hypertino / expression-parser

Expression parser and evaluator for Scala powered by parboiled2.

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This is a ready to use expression parser and evaluator for Scala powered by parboiled2.

Example:

val result = HEval("4*5+3*2").toInt
// result = 26

It's possible to provide a context with variables to the parser:

val context = Obj.from("user"  Obj.from("count"  10))
val result = HEval("4*user.count+1*2", context).toInt
// result = 42

You also can add your own functions into the context:

val context = new ValueContext(Obj.empty) {
    override def function: PartialFunction[(Identifier, Seq[Value]), Value] = {
        case (Identifier(Seq("pow")), args)  args.head.toBigDecimal.pow(args.tail.head.toInt)
    }
}

val result = HEval("pow(2,8)", context).toInt
// result = 256

TODO

  • HParser function

Built-in operators

+, -, *, / - arithmetical operations

!, =, !=, and, or, xor - 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

Built-in 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

Context field access

  1. Values of fields of some object should be dot-separated:
user.field.subField
  1. Strings can be written with quotes of apostrophes (later ignores escapes):
'someString\nabcde' // escaping ignored
"someString\nSecondLine" // newline inserted
  1. Numbers should be written as is, without any additional symbols

Other Examples (TODO)

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")