In Racket, Gauche, MIT, Gambit, Chicken, Bigloo, Kawa, Chibi, SCM,
Vicare, Scheme 9, RScheme, S7, BDC, XLisp, Spark, Inlab, Sagittarius,
read-line returns the next line from the specified or current input
port, stripping the trailing end of line.
In STklos it returns two values, the line and the end of line.
In Rep it returns the line including the end of line.
Assume a file foo.txt whose contents are foo\rbar.
What is the return value of each of the following expressions?
(read-line (open-input-file "foo.txt"))
(read-line (open-input-string "foo\rbar"))| Implementation | File port | String port |
|---|---|---|
| Racket | "foo\rbar" |
Same |
| Gauche | "foo" |
Same |
| Chibi | "foo\rbar" |
"foo" |
| Chicken | "foo\\rbar" |
"foo" |
| MIT | "foo\rbar" |
Same |
| Gambit | "foo\rbar" |
Same |
| Kawa | "foo" |
Same |
In the source code of MIT Scheme (src/runtime/textual-port.scm),
string ports and file ports are both wrapped in the record type
<textual-port-type>. So when using read-line the same interface is
invoked.
But in Chibi and Chicken, there is no such wrapper. read-line
directly treats a string port and a file port differently. That is why
the output is different.