Apex Rules Engine

Engine to parse an expression with logical and comparion operators (.e.g 1 && 2 && (3 || 4)), set the values of each token in the statement, and evaluate to a boolean.

Usage

Pass a string to the logical parser, set the values of the tokens in the expression, and then set the expression. Value of tokens can be set as :

• Double, for example 123.23
• Integer - for example 34
• Boolean - for example, True or False

Logical Operators Supported

Operator	Usage
&&	AND
||	OR
!	NOT

Comparison Operators Supported

Operator	Usage
>	Greater than
<	Less than
=	Equal to
!=	Not Equal to
>=	Greater than or equal to
<=	Less than or equal to

Evaluate '1 && 2'

LogicParser.Expression exp = 
    new LogicParser().parseLogicalExpression('1 && 2');

exp.set('1', true)
exp.set('2', true);
System.assertEquals(true, exp.evaluate());

exp.set('1', true)
exp.set('2', false);
System.assertEquals(false, exp.evaluate());

Evaluate '( 1 && 2 ) || ( 3 && 4 )'

LogicParser.Expression exp = 
    new LogicParser().parseLogicalExpression('( 1 && 2 ) || ( 3 && 4 )');

exp.set('1', false);
exp.set('2', false);
exp.set('3', true);
exp.set('4', true);
System.assertEquals(true, exp.evaluate());

exp.set('1', true);
exp.set('2', true);
exp.set('3', false);
exp.set('4', false);
System.assertEquals(true, exp.evaluate());

exp.set('1', true);
exp.set('2', false);
exp.set('3', true);
exp.set('4', false);
System.assertEquals(false, exp.evaluate());

Evaluate !( 1 && 2 )

LogicParser.Expression exp =  new LogicParser().parseLogicalExpression('!( 1 && 2 )');

exp.set('1', false);
exp.set('2', false);
System.assertEquals(true, exp.evaluate());

exp.set('1', true);
exp.set('2', true);
System.assertEquals(false, exp.evaluate());

Evaluate (0 != 2) && ( 3 < 4 )

LogicalOperationHelper.Expression exp = new LogicalOperationHelper().parseLogicalExpression('(0 != 2) && ( 3 < 4 )');

exp.set('0', 5000);
exp.set('2', 5000);
exp.set('3', 4000);
exp.set('4', 6000);
System.assertEquals(false, exp.evaluate());

Evaluate (1 >= 2) || (3 <= 4)

LogicParser.Expression exp = new LogicParser().parseLogicalExpression('(1 >= 2) || (3 <= 4)');
exp.set('1', 6000);
exp.set('2', 6000);
exp.set('3', 3000);
exp.set('4', 4000);

System.assertEquals(true, exp.evaluate());

Evaluate (1 = 2) || (3 != 4)

LogicParser.Expression exp = new LogicParser().parseLogicalExpression('(1 = 2) || (3 != 4)');
exp.set('1', 6000);
exp.set('2', 6000);
exp.set('3', 3000);
exp.set('4', 4000);

System.assertEquals(true, exp.evaluate());