Abstract syntax tree for logic expressions

Build an AST (JSON object) from a logic expression string

Input

    const logicExpression = 'a AND b OR c';

Processing

    const bracketTree = new BracketTree();
    bracketTree.applyExpression(expr) // handle errors
    const logicTree = new LogicTree(bracketTree.root)

Output

    console.log(logicTree.root);

    {
      name: 'node0',
      content: 'a AND b OR c',
      orParams: [{
        text: 'a AND b',
        andParams: [{ name: 'a' }, { name: 'b' }]
      }, {
        text: 'c',
        andParams: [{ name: 'c' }]
      }]
    }

Logical operators

• Logical negation NOT
• Logical conjunction AND
  • Logical NAND
• Logical disjunction OR
  • Logical NOR
  • Logical exclusive disjunction XOR
  • Logical equality XNOR

Logical truth table

Different syntax in programming and natural languages

https://en.wikipedia.org/wiki/Logical_connective

From boolean expression to logic tree

Input boolean expression: (true OR false) AND NOT(false) OR true OR false

1. Create a binary boolean expression tree

2. Skip logical negation operator (NOT, ~)

• A negation operator is unary. It applicable for one node only.
• Put it as a property of the corresponding node of the tree: node.isNegation = true

3. Transform all binary logical operators to basic: conjunction and disjunction

• a NAND b == NOT(A AND B)
• a XOR b == (a OR b) AND (a NAND b)
• a XNOR b == NOT(a XOR b)

4. Order of precedence (priority) for basic syntax operators

5. Define own relations between basic logical binary operators

• AND can contain only ORs (1 to many)
• OR can contain only ANDs (1 to many)

6. Build an abstract syntax tree, using rules above

    // input
    (a OR b) AND NOT(c) OR d OR e

    // output
    {
      name: 'node0',
      content: '(a OR b) AND NOT(c) OR d OR e',
      orParams: [{
        text: '(a OR b) AND NOT(c)',
        andParams: [{
          name: 'node0',
          content: 'a OR b',
          orParams: [{
            text: 'a',
            andParams: [{ name: 'a' }]
          }, {
            text: 'b',
            andParams: [{ name: 'b' }]
          }]
        }, {
          name: 'c',
          isNegation: true
        }]
      }, {
        text: 'd',
        andParams: [{ name: 'd' }]
      }, {
        text: 'e',
        andParams: [{name: 'e' }]
      }]
    }

Where:

• nodeX - specific name for a parameter, which contains a group of other parameters, where X - order number of a node in a list of operators
• isNegation - adds Logical negation (NOT) to the corresponding parameter

7. Use this logic tree for any business purposes

• calculate a result of a logic expression: a>3 AND a<5 == false // (if a = 8)
• build a presentational string, using any syntax (SQL, JAVA, PASCAL, etc.): a AND b OR NOT c --> a && b || !c
• draw a tree diagram for any logic expression
• build a decision tree
• etc.