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Fast Expression Evaluation

Palash Biswas

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25 Feb 2010CPOL

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Use Expression += Value instead of Expression = Expression + Value. Since Expression can be arbitrarily complex, this can result in lots of unnecessary work. This forces the JIT to evaluate both copies of Expression, and many times this is not needed. The first statement can be optimized far...

Use Expression += Value instead of Expression = Expression + Value.
Since Expression can be arbitrarily complex, this can result in lots of unnecessary work. This forces the JIT to evaluate both copies of Expression, and many times this is not needed. The first statement can be optimized far better than the second, since the JIT can avoid evaluating the Expression twice.

N.B: Expression it self is a Variable not "Expression"..

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By

Palash Biswas

Software Developer Kovair Inc.

India

I have started programming in 10 years on Fortran 77.Then it was Cobol,C,C++,JAVA 1.2, ASP,JavaScript. Now it at all C# and .NET Framework, such tehnologies as WCF, ADO.NET, ASP.NET, LINQ, ASP.NET Ajax , FLEX and another.

Comments and Discussions

Expression = Expression + Value???

Rozis24-Feb-10 10:47

24-Feb-10 10:47

"Use Expression += Value instead of Expression = Expression + Value."

You mean something like this?

(x/2)=(x/3)+5 must be (x/2)+=5 ????

I'll bet this will not work because it is not: Expression = Expression + Value
but: Variable = Variable + Expression (where Variable is any identity in your language that may contain a value)

Since Variable can NOT be arbitrarily complex your whole story goes...

Remark: Variable += Value gains the time needed to access Variable.

Re: Expression = Expression + Value??? [modified]

Palash Biswas25-Feb-10 3:34

25-Feb-10 3:34

Everyone know that x/2+=x/3+5 is not a valid statement in any programming language.This is completely a erronious statement.
Everyone know that this is not a big things to say.... I think if someone has a little knowledge about any programming language, He/She can not say this..Thanking you for your innovative thinking..

modified on Monday, March 1, 2010 11:05 PM

Re: Expression = Expression + Value???

dwilliss25-Feb-10 15:51

25-Feb-10 15:51

However, expression could be something such as:

SomeDictionary(key) = SomeDictionary(key) + 1

As long as the expression can be interpreted as both an lvalue and and rvalue, the author's statement still holds true.

And besides, not only is

SomeDictionary(key) += 1

faster, I find it easier to read. I just wish VB had the ++ and -- operators.

Re: Expression = Expression + Value???

Palash Biswas25-Feb-10 17:10

25-Feb-10 17:10

Of course it is easier to read..

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