add x and X commands

not originally planned, but would be nice to have a counterpart to i/I

README.md

@@ -40,5 +40,7 @@ implementation status of planned features:
 - [x] s - ce-command-reg-replace
 - [ ] t - ce-command-copy
 - [x] w - ce-command-write
+- [x] x - ce-command-chop
+- [x] X - ce-command-chop-beg
 - [x] 0 - ce-command-number
 

ce.cl

@@ -30,6 +30,8 @@
  (#\s . ce-command-reg-replace)
  (#\t . ce-command-copy)
  (#\w . ce-command-write)
+ (#\x . ce-command-chop)
+ (#\X . ce-command-chop-beg)
  (#\0 . ce-command-number)
  (#\1 . ce-command-number)
  (#\2 . ce-command-number)
@@ -69,10 +71,21 @@
   "return nil if numeric or newline"
   (not (or (digit-char-p c) (char= #\Newline c))))
 
+(defun string-or (a b)
+  "or but first being empty is equivalent to nil"
+  (or (if (string= "" a) nil a) b))
+
 (defun ce-mod (num div)
   "modulus but handle zero"
   (if (= 0 div) 0 (mod num div)))
 
+(defun ce-apply-region (fun)
+  "apply fun to each line of region"
+  (let ((mlen (list-length buffer)))
+   (let ((in (ce-mod inpoint mlen)) (out (1+ (ce-mod outpoint mlen))))
+    (let ((new (mapcar fun (subseq buffer in out))))
+     (ce-replace-lines in out new)))))
+
 (defun ce-push-line (index line)
   "push a line into the buffer at index"
   (if (= 0 index) ; index 0 is special as buffer is a singly linked list
@@ -347,11 +360,8 @@ specific command. the recognized commands are as follows:
   "helper for insert and insert-beg"
   `(progn
     (ce-reset-input)
-    (let ((inp (read-line)) (mlen (list-length buffer)))
-     (let ((in (ce-mod inpoint mlen)) (out (1+ (ce-mod outpoint mlen))))
-      (let ((new (mapcar (lambda (x) (concat ,a ,b))
-		  (subseq buffer in out))))
-       (ce-replace-lines in out new))))))
+    (let ((inp (read-line)))
+     (ce-apply-region (lambda (x) (concat ,a ,b))))))
 
 (defun ce-command-insert (&optional c)
   "add to the end of each line in region"
@@ -423,6 +433,26 @@ specific command. the recognized commands are as follows:
 			:if-does-not-exist :create)
     (format out "~{~a~%~}" buffer))))
 
+(defmacro ce-build-chop (fin)
+  "helper for chop and chop-beg"
+  `(progn
+    (ce-reset-input)
+    (let ((inp (parse-integer (string-or (read-line) "1"))))
+     (ce-apply-region (lambda (x)
+		       (let ((llen (length x)))
+			(if (< llen inp)
+			 x ,fin)))))))
+
+(defun ce-command-chop (&optional c)
+  "chop off argument characters from end of each line in region"
+  (declare (ignore c))
+  (ce-build-chop (subseq x 0 (- llen inp))))
+
+(defun ce-command-chop-beg (&optional c)
+  "chop off argument characters from start of each line in region"
+  (declare (ignore c))
+  (ce-build-chop (subseq x inp)))
+
 (defun ce-command-number (c)
   "input a number"
   (if (or (= 0 newpoint) (= 2 newpoint))