nse/client: Allow NaN as standard deviation.

See <https://bugs.gnunet.org/view.php?id=7021#c18399>.

* doc/scheme-gnunet.tm
  (Estimation of the size of the network)[estimate:standard-deviation]:
  Document it.

1 files changed, 8 insertions, 3 deletions

diff --git a/gnu/gnunet/nse/client.scm b/gnu/gnunet/nse/client.scm
index 7b0c6dd..d240c28 100644
--- a/gnu/gnunet/nse/client.scm
+++ b/gnu/gnunet/nse/client.scm
@@ -36,7 +36,7 @@
           estimate)
   (import (only (rnrs base)
                 begin define quote lambda case values expt = else apply
-                and >=)
+                and >= let or nan?)
           (only (rnrs control)
                 when unless)
           (only (rnrs records syntactic)
@@ -104,7 +104,7 @@ in @var{estimate} as a positive flonum (possibly zero or infinite)."
     (define (estimate:standard-deviation estimate)
       "Return the standard deviation of the logarithmic estimate
 of the number of peers of the last 64 rounds as a positive flonum
-(possibly zero or infinite)."
+(possibly zero or infinite), or not-a-number."
       (%estimate:standard-deviation estimate))
 
     (define (estimate:number-peers estimate)
@@ -147,7 +147,12 @@ even if not connected.  This is an idempotent operation."
                    (sizeof /:msg:nse:estimate '()))
                 ;; XXX: these two lines below are not tested
                 (>= (read% /:msg:nse:estimate '(size-estimate) slice) 0)
-                (>= (read% /:msg:nse:estimate '(std-deviation) slice) 0)))
+                ;; See <https://bugs.gnunet.org/view.php?id=7021#c18399> for
+                ;; situations in which the deviation can be infinite or NaN.
+                (let ((stddev
+                       (read% /:msg:nse:estimate '(std-deviation) slice)))
+                  (or (>= stddev 0)
+                      (nan? stddev)))))
           ((handle! slice) (handle-estimate! slice)))))
       (define (send-start!)
         ;; The service only starts sending estimates once