[PATCH 1/2] rdelim: Add new procedure `for-rdelim-in-port`.

From 302159fe61d9df526911ead8ea6ad823ad8b0443 Mon Sep 17 00:00:00 2001
From: AwesomeAdam54321 <[email protected]>
Date: Sun, 15 Dec 2024 23:48:30 +0800
Subject: [PATCH 1/2] rdelim: Add new procedure `for-rdelim-in-port`.

* module/ice-9/rdelim.scm (for-rdelim-in-port): Add it.
(for-delimited-in-port): Define as a specialised `for-rdelim-in-port`.
(for-line-in-file): Define as a specialised `for-delimited-in-port`.

These procedures provide a backbone for parsing, with domain-specific
logic implemented as a separate procedure to be passed as an argument.
---
 module/ice-9/rdelim.scm | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/module/ice-9/rdelim.scm b/module/ice-9/rdelim.scm
index d2cd081d7..0bbaaf904 100644
--- a/module/ice-9/rdelim.scm
+++ b/module/ice-9/rdelim.scm
@@ -23,7 +23,10 @@
 ;;; similar to (scsh rdelim) but somewhat incompatible.
 
 (define-module (ice-9 rdelim)
-  #:export (read-line
+  #:export (for-delimited-in-port
+            for-line-in-file
+            for-rdelim-in-port
+            read-line
             read-line!
             read-delimited
             read-delimited!
@@ -206,3 +209,33 @@ characters to read.  By default, there is no limit."
 	      line)
       (else
        (error "unexpected handle-delim value: " handle-delim)))))
+
+(define* (for-rdelim-in-port port proc rdelim-proc
+                             #:key (stop-pred eof-object?))
+  "Call PROC for every (RDELIM-PROC PORT) in PORT until STOP-PRED returns #t.
+RDELIM-PROC has to advance through PORT with every call."
+  (let loop ((rdelim (rdelim-proc port)))
+    (cond ((stop-pred rdelim)
+           (close-port port))
+          (else
+           (proc rdelim)
+           (loop (rdelim-proc port))))))
+
+(define* (for-delimited-in-port port proc
+			        #:key (delims "\n") (handle-delim 'trim))
+  "Call PROC for every delimited line in PORT until the eof-object is reached."
+  (for-rdelim-in-port port proc
+		      (lambda (port)
+			(read-delimited delims port handle-delim))))
+
+(define* (for-line-in-file file proc
+                           #:key (encoding #f) (guess-encoding #f))
+  "Call PROC for every line in FILE until the eof-object is reached.
+FILE must be a filename string.
+
+The line provided to PROC is guaranteed to be a string."
+  (call-with-input-file
+      file
+    (lambda (port)
+      (for-delimited-in-port port proc))
+    #:encoding encoding #:guess-encoding guess-encoding))
-- 
2.41.0