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# XSubseq
XSubseq provides functions to be able to handle "subseq"s more effieiently. As Common Lisp's `subseq` copies the data every time, "subseq" and "concatenate" code is very inefficient like the following code.
```common-lisp
(let ((result (make-array 0 :element-type '(unsigned-byte 8))))
(lambda (data start end)
(setf result (concatenate '(simple-array (unsigned-byte 8) (*))
result
(subseq data start end)))
result))
```
XSubseq delays the copying until it is actually needed.
## Usage
```common-lisp
(defvar *data1* #(1 2 3))
(defvar *data2* #(4 5 6))
(xsubseq *data1* 0 1)
;=> #S(XSUBSEQ:XSUBSEQ :DATA #(1 2 3) :START 0 :END 1 :LEN 1)
(xnconc (xsubseq *data1* 0 1)
(xsubseq *data2* 2))
;=> #S(XSUBSEQ:CONCATENATED-XSUBSEQS
; :LEN 2
; :LAST (#S(XSUBSEQ:XSUBSEQ :DATA #(4 5 6) :START 2 :END 3 :LEN 1))
; :CHILDREN (#S(XSUBSEQ:XSUBSEQ :DATA #(1 2 3) :START 0 :END 1 :LEN 1)
; #S(XSUBSEQ:XSUBSEQ :DATA #(4 5 6) :START 2 :END 3 :LEN 1)))
(coerce-to-sequence
(xnconc (xsubseq *data1* 0 1)
(xsubseq *data2* 2)))
;=> #(1 6)
(with-xsubseqs (result)
(xnconcf result (xsubseq *data1* 0 1))
(xnconcf result (xsubseq *data2* 2)))
;=> #(1 6)
```
## Installation
```common-lisp
(ql:quickload :xsubseq)
```
## Author
* Eitaro Fukamachi (e.arrows@gmail.com)
## Copyright
Copyright (c) 2014 Eitaro Fukamachi (e.arrows@gmail.com)
## License
Licensed under the BSD 2-Clause License.
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