Sorting and searching

Neither OpenOffice.org Basic nor the API provide methods or functions for sorting arrays or searching within arrays.

It is quite common to sort almost sorted arrays, for example the list of style names belonging to a style family. Thus, I have found the shell sort to be the fastest for most uses in OpenOffice.org:

sub subShellSort(mArray)

dim n as integer, h as integer, i as integer, j as integer, t as string, Ub as integer, LB as integer
Lb = lBound(mArray)
Ub = uBound(mArray)

' compute largest increment
n = Ub - Lb + 1
h = 1
if n > 14 then
do while h < n
h = 3 * h + 1
loop
h = h \ 3
h = h \ 3
end if
do while h > 0
' sort by insertion in increments of h
for i = Lb + h to Ub
t = mArray(i)
for j = i - h to Lb step -h
if strComp(mArray(j), t, 0) < 1 then exit for
mArray(j + h) = mArray(j)
next j
mArray(j + h) = t
next i
h = h \ 3
loop
end sub

Based on a routine available from a Visual Basic version here.

Searching in a sorted list is compartively efficient with a binary search:

function fnBinarySearch(a, v)
nLeft = 0
nRight = uBound(a)
nLen = len(v)
while nLeft <= nRight
nMid = int((nLeft + nRight)/2)
if left(a(nMid), nLen) = v then
fnBinarySearch = nMid
exit function
elseif v < a(nMid) then
nRight = nMid - 1
else
nLeft = nMid + 1
end if
wend
fnBinarySearch = -1
end function