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Proposed Enhancement: Extend the Rand function to allow seed, min and max #17

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Proposed Enhancement: Extend the Rand function to allow seed, min and max #17

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72 changes: 72 additions & 0 deletions Math expression eval/UnitTest/TestAll.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1188,5 +1188,77 @@ public void Or_Operator_Test()
.Bind("b", 1);
Assert.AreEqual(true, expr4.Eval<bool>());
}

[TestMethod]
public void Rand_0Parameters_Test()
{
var expr1 = new Expression("Rand()");
// Shouldn't error
var _ = expr1.Eval<decimal>();
}

[DataTestMethod]
[DataRow("xxx")]
[DataRow(1d)]
[DataRow(true)]
[DataRow(false)]
public void Rand_1Parameter_Test(object seed)
{
string seedString = seed is string ? $"\"{seed.ToString()}\"" : seed.ToString();
var expr = new Expression($"Rand({seedString})");
var random = new Random(seed.GetHashCode());
var expected = Math.Round(random.NextDouble(), 6);

// Seed should always return same value
Assert.AreEqual(expected, expr.Eval<double>());
}

[TestMethod]
public void Rand_2Parameters_Test()
{
var expr = new Expression("Rand(10,12)");
bool got10 = false;
bool got11 = false;
for (int count = 0; count < 1000; count++)
{
// Either 10 or 11
var actual = expr.Eval<int>();
if (actual == 10)
{
got10 = true;
}
else if (actual == 11)
{
got11 = true;
}
else
{
Assert.Fail("Expected 10 or 11");
}
if (got10 && got11) // Stop if you found a 10 and 11
break;
}

if (!got10 || !got11)
{
Assert.Fail("Expected 10 or 11");
}
}

[DataTestMethod]
[DataRow("seed")]
[DataRow(1d)]
[DataRow(true)]
[DataRow(false)]
public void Rand_3Parameters_Test(object seed)
{
string seedString = seed is string ? $"\"{seed.ToString()}\"" : seed.ToString();
var expr = new Expression($"Rand({seedString},1000,2000)");
var random = new Random(seed.GetHashCode());
var expected = random.Next(1000, 2000);

// Seed should always return same value
Assert.AreEqual(expected, expr.Eval<int>());
}
}
}
56 changes: 52 additions & 4 deletions Math expression eval/org.matheval/Functions/Impl/randFunction.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,15 @@ public class randFunction : IFunction
public List<FunctionDef> GetInfo()
{
return new List<FunctionDef>{
new FunctionDef(Afe_Common.Const_Random, null, typeof(decimal), 0)};
// None
new FunctionDef(Afe_Common.Const_Random, null, typeof(decimal), 0),
// Seed
new FunctionDef(Afe_Common.Const_Random, new[]{ typeof(object) }, typeof(decimal), 1),
// Min, Max
new FunctionDef(Afe_Common.Const_Random, new[]{ typeof(decimal), typeof(decimal) }, typeof(decimal), 2),
// Seed, Min, Max
new FunctionDef(Afe_Common.Const_Random, new[]{ typeof(object), typeof(decimal), typeof(decimal) }, typeof(decimal), 3)
};
}

/// <summary>
Expand All @@ -50,9 +58,49 @@ public List<FunctionDef> GetInfo()
/// <returns>Value</returns>
public Object Execute(Dictionary<string, Object> args, ExpressionContext dc)
{
// Random r = new Random();
//return Afe_Common.Round(r.Next(), dc);
return Convert.ToDecimal(new Random().NextDouble(), dc.WorkingCulture);
Random r = args.Count == 1 || args.Count == 3
? new Random(args[Afe_Common.Const_Key_One].GetHashCode())
: new Random();

switch (args.Count)
{
case 2:
return Convert.ToDecimal
(
r.Next
(
Convert.ToInt32
(
Afe_Common.ToDecimal(args[Afe_Common.Const_Key_One], dc.WorkingCulture)
, dc.WorkingCulture
),
Convert.ToInt32
(
Afe_Common.ToDecimal(args[Afe_Common.Const_Key_Two], dc.WorkingCulture)
, dc.WorkingCulture
)
)
);
case 3:
return Convert.ToDecimal
(
r.Next
(
Convert.ToInt32
(
Afe_Common.ToDecimal(args[Afe_Common.Const_Key_Two], dc.WorkingCulture)
, dc.WorkingCulture
),
Convert.ToInt32
(
Afe_Common.ToDecimal(args[Afe_Common.Const_Key_Three], dc.WorkingCulture)
, dc.WorkingCulture
)
)
);
default:
return Convert.ToDecimal(r.NextDouble(), dc.WorkingCulture);
}
}
}
}