When SRFI 32 Sort Libraries was withdrawn, it had 28 procedures. Having many variants in a general-purpose sorting library has disadvantages: This SRFI’s sort procedures operate on lists and arrays, which includes vectors, the merge procedures operate on lists. SRFI 32’s vector routines took optional arguments to restrict their operations to a subrange of the vector. SRFI 63 shared subarrays (using make-shared-array or SLIB’s subarray) eliminate the need for these optional arguments. The present SRFI procedures take an optional procedure argument equivalent to Common-Lisp’s &KEY argument. The sorted?, merge, and merge! procedures consume asymptotic time and space no larger than O(N), where N is the sum of the lengths of the sequence arguments. The sort and sort! procedures consume asymptotic time and space no larger than O(N*log(N)), where N is the length of the sequence argument. All five functions take an optional key argument corresponding to a CL-style `&key’ argument. A less? predicate with a key argument behaves like: Returns #f when the sequence contains at least one out-of-order pair. It is an error if the sequence is not a list or array (including vectors and strings). Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Source.