Merge commit 'v3.3.0' into upstream

[debian/gnuradio] / gnuradio-core / src / utils / partition-cascaded-decimating-filters.scm

diff --git a/gnuradio-core/src/utils/partition-cascaded-decimating-filters.scm b/gnuradio-core/src/utils/partition-cascaded-decimating-filters.scm
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+;; Estimate the total work (ntaps * sampling rate) for two cascaded
+;; decimating low pass filters.
+;;
+;; The basic assumption is that the number of taps required in any 
+;; section is inversely proportional to the normalized transition width
+;; for that section.
+;;
+;; FS is the input sampling frequency
+;; F1 is the cutoff frequency
+;; F2 is the far edge of the transition band
+;; DEC1 is the decimation factor for the first filter
+;; DEC2 is the decimation factor for the 2nd filter
+;;
+;; The total decimation factor is DEC1 * DEC2.  Therefore,
+;; the output rate of the filter is FS / (DEC1 * DEC2)
+
+(require 'common-list-functions)
+(require 'factor)
+
+
+
+(define (work2 fs f1 f2 dec1 dec2)
+  (+ (work1 fs f1 (/ fs (* 2 dec1)) dec1)
+     (work1 (/ fs dec1) f1 f2 dec2)))
+
+
+;; work for a single section
+
+(define (work1 fs f1 f2 dec)
+  (/ (* fs (/ fs (- f2 f1))) dec))
+
+
+;; return the max integer dec such that fs/(2*dec) >= f2
+
+(define (max-dec fs f2)
+  (inexact->exact (floor (/ fs (* 2 f2)))))
+
+
+;; `adjoin' returns the adjoint of the element OBJ and the list LST.
+;;  That is, if OBJ is in LST, `adjoin' returns LST, otherwise, it returns
+;;  `(cons OBJ LST)'.
+
+(define (adjoin-equal obj lst)
+  (if (member obj lst) lst (cons obj lst)))
+
+
+;;; not quite right
+
+(define (permute lst)
+  (let ((result '()))
+    (define (aux set head)
+      (if (null? set)
+         (set! result (cons head result))
+         (for-each (lambda (x)
+                     (aux (set-difference set (list x))
+                          (cons x head)))
+                   set)))
+    (aux lst '())
+    result))
+
+;; `extract-nth' returns the Nth element of LST consed on to the
+;; list resulting from splicing out the Nth element of LST.
+;; Indexing is 0 based.
+
+(define (extract-nth n lst)
+  lst)
+
+  
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