Class: DecisionAgent::Dmn::Feel::SimpleParser

Inherits:
Object
  • Object
show all
Defined in:
lib/decision_agent/dmn/feel/simple_parser.rb

Overview

Simple regex-based parser for common FEEL expressions Handles arithmetic, logical operators, and simple comparisons Uses operator precedence climbing for correct evaluation order

Constant Summary collapse

ARITHMETIC_OPS = 
%w[+ - * / ** %].freeze
LOGICAL_OPS = 
%w[and or].freeze
COMPARISON_OPS = 
%w[>= <= != > < =].freeze
PRECEDENCE =

Operator precedence (higher number = higher precedence)

{
  "or" => 1,
  "and" => 2,
  "=" => 3,
  "!=" => 3,
  "<" => 4,
  "<=" => 4,
  ">" => 4,
  ">=" => 4,
  "+" => 5,
  "-" => 5,
  "*" => 6,
  "/" => 6,
  "%" => 6,
  "**" => 7
}.freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ SimpleParser

Returns a new instance of SimpleParser.



35
36
37
38
 
# File 'lib/decision_agent/dmn/feel/simple_parser.rb', line 35

def initialize
  @tokens = []
  @position = 0
end

Class Method Details

.can_parse?(expression) ⇒ Boolean

Check if expression can be handled by simple parser

Returns:



41
42
43
44
45
46
47
48
49
 
# File 'lib/decision_agent/dmn/feel/simple_parser.rb', line 41

def self.can_parse?(expression)
  expr = expression.to_s.strip
  # Can't handle: lists, contexts, functions, quantifiers, for expressions
  return false if expr.match?(/[\[{]/) # Lists or contexts
  return false if expr.match?(/\w+\s*\(/) # Function calls
  return false if expr.match?(/\b(some|every|for|if)\b/) # Complex constructs

  true
end

Instance Method Details

#parse(expression) ⇒ Object

Parse expression and return AST-like structure

Raises:



52
53
54
55
56
57
58
59
60
 
# File 'lib/decision_agent/dmn/feel/simple_parser.rb', line 52

def parse(expression)
  expr = expression.to_s.strip
  raise DecisionAgent::Dmn::FeelParseError, "Empty expression" if expr.empty?

  @tokens = tokenize(expr)
  @position = 0

  parse_expression
end