普通Lisp连接和换行符

Question

I am currently writing a LISP program which analyses the CR results in the form of lists like following: ("I" 0 10 0 20) << (word X0 X1 Y0 Y1)

It must build the whole text using positions of words. My code has a cluster analyser which finds out cluster layouts like paragraphs with left- alignment or right or even both. A cluster data structure seems like this: ("cluster name" xline y0 y1 '(cluster words))

How can i add a new line while i am iterating over a list of strings and concatenate them into result string to create a formatted text from these? Example:

"Hi,\n
\n
here is my entry\n
\n
Good bye"

My code seems like following:

(defun print-formatted-text(txt)
  (let
      ((size   (array-total-size txt))
       (sorted (sort (sort txt #'compare-mix) #'compare-generic2))
       (result ""))
    (loop for i from 0 to (1- size) do
          (let ((el (aref sorted i)))
            (if (word? el)
                (setf result (concatenate 'string result (first el) " "))
              (if (null (nth 7 el))
                  nil
                (progn
                  (setf result (concatenate 'string result " "))
                  (dolist (curr (nth 7 el))
                    (setf result (concatenate 'string result (first curr) " "))))))))
    result))

If the current data isn't a word, then it is a paragraph. It means, i need to add a new line before i give the words of paragraph out and after.

Is the usage of concatenate properly here?

Thank you for your advices.

Answer 1

I can't quite follow your program, but it's much easier to work with string-streams and use format , write-string , write-line , terpri , and related functions, eg

(let ((lines '("Hi," "Here is my entry" "Good bye")))
  (with-output-to-string (stream)
    (dolist (line lines)
      (write-line line stream)
      (terpri stream))))
=>
"Hi,

Here is my entry

Good bye

"

Answer 2

A few things about coding style

(defun print-formatted-text(txt)
  (let
      ((size   (array-total-size txt))
       (sorted (sort (sort txt #'compare-mix) #'compare-generic2))
       (result ""))
    (loop for i from 0 to (1- size) do
          (let ((el (aref sorted i)))

(LOOP FOR e1 ACROSS sorted

            (if (word? el)
                (setf result (concatenate 'string result (first el) " "))

repeated concatenation of strings is really wasteful. As Xach notes, STREAMS are the better abstraction.

              (if (null (nth 7 el))
                  nil
                (progn

use: (when (nth 7 e1)

                  (setf result (concatenate 'string result " "))
                  (dolist (curr (nth 7 el))
                    (setf result (concatenate 'string result (first curr) " "))))))))
    result))

Answer 3

If you are using concatenate on characters or newline, then you need to enclose in parenthesis so that it is a list, like this '(#\\Newline) .

where #\\Newline is the newline character.

All characters, such as those lifted from a string, like this (elt "abc" 1) need to be made into a list, like this (list (elt "abc" 1) .

For example code:

 (concatenate 'string "Hi ther" '(#\\e) "." '(#\\Newline) "How " (list #\\a #\\r #\\e) " you!" ) => "Hi there. How are you!" 

Answer 4

You can try this

(format nil "~%")

for example

(setf result (concatenate 'string result (format nil "~%")))