Delphi Expression Evaluator

A powerful runtime expression evaluator for Delphi. Parse and evaluate mathematical formulas, logical conditions, string operations, and custom functions at runtime.

For complete documentation, examples, and API reference, visit: danieleteti.it/delphiexprevaluator

Features

Mathematical Operations: +, -, *, /, ^, mod, div with full precedence
Logical Operators: and, or, xor, not with short-circuit evaluation
Pattern Matching: LIKE operator with * and ? wildcards
String Functions: contains(), Length(), Upper(), Lower(), Trim(), Replace(), and more
Date Functions: Now(), Today(), ParseDate(), FormatDate(), DateAdd(), DateDiff()
Aggregation: Min(), Max(), Sort() with variable arguments
Variables: Runtime variable assignment and retrieval
Custom Functions: Register your own functions with lambda syntax
Interface-based API: Automatic memory management, zero leaks

Quick Start

uses ExprEvaluator;
var
  Eval: IExprEvaluator;
begin
  Eval := CreateExprEvaluator;
  // Arithmetic
  Result := Eval.Evaluate('2 + 3 * 4');           // 14
  Result := Eval.Evaluate('power(2, 10)');        // 1024
  // Variables
  Eval.SetVar('price', 100);
  Eval.SetVar('qty', 5);
  Result := Eval.Evaluate('price * qty');         // 500
  // Conditionals
  Result := Eval.Evaluate('if price > 50 then "expensive" else "cheap"');
  // Pattern matching
  Result := Eval.Evaluate('"report.pdf" like "*.pdf"');  // True
  // Short-circuit evaluation
  Result := Eval.Evaluate('false and ExpensiveFunc()');  // ExpensiveFunc NOT called!
end;

Short-Circuit Evaluation

The evaluator implements true short-circuit evaluation:

// AND: if left is false, right is NOT evaluated
Eval.Evaluate('false and SideEffectFunction()');  // Function never called
// OR: if left is true, right is NOT evaluated
Eval.Evaluate('true or SideEffectFunction()');    // Function never called

LIKE Pattern Matching

SQL-style pattern matching with wildcards:

// * matches zero or more characters
Eval.Evaluate('"hello.txt" like "*.txt"');        // True
Eval.Evaluate('"document.pdf" like "doc*"');      // True
// ? matches exactly one character
Eval.Evaluate('"file1.txt" like "file?.txt"');    // True
// Combined patterns
Eval.Evaluate('"backup_2024_01.zip" like "*_????_??.*"'); // True

Eval.RegisterFunction('cube', function(const Args: array of Variant): Variant
  begin
    Result := Power(Args[0], 3);
  end);
Eval.Evaluate('cube(3)');  // 27

Installation

Download or clone from GitHub
Add the source folder to your Library Path
Add uses ExprEvaluator; to your unit

Documentation

Full documentation with all functions, operators, and examples:

danieleteti.it/delphiexprevaluator

Requirements

Delphi 10 Seattle or later
No external dependencies

License

Apache 2.0 - Free for commercial and personal use.

Support

Documentation: danieleteti.it/delphiexprevaluator
Issues: GitHub Issues
Community: Facebook Group