Conditional Nested Boolean Statements

November 27th, 2011, 02:18 PM

Hi all,

This is less of a NinjaTrader specific question and more of a question on how the C# compiler works. It is a pretty nit-picky question best suited for programming experts. Let me explain my question:

I'm trying to make my strategy efficient. As with any programming language, there a lots of if/then statements. My question arises from what I can do in other languages. C# is new to me. My native tongue is Pascal and Ada. In the latter, I can do this:

Code

if A and B and C thenDoThis; 
end if;

In this case, the compiler always evaluates A, B, and C --- even if A is false. On the other hand, one can write:

Code

if A and if B and if C thenDoThis; 
end if;

The extra ifs added above function the same. But, if A is false, Boolean statements B and C are never evaluated. The result is the same, but is (very slightly) less computational intensive. The "and if" statement is an elegant way to write the ugly:

Code

if A thenif B thenif C then 
DoThis; 
end if;
end if;
end if;

[The "or" statement equivalent is "or else" (e.g. if A and B or else C then...). ]

Question: Can I do the same sort of thing in C# without resorting to ugly nested if/then statements?

Thanks!

November 27th, 2011, 04:03 PM

Good question. I think that you can do it.

I have attached two indicators in the zip file below. Both are identical versions of the SuperTrend, but there is a small difference in lines 74 and 75 of the code

The first indicator, SuperTrendErrorCode uses

Code

if (ChartControl.ChartStyleType == ChartStyleType.CandleStick)
	candles = true;

If you call this indicator from another indicator, you will get an error, because there is no chart and ChartControl will throw an exception in OnStartUp().

The second indicator, SuperTrendCorrectedCode uses

Code

if (ChartControl != null && ChartControl.ChartStyleType == ChartStyleType.CandleStick)
              candles = true;

In this case NinjaTrader will not throw an exception, because the first statement is false and the second statement is not executed.

I would conclude from this behavior that you do not need to use nested statements.

But I am clearly no expert for C#, so you may want to ask somebody else.

November 27th, 2011, 05:17 PM

serac

Hi all,

This is less of a NinjaTrader specific question and more of a question on how the C# compiler works. It is a pretty nit-picky question best suited for programming experts. Let me explain my question:

I'm trying to make my strategy efficient. As with any programming language, there a lots of if/then statements. My question arises from what I can do in other languages. C# is new to me. My native tongue is Pascal and Ada. In the latter, I can do this:

Code

if A and B and C thenDoThis; 
end if;

In this case, the compiler always evaluates A, B, and C --- even if A is false. On the other hand, one can write:

Code

if A and if B and if C thenDoThis; 
end if;

The extra ifs added above function the same. But, if A is false, Boolean statements B and C are never evaluated. The result is the same, but is (very slightly) less computational intensive. The "and if" statement is an elegant way to write the ugly:

Code

if A thenif B thenif C then 
DoThis; 
end if;
end if;
end if;

[The "or" statement equivalent is "or else" (e.g. if A and B or else C then...). ]

Question: Can I do the same sort of thing in C# without resorting to ugly nested if/then statements?

Thanks!

C# uses short-circuit evaluation for && and ||, so it will only evaluate as much as needed to have the full result. so false && false will only evaluate the first false as it is enough to conclude the entire expression is false. true || true will only evaluate the first true as it is enough.

C# does have binary operators for and/or that evaluates all arguments, & and | these will evaluate both arguments.

November 27th, 2011, 06:44 PM

@FatTails and @ktrader: Thanks for the reply! Looks like && is built-in to function as "and if" as I described. Makes sense, I guess. Thanks, again!

Conditional Nested Boolean Statements

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Conditional Nested Boolean Statements