[This article was updated to included changes in v. 1.0.7.2. Originally written for v. 1.0.7.1]

Today, I published a newer version of Mathos Parser on both CodePlex and NuGet. The release notes:

from v.1.0.7.2:

• Force user to use ReadOnlyCollection when using a token list as a parameter.

from v. 1.0.7.1

• Added method GetTokens
• Changed the structure a bit. Now, the Scanner returns tokens instead of continuing with MathParserLogic. This is good if the same kind of expression is to be used many times.

But what does this really mean? Well, previous versions of the parser worked more locally, that is, once one function was executed, it triggered another function, and so on. Now, however, the Scanner (private method) returns a list of tokens instead of launching MathParserLogic directly. If you simply want to get tokens, you would have to execute the GetTokens function, as shown below:

var parser = new MathParser();
parser.LocalVariables.Add("x",10);

var list = parser.GetTokens("(3x+2)");

You can then send the tokens list into either Parse or ProgrammaticallyParse and it will parse it in the same way as if you would enter a string expression, that is:

decimal resultA = parser.Parse("(3x+2)");
decimal resultB = parser.Parse(list);

Both statements above will return 32, but there is one main difference; the execution time will be so much smaller for the second statement, where a “pre-compiled” list is being used. If it would take 100 milliseconds (ms) to find the value of the first statement, it would take approximately 9-10 ms for the second one. The ratio is 10:1.

This is great if you want to perform an operation where the same function is involved several thousands times, for example when approximating an integral.

I am currently thinking about converting math expressions into IL code, but this will happen sometime in future!