Efraim Flashner <efr...@flashner.co.il> writes:
> +(define (wc-l-command file)
> + (let* ((input-file (open-file file "r"))
> + (line (read-line input-file))
> + (line-count 0))
> + (while (not (eof-object? line))
> + (set! line-count (1+ line-count))
> + (set! line (read-line input-file)))
> + line-count))
It’s unusual for me to see the use of “while” and “set!” in Scheme code.
You could do this in a functional manner using a fold (see SRFI-1) or
with file streams (see SRFI-41), which also provides a stream-fold.
The idea with a fold is that you have a function that takes a value
(e.g. from a list or a stream) and an intermediate result. The function
does something to the value and then returns a new intermediate result.
Here’s a fold over a list of symbols implementing a count:
(fold
(lambda (_ res) (+ res 1)) ; increase the result
0 ; start at 0
'(hello world bye)) ; items to count
If you had a file stream, where each element represents one line, you
can fold over all lines in much the same way to get a count. You could
use the same framework with a different stream element generator
(reading one word or byte at a time instead of one line at a time) to
implement the other features of “wc”.
There’s an example of how to define a file stream in the Guile manual in
the documentation for SRFI-41.
~~ Ricardo
