expression-parser

Parses and evaluates expression

TODO

HParser function

Supported operations:

"+, -, *, /" - standard arithmetical operations

"!, =, !=, and, or, xor" - standard boolean operations

"%" - remainder (modulus) operation

">, <, >=, <=" - comparison operations

"someObject.someField" - evaluate value of 'someField' of 'someObject'

"has, has not" - tests if collection has (or has not) specified element

"like, not like" - tests if value matches regexp

"++" - adds one collection to another

"--" - computes difference between two collections

Supported functions:

"case" - takes two arguments: index and collection. Returns value placed in collection with specified index

"isEmpty" - tests whether value is empty

"isExists" - tests whether value is present in context

"length" - returns length of collection or string. Boolean argument is a special case: function returns '1' in case of 'true' and '0' in case of 'false'

"upper, lower" - returns string in upper or lower case

"split" - takes two arguments: string and separator and returns collection made by splitting of incoming string by specified separator

"indexOf" - takes two arguments: string and substring. Returns the index within this string of the first occurrence of the specified substring

"substr" - takes 2 or 3 arguments: string, beginIndex[, endIndex] - returns substring of string

"compareIgnoreCase" - compares two strings ignoring their case

Values representation:

Values of fields of some object should be dot-separated:
```
user.field.subField
```
Strings can be written with or without quotes of apostrophes:
```
someString
'someString'
"someString"
```
Numbers should be written as is, without any additional symbols

Examples:

 user.isDefined
 !user.isDefined
 user.isDefined = true 
 user.isDefined != true
 user.roles has "qa"
 user.roles has not "admin"
 (user.isDefined = true) and (user.roles has "qa") 
 (user.isDefined) and (user.roles has "qa")) 
 (!user.isDefined) or (user.roles has "admin")