Merge pull request #1679 from iamdefinitelyahuman/sqrt-maxnum

Avoid overflow on sqrt of Decimal upper bound
vyperlang · Nov 5, 2019 · 181c70d · 181c70d
2 parents 8e577b3 + f068990
commit 181c70d
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diff --git a/tests/parser/types/numbers/test_sqrt.py b/tests/parser/types/numbers/test_sqrt.py
@@ -142,6 +142,13 @@ def test(a: decimal) -> decimal:
     return c
 
 
+@pytest.mark.parametrize('value', [Decimal(0), Decimal(SizeLimits.MAXNUM)])
+def test_sqrt_bounds(sqrt_contract, value):
+    vyper_sqrt = sqrt_contract.test(value)
+    actual_sqrt = decimal_sqrt(value)
+    assert vyper_sqrt == actual_sqrt
+
+
 @hypothesis.given(
     value=hypothesis.strategies.decimals(
         min_value=Decimal(0),

diff --git a/vyper/functions/functions.py b/vyper/functions/functions.py
@@ -1210,7 +1210,7 @@ def sqrt(expr, args, kwargs, context):
 if x == 0.0:
     z = 0.0
 else:
-    z = (x + 1.0) / 2.0
+    z = x / 2.0 + 0.5
     y: decimal = x
 
     for i in range(256):