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(defmacro cat
    ((&key (to nil)
           (trim '())
           prefix
           postfix)
     &body form#list-of-list)
  (let* ((form#list-of-list#2
          (apply (function append)
                 (mapcar (lambda (list)
                           (list prefix

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===================================

with the following principle
  1 2 (add) = 1 (add 2) = (add 1 2)      
all the following code blocks eval to the same result
i.e. function called "fun" applys to arguments 1 2 3

-----------------------------------

2 1 (sub)

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#include <sys/types.h>
#include <sys/stat.h>
#include <stddef.h>
#include <time.h>

// the following are reported by :  man 2 stat
struct the_stat {
    dev_t     st_dev;         /* ID of device containing file */
    ino_t     st_ino;         /* inode number */
    mode_t    st_mode;        /* protection */

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(define hash-table-preparation-interface
  (interface ()
    hash-table:get-size

    in-cicada-key->key
    create-in-cicada-key
    key->finite-sum
    key-equal?

    hash))

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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(regexp-match-positions
 (regexp
  (cat
   ((object-name (regexp "needle")))
   (" ")
   ((object-name (regexp "needle")))))
 "hay needle needle stack")

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(define-syntax cat
  (syntax-rules ()
    [(cat (str . args))
     (format str . args)]
    [(cat (str . args) (str2 . args2) ...)
     (string-append
      (cat (str . args))
      (cat (str2 . args2) ...))]))

(define-syntax orz

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(letrec ([f (lambda (x) (cons 'a x))]
         [g (lambda (x) (cons 'b (f x)))]
         [h (lambda (x) (g (cons 'c x)))])
  (cons 'd (h '())))
;; (d b a c)

(letrec ([f (lambda (x k) (k (cons 'a x)))]
         [g (lambda (x k) (f x (lambda (v) (k (cons 'b v)))))]
         [h (lambda (x k) (g (cons 'c x) k))])
  (h '() (lambda (v) (cons 'd v))))

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(require (for-syntax syntax/parse))

(define-syntax fun
  (lambda (stx)
    (syntax-parse stx
      #:literals (->)
      [(fun [v ... -> r ...] ...)
       (syntax
        (match-lambda** [(v ...) (begin r ...)] ...))])))

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* 一羣屎殼郎定理

  - 保守力定理
    不動點定理
    一羣屎殼郎定理

  - 假設一
    每個人在解決問題時
    都會使用自己所能想到的最優解法

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命令行中文補全

假設當前路徑下有且僅有 '小學' '數書' '書法' 三個子路徑

當我在命令行裏有如下輸入 ('|' 代表光標的位置)
  cd x|
此時按 <tab> 將爲我做如下補全
  cd 小學/|

當有