Removing a character from a list in Scheme

Question

For example

I have a file testing.txt that reads

read 3 4

Consider

(define file(open-input file "testing.txt"))

I want to remove the r in read instead of the whole word, I want to update file without the first character r, I know I can not use this using cdr file because it erases the word read.

Any suggestions?

Óscar López Óscar López · Accepted Answer · 2012-05-06T23:03:33

A couple of hints for your homework. This will return a list, with each line of the file as a string in the list:

(define lines (file->lines "testing.txt"))

This procedure will write an input text to a file in the given path, overwriting the contents of the file:

(define (write-to-a-file path txt)
  (call-with-output-file path
    (lambda (output-port)
      (display txt output-port))
    #:exists 'replace))

You can use the procedures string->list, list->string (see the documentation), car and cdr to manipulate the list returned by file->lines, and write the resulting text using write-to-a-file. Now you have all you need to solve the problem by yourself.

Removing a character from a list in Scheme

1 Answers