+
 " vim: ts=2 sw=2 et