[hackers] [libzahl] Fix a small error in the solution for Powers of the golden ratio || Mattias Andrée

[git]

commit 89898de3bfa38d39494555a3e109253489a0e0b6
Author:     Mattias Andrée <maand...@kth.se>
AuthorDate: Mon Jul 25 16:56:20 2016 +0200
Commit:     Mattias Andrée <maand...@kth.se>
CommitDate: Mon Jul 25 16:56:25 2016 +0200

    Fix a small error in the solution for Powers of the golden ratio
    
    Signed-off-by: Mattias Andrée <maand...@kth.se>

diff --git a/doc/exercises.tex b/doc/exercises.tex
index e89c2b3..93f77e4 100644
--- a/doc/exercises.tex
+++ b/doc/exercises.tex
@@ -508,7 +508,7 @@ but for efficiency and briefness, we will use
 void golden_pow(z_t r, z_t p)
 \{
     if (zsignum(p) <= 0)
-        zsetu(r, zzero(p));
+        zsetu(r, zcmpi(p, -1) >= 0);
     else
         lucas(r, p);
 \}