Question

有人能指出我在Scheme中的基本文件I / O操作示例吗？

我只想尝试对文件进行基本的读/写/更新操作。

由于没有适当的资源可供学习，因此很难找到。

Answer 1

在任何符合R5RS的方案中读取/写入文件的最简单方法是：

;; Read a text file
(call-with-input-file "a.txt"
  (lambda (input-port)
    (let loop ((x (read-char input-port)))
      (if (not (eof-object? x))
          (begin
            (display x)
            (loop (read-char input-port)))))))

;; Write to a text file
(call-with-output-file "b.txt"
  (lambda (output-port)
    (display "hello, world" output-port))) ;; or (write "hello, world" output-port)

Scheme具有 ports 的概念，表示可以在其上执行I / O操作的设备。 Scheme的大多数实现都将call-with-input-file和call-with-output-file与文字磁盘文件相关联，您可以安全地使用它们。

Answer 2

这主要是针对具体实施的。鉴于您使用的是球拍，请参阅guide section和the reference manual。

Answer 3

如果您正在使用符合R5RS的计划，请参阅以下帖子：

R5RS Scheme input-output: How to write/append text to an output file?

提出的解决方案如下：

; This call opens a file in the append mode (it will create a file if it doesn't exist)
(define my-file (open-file "my-file-name.txt" "a"))

; You save text to a variable
(define my-text-var1 "This is some text I want in a file")
(define my-text-var2 "This is some more text I want in a file")

; You can output these variables or just text to the file above specified
; You use string-append to tie that text and a new line character together.
(display (string-append my-text-var1 "\r\n" my-file))
(display (string-append my-text-var2 "\r\n" my-file))
(display (string-append "This is some other text I want in the file" "\r\n" my-file))

; Be sure to close the file, or your file will not be updated.
(close-output-port my-file)

文件I / O操作 - 方案

3 个答案: