;;; File:
;;;   read-line.ss
;;; Author:
;;;   Samuel A. Rebelsky
;;; Version:
;;;   1.0 of 20 September 2006
;;; Summary:
;;;   A set of procedures to help you read lines from a file.  Taken
;;;   from the reading on files.
;;; History:
;;;   At end.

; +------------+------------------------------------------------------
; | Procedures |
; +------------+

;;; Procedure:
;;;   read-line
;;; Parameters:
;;;   source, an input port
;;; Purpose:
;;;   Read one line of input from a source and return that line
;;;   as a string.
;;; Produces:
;;;   line, a string
;;; Preconditions:
;;;   The source is open for reading. [Unverified]
;;; Postconditions: 
;;;   Has read characters from the source (thereby affecting
;;;     future calls to read-char and peek-char).
;;;   line represents the characters in the file from the
;;;     "current" point at the time read-line was called
;;;     until the first end-of-line or end-of-file character.
;;;   line does not contain a newline.
(define read-line
  (lambda (source)
    ; Read all the characters remaining on the line and
    ; then convert them to a string.
    (list->string (read-line-of-chars source))))

;;; Procedure:
;;;   read-line-of-chars
;;; Parameters:
;;;   source, an input port
;;; Purpose:
;;;   Read one line of input from a source and return that line
;;;   as a list of characters.
;;; Produces:
;;;   chars, a list of characters.
;;; Preconditions:
;;;   The source is open for reading. [Unverified]
;;; Postconditions: 
;;;   Has read characters from the source (thereby affecting
;;;     future calls to read-char and peek-char).
;;;   chars represents the characters in the file from the
;;;     "current" point at the time read-line was called
;;;     until the first end-of-line or end-of-file character.
;;;   chars does not contain a newline.
(define read-line-of-chars
  (lambda (source)
    ; If we're at the end of the line or the end of the file,
    ; then there are no more characters, so return the empty list.
    (cond
      ; If we're at the end of the file, there are no more characters,
      ; so return the empty list.
      ((eof-object? (peek-char source)) null)
      ; If we're at the end of the line, we're done with the line
      ; skip over the end-of-line character and return the empty list.
      ((char=? (peek-char source) #\newline) (read-char source) null)
      ; Otherwise, read the current character, read the remaining 
      ; characters, and join them together.
      (else (cons (read-char source) (read-line-of-chars source))))))

; +---------+---------------------------------------------------------
; | History |
; +---------+

; Wednesday, 20 September 2006 (v 1.0) [Samuel A. Rebelsky]
; * Created.