Re: [Chicken-users] ftl egg

[Thomas Christian Chust]

felix winkelmann wrote:

> [...]
> If you have any suggestions for algorithms and functions to add, please
> tell us so.
> [...]

Hello Felix,

playing around with the ftl egg, I noticed the following behaviour that
looks broken to me:

  - The interfaces v=vector and v=string contain length methods that
    return an element of the vector / string instead of its length.
  - The interfaces i=reverse-vector, i=reverse=string and i=reverse-%v
    don't transverse their input from the end but rather return
    (length <input>) times the first element.

A patch against the current subversion trunk fixing these things is
attached to the e-mail.

Additionally I suggest the following handy output and accumulator
interfaces:

  ;;; A string output collector.
  (define o=string
    (o-interface
     ;; create
     (lambda (#!optional dst)
       (or dst ""))
     ;; write
     (lambda (obj out)
       (conc out obj))
     ;; result
     identity))

  (define a=string
    (a=%o o=string))

cu,
Thomas

-- 
Murphy's Law is recursive.  Washing your car to make it rain doesn't work.

Index: ftl.scm
===================================================================
--- ftl.scm     (revision 4762)
+++ ftl.scm     (working copy)
@@ -505,9 +505,10 @@
      (unwrap
       in
       (lambda (data start end)
-       (if (fx< end start)
+       (if (fx>= start end)
            (values)
-           (values (v-ref data start) (sub data start (fx- end 1)))))))))
+           (let ((i (fx- end 1)))
+             (values (v-ref data i) (sub data start i)))))))))
 
 (define i=list
   (i-interface
@@ -532,9 +533,10 @@
      (unwrap
       in
       (lambda (d s e)
-       (if (fx< e s)
+       (if (fx>= s e)
            (values)
-           (values (vector-ref d s) (sub d s (fx- e 1)))))))))
+           (let ((i (fx- e 1)))
+             (values (vector-ref d i) (sub d s i)))))))))
 
 (define i=string
   (i-interface
@@ -552,9 +554,10 @@
      (unwrap
       in
       (lambda (d s e)
-       (if (fx< e s)
+       (if (fx>= s e)
            (values)
-           (values (string-ref d s) (sub d s (fx- e 1)))))))))
+           (let ((i (fx- e 1)))
+             (values (string-ref d i) (sub d s i)))))))))
 
 (define i=port
   (i-interface
@@ -610,9 +613,10 @@
      (unwrap
       in
       (lambda (data start end)
-       (if (fx< end start)
+       (if (fx>= start end)
            (values)
-           (values (v-ref data start) (sub data start (fx- end 1)))))))
+           (let ((i (fx- end 1)))
+             (values (v-ref data i) (sub data start i)))))))
    (lambda (in)
      (unwrap
       in
@@ -696,14 +700,14 @@
 (define v=vector
   (v-interface 
    (lambda (vec)
-     (unwrap vec (lambda (d s e) (vector-ref d s))) )
+     (unwrap vec (lambda (d s e) (fx- e s))) )
    (lambda (vec n)
      (unwrap vec (lambda (d s e) (vector-ref d (fx+ s n))) ) ) ) )
 
 (define v=string
   (v-interface 
    (lambda (vec)
-     (unwrap vec (lambda (d s e) (string-ref d s))) )
+     (unwrap vec (lambda (d s e) (fx- e s))) )
    (lambda (vec n)
      (unwrap vec (lambda (d s e) (string-ref d (fx+ s n))) ) ) ) )