Allow setVar to null and better unit tests

Improved unit tests (#74)

* Variable fixes (#67)

* Reproduce if throws UnknownOperatorException

* Fix variable detection

* Adding IncorrectNumberOfFunctionParametersException

* Removing tabs

* Better exception message text

* Handler for not found variables (#68)

* Added handler to define not found variables
Added support for string variables
Fixed strings and ints comparison error

* Check if variables have scalar types (int, float, string and bool)
Better $onVarNotFound logic

* Release prep (#69)

* String comparison unit tests

* getVars and getFunctions sanity checks

* Add dynamic variable documentation

* Better setVar error message (#70)

Additional unit tests
Readme update

* Improved support for null variables (#72)

* Added handler to define not found variables
Added support for string variables
Fixed strings and ints comparison error

* Check if variables have scalar types (int, float, string and bool)
Better $onVarNotFound logic

* Better support for null variables

* Better support for null variables

* Better support for null variables

* Allow null values in `setVar` method (#73)

* Added handler to define not found variables
Added support for string variables
Fixed strings and ints comparison error

* Check if variables have scalar types (int, float, string and bool)
Better $onVarNotFound logic

* Better support for null variables

* Better support for null variables

* Better support for null variables

* Allow null values in `setVar` method

* Better unit testing

Co-authored-by: Javier Marín <javier@marinros.com>

Improved Support for NULL variables

Improved support for null variables (#72)

* Added handler to define not found variables
Added support for string variables
Fixed strings and ints comparison error

* Check if variables have scalar types (int, float, string and bool)
Better $onVarNotFound logic

* Better support for null variables

* Better support for null variables

* Better support for null variables

Better error message for setVar

Better setVar error message (#70)

Additional unit tests
Readme update

Dynamic Variables

Undefined variable handler allows for delayed computation of variables. Perfect for seldom used variables that may be expensive to compute on initialization of MathExecutor.

Variables working

Fixed variables and added better exception messages

Code style and MathExecutorException namespace fix

MathExecutorException had incorrect namespace on setVar not being passed a numeric value.

Packagist Badge

• Added Packagist badge to README.md
• $variables is now private, as it was in V1

New tokenizer and executor

• New tokenizer without regular expressions
• Simpler code structure
• Better performance
• ~20% less memory usage
• PHP >=7.1 support
• Division by zero default is now to throw DivisionByZeroException. Call setDivisionByZeroIsZero to default to V1 behavior.

Support for negative numbers starting bracketed expressions

Negative expression start (#60)

* Update documentation for PHPFUI/InstaDoc

* Support for negative numbers starting paren enclosed expressions

PHP 7.4 support

• Unary -0 support
• PHP 7.4 support for TravisCI
• Unit Test Cleanup
• Documentation tweaks