simplify implementation of bsearch to use "until" and avoid "last"; tested

builtin.c

@@ -1614,18 +1614,18 @@ static const char* const jq_builtins[] = {
   "  else . as $in"
   ""   // # state variable: [start, end, answer]
   ""   // # where start and end are the upper and lower offsets to use.
-  "    | last( [0, length-1, null]"
-  "            | while( .[0] <= .[1] ;"
-  "                     (if .[2] != null then (.[1] = -1)"              // # i.e. break
-  "                      else"
-  "                        ( ( (.[1] + .[0]) / 2 ) | floor ) as $mid"
-  "                        | $in[$mid] as $monkey"
-  "                        | if $monkey == target  then (.[2] = $mid)"  // # success
-  "                          elif .[0] == .[1]     then (.[1] = -1)"    // # failure
-  "                          elif $monkey < target then (.[0] = ($mid + 1))"
-  "                          else (.[1] = ($mid - 1))"
-  "                          end"
-  "                      end )))"
+  "    | [0, length-1, null]"
+  "    | until( .[0] > .[1] ;"
+  "             if .[2] != null then (.[1] = -1)"              // # i.e. break
+  "             else"
+  "               ( ( (.[1] + .[0]) / 2 ) | floor ) as $mid"
+  "               | $in[$mid] as $monkey"
+  "               | if $monkey == target  then (.[2] = $mid)"  // # success
+  "                 elif .[0] == .[1]     then (.[1] = -1)"    // # failure
+  "                 elif $monkey < target then (.[0] = ($mid + 1))"
+  "                 else (.[1] = ($mid - 1))"
+  "                 end"
+  "             end )"
   "    | if .[2] == null then"         // # compute the insertion point
   "         if $in[ .[0] ] < target then (-2 -.[0])"
   "         else (-1 -.[0])"