Fixes incorrect values in prev_prime()

Fixes #529
mhostetter · Dec 1, 2023 · 852e92f · 852e92f
1 parent 4984e40
commit 852e92f
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Showing 2 changed files with 13 additions and 2 deletions.
diff --git a/src/galois/_prime.py b/src/galois/_prime.py
@@ -176,7 +176,7 @@ def prev_prime(n: int) -> int:
     while True:
         for shift in shifts:
             i = base + shift  # May be bigger than n
-            if i >= n:
+            if i > n:
                 continue
             if is_prime(i):
                 return i

diff --git a/tests/test_primes.py b/tests/test_primes.py
@@ -47,6 +47,17 @@ def test_prev_prime(prev_prime):
         assert galois.prev_prime(x) == z
 
 
+def test_prev_prime_large():
+    """
+    https://github.com/mhostetter/galois/issues/529
+    """
+    assert galois.prev_prime(100000034) == 100000007
+    assert galois.prev_prime(100000035) == 100000007
+    assert galois.prev_prime(100000036) == 100000007
+    assert galois.prev_prime(100000037) == 100000037
+    assert galois.prev_prime(100000038) == 100000037
+
+
 def test_next_prime_exceptions():
     with pytest.raises(TypeError):
         galois.next_prime(20.0)
@@ -58,7 +69,7 @@ def test_next_prime(next_prime):
         assert galois.next_prime(x) == z
 
 
-def test_next_prime_bug_528():
+def test_next_prime_large():
     """
     https://github.com/mhostetter/galois/issues/528
     """