Support for unknown variables

[IvoTops]

Implemented support for getting no value for a variable and treating it as null. Evaluating x + y will be null if either x or y is unknown and not throw an error anymore.

• IFunction has new property CanHandleNullArguments. Set to true if the function needs and/or recognizes IsNull values. Set to false to let the code set the result automatically to IsNull if any argument for the function is null.
• Added IfNull() and NullIf() functions to handle null values inside your formulas! => IfNull(x,-1)<0 will be TRUE if x is unknown at evaluation time.
• NULL as text in a formula will be interpreted as a variable set to null, so => IfNull(null,1) will evaluate to 1
• Results from Calcxxx are now changed to reflect nullable outcomes => double?, bool?,..
• New EvaluatorValueTypeKey Null. Can be checked with IsNull property
• default(EvaluatorValue) and default(InternalEvaluatorValue) will be treated as a null value
• implicit conversions with double?, datetime?, .. added
• Added testcases for Null handling
• Added VariablesUsed() function with some overloads to get a list of the variables a formula contains
• Fixed equals comparison for non number values
• Added Benchmark for evaluating solely evaluating performance (common usecase=> parse once, evaluate again and again with new values)

Documentation is not yet updated

[IvoTops]

Ok, will fix. Is there an easy way to get the same settings in my visual studio?

On Sun, 17 Jul 2022 at 21:02, Vitaly @.***> wrote:

@.**** requested changes on this pull request.

Can't review other files until you fix namespace design

In NoStringEvaluating.Extensions.Microsoft.DependencyInjection/NoStringEvaluating.Extensions.Microsoft.DependencyInjection.csproj https://github.com/KovtunV/NoStringEvaluating/pull/4#discussion_r922882385 :

@@ -37,4 +36,8 @@

Don't change this file pls, it should refer to nuget

In NoStringEvaluating/Contract/INoStringEvaluator.cs https://github.com/KovtunV/NoStringEvaluating/pull/4#discussion_r922882650 :

@@ -5,416 +5,417 @@ using NoStringEvaluating.Models.Values; using NoStringEvaluating.Nodes.Common;

-namespace NoStringEvaluating.Contract;

-///

-/// Expression evaluator -///

-public interface INoStringEvaluator +namespace NoStringEvaluating.Contract

Don't change design for namespaces, please, fix in all files. Have you rebased successfully?

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[KovtunV]

Ok, will fix. Is there an easy way to get the same settings in my visual studio?

To change namespace design? Yes, it should be in Visual Studio

[IvoTops]

To rebase I fetched upstream from the master and that has the 'old' namespace design. If I change the namespace design in visual studio and apply that it will also apply all my other code formatting settings. I see no option in vs to selectively apply only the namespace design change. Could you run your coding style settings over the pull request and re-commit?

[IvoTops]

If you think that works better please do that. I have been on GitHub for a while but have only recently started contributing and using PR and such.

On Fri, Jul 22, 2022, 07:42 Vitaly @.***> wrote:

To rebase I fetched upstream from the master and that has the 'old' namespace design. If I change the namespace design in visual studio and apply that it will also apply all my other code formatting settings. I see no option in vs to selectively apply only the namespace design change. Could you run your coding style settings over the pull request and re-commit?

is it possible? Think will make MR to your master branch with these fixes

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