The wasBinarySearchTreeSearch function takes as arguments:

• a binary search tree (BST) as a flattened list as per binary_trees.
• the root of the binary search tree (root)
• the node (node) to search for in the binary search tree.

and returns the node in the binary search tree, or the empty string otherwise.

// Ord() function, written by Pedro Oval, 2010-05-28
// Inlined by Wizardry and Steamworks
integer Ord(string chr) {
    if (chr == "") return 0;
    string hex = llEscapeURL(chr);
    if (llGetSubString(hex, 0, 0) != "%") 
        return llBase64ToInteger("AAAA" + 
            llStringToBase64(llGetSubString(chr, 0, 0)));
    integer b = (integer)("0x" + llGetSubString(hex, 1, 2));
    if (b < 194 || b > 244) return b;
    if (b < 224) return ((b & 0x1F) << 6) | 
        (integer)("0x" + llGetSubString(hex, 4, 5)) & 0x3F;
    if (b < 240) return (b & 0x0F) << 12 + 
        ((integer)("0x" + llGetSubString(hex, 4, 5)) & 0x3F) << 6 + 
        (integer)("0x" + llGetSubString(hex, 7, 8)) & 0x3F;
    return (b & 0x07) << 18 + 
        ((integer)("0x" + llGetSubString(hex, 4, 5)) & 0x3F) << 12 + 
        ((integer)("0x" + llGetSubString(hex, 7, 8)) & 0x3F) << 6 + 
        (integer)("0x" + llGetSubString(hex, 10, 11)) & 0x3F;
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2013 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
integer wasOrdCompare(string chra, string chrb) {
    // numerical
    float fa = (float)chra;
    float fb = (float)chrb;
    if(fa != 0 && fb != 0) {
        if(fa > fb) return 1;
        if(fa < fb) return -1;
        return 0;
    }
    // lexical
    if(llStringLength(chra) == 0 && llStringLength(chrb) == 0) return 0;
    if(llStringLength(chra) && llStringLength(chrb) == 0) return 1;
    if(llStringLength(chra) == 0 && llStringLength(chrb)) return -1;
    string a = llGetSubString(chra, 0, 0);
    chra = llDeleteSubString(chra, 0, 0);
    string b = llGetSubString(chrb, 0, 0);
    chrb = llDeleteSubString(chrb, 0, 0);
    integer oa = Ord(a);
    integer ob = Ord(b);
    if(oa > ob) return 1;
    if(oa < ob) return -1;
    return wasOrdCompare(chra, chrb);
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2013 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
string wasBinaryTreeSearch(list BST, string root, string node) {
    integer i = llListFindList(BST, (list)root);
    string pivotRoot = llList2String(BST, i);
    string left = wasBinaryTreeLeft(BST, pivotRoot);
    string right = wasBinaryTreeRight(BST, pivotRoot);
    integer compare = wasOrdCompare(node, pivotRoot);;
    if(compare > 0) {
        if(right == "") return "";
        return wasBinaryTreeSearch(BST, right, node);
    }
    if(compare < 0) {
        if(left == "") return "";
        return wasBinaryTreeSearch(BST, left, node);
    }
    return pivotRoot;
}