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Fix a bug when mixing floating point with integer (#32)
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* Add a check that ensures that the Min/Max functions run in the
	highest precision of the 2 parameters. Originally only the type of
	the first parameter was checked. Fixes a bug that would cause
	Min(2,1.97) to return 2 because 1.97 was converted to an int
	during expression evaluation.
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@bradtglass @sklose
bradtglass authored and sklose committed Aug 16, 2019
1 parent 1ff7b74 commit 19359d6
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Showing 2 changed files with 151 additions and 26 deletions.
165 changes: 139 additions & 26 deletions src/NCalc/Numbers.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
using System;
using System.Collections;
using System.Security.Cryptography;

namespace NCalc
{
Expand Down Expand Up @@ -1775,32 +1777,32 @@ public static object Max(object a, object b)
return a;
}

TypeCode typeCodeA = a.GetTypeCode();
TypeCode typeCode = ConvertToHighestPrecision(ref a, ref b);

switch (typeCodeA)
switch (typeCode)
{
case TypeCode.Byte:
return Math.Max((Byte)a, Convert.ToByte(b));
return Math.Max((Byte)a, (Byte)b);
case TypeCode.SByte:
return Math.Max((SByte)a, Convert.ToSByte(b));
return Math.Max((SByte)a, (SByte)b);
case TypeCode.Int16:
return Math.Max((Int16)a, Convert.ToInt16(b));
return Math.Max((Int16)a, (Int16)b);
case TypeCode.UInt16:
return Math.Max((UInt16)a, Convert.ToUInt16(b));
return Math.Max((UInt16)a, (UInt16)b);
case TypeCode.Int32:
return Math.Max((Int32)a, Convert.ToInt32(b));
return Math.Max((Int32)a, (Int32)b);
case TypeCode.UInt32:
return Math.Max((UInt32)a, Convert.ToUInt32(b));
return Math.Max((UInt32)a, (UInt32)b);
case TypeCode.Int64:
return Math.Max((Int64)a, Convert.ToInt64(b));
return Math.Max((Int64)a, (Int64)b);
case TypeCode.UInt64:
return Math.Max((UInt64)a, Convert.ToUInt64(b));
return Math.Max((UInt64)a, (UInt64)b);
case TypeCode.Single:
return Math.Max((Single)a, Convert.ToSingle(b));
return Math.Max((Single)a, (Single)b);
case TypeCode.Double:
return Math.Max((Double)a, Convert.ToDouble(b));
return Math.Max((Double)a, (Double)b);
case TypeCode.Decimal:
return Math.Max((Decimal)a, Convert.ToDecimal(b));
return Math.Max((Decimal)a, (Decimal)b);
}

return null;
Expand All @@ -1825,36 +1827,147 @@ public static object Min(object a, object b)
return a;
}

TypeCode typeCodeA = a.GetTypeCode();
TypeCode typeCode = ConvertToHighestPrecision(ref a,ref b);

switch (typeCodeA)
switch (typeCode)
{
case TypeCode.Byte:
return Math.Min((Byte)a, Convert.ToByte(b));
return Math.Min((Byte)a, (Byte)b);
case TypeCode.SByte:
return Math.Min((SByte)a, Convert.ToSByte(b));
return Math.Min((SByte)a, (SByte)b);
case TypeCode.Int16:
return Math.Min((Int16)a, Convert.ToInt16(b));
return Math.Min((Int16)a, (Int16)b);
case TypeCode.UInt16:
return Math.Min((UInt16)a, Convert.ToUInt16(b));
return Math.Min((UInt16)a, (UInt16)b);
case TypeCode.Int32:
return Math.Min((Int32)a, Convert.ToInt32(b));
return Math.Min((Int32)a, (Int32)b);
case TypeCode.UInt32:
return Math.Min((UInt32)a, Convert.ToUInt32(b));
return Math.Min((UInt32)a, (UInt32)b);
case TypeCode.Int64:
return Math.Min((Int64)a, Convert.ToInt64(b));
return Math.Min((Int64)a, (Int64)b);
case TypeCode.UInt64:
return Math.Min((UInt64)a, Convert.ToUInt64(b));
return Math.Min((UInt64)a, (UInt64)b);
case TypeCode.Single:
return Math.Min((Single)a, Convert.ToSingle(b));
return Math.Min((Single)a, (Single)b);
case TypeCode.Double:
return Math.Min((Double)a, Convert.ToDouble(b));
return Math.Min((Double)a, (Double)b);
case TypeCode.Decimal:
return Math.Min((Decimal)a, Convert.ToDecimal(b));
return Math.Min((Decimal)a, (Decimal)b);
}

return null;
}


private static TypeCode ConvertToHighestPrecision(ref object a, ref object b)
{
TypeCode typeCodeA = a.GetTypeCode();
TypeCode typeCodeB = b.GetTypeCode();

if (typeCodeA==typeCodeB)
return typeCodeA;

if (!(TypeCodeBitSize(typeCodeA, out bool floatingPointA) is int bitSizeA))
return TypeCode.Empty;
if (!(TypeCodeBitSize(typeCodeB, out bool floatingPointB) is int bitSizeB))
return TypeCode.Empty;

if (floatingPointA != floatingPointB)
{
if (floatingPointA)
{
b = ConvertTo(b, typeCodeA);

return typeCodeA;
}
else
{
a = ConvertTo(a, typeCodeB);

return typeCodeB;
}
}

if (bitSizeA > bitSizeB)
{
b = ConvertTo(b, typeCodeA);

return typeCodeA;
}
else
{
a = ConvertTo(a, typeCodeB);

return typeCodeB;
}

}

private static int? TypeCodeBitSize(TypeCode typeCode,out bool floatingPoint)
{
floatingPoint = false;
switch (typeCode)
{
case TypeCode.SByte: return 8;
case TypeCode.Byte: return 8;
case TypeCode.Int16: return 16;
case TypeCode.UInt16: return 16;
case TypeCode.Int32: return 32;
case TypeCode.UInt32: return 32;
case TypeCode.Int64: return 64;
case TypeCode.UInt64: return 64;
case TypeCode.Single:
floatingPoint = true;
return 32;
case TypeCode.Double:
floatingPoint = true;
return 64;
case TypeCode.Decimal:
floatingPoint = true;
return 128;
default: return null;
}
}

private static object ConvertTo(object value, TypeCode toType)
{
switch (toType)
{
case TypeCode.Byte:
return Convert.ToByte(value);

case TypeCode.SByte:
return Convert.ToSByte(value);

case TypeCode.Int16:
return Convert.ToInt16(value);

case TypeCode.UInt16:
return Convert.ToUInt16(value);

case TypeCode.Int32:
return Convert.ToInt32(value);

case TypeCode.UInt32:
return Convert.ToUInt32(value);

case TypeCode.Int64:
return Convert.ToInt64(value);

case TypeCode.UInt64:
return Convert.ToUInt64(value);

case TypeCode.Single:
return Convert.ToSingle(value);

case TypeCode.Double:
return Convert.ToDouble(value);

case TypeCode.Decimal:
return Convert.ToDecimal(value);
}

return null;
}
}
}
12 changes: 12 additions & 0 deletions test/NCalc.Tests/Fixtures.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -655,6 +655,18 @@ public void ShouldAddDoubleAndDecimal()

Assert.Equal(11M, e.Evaluate());
}

[InlineData("Min(2,1.97)",1.97)]
[InlineData("Max(2,2.33)",2.33)]
[Theory]
public void ShouldCheckPrecisionOfBothParametersForMaxAndMin(string expression, double expected)
{
var e=new Expression(expression);

var result = e.Evaluate();

Assert.Equal(expected,result);
}
}
}

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