Formal system

• basic (untyped) lambda calculus
• boolean logic

External links

• Experiencing systems as a puzzle game - very good! http://incredible.pm/

Wikipedia

• Formal_system, Formal_language, Formal_grammar (Abstract_syntax_tree, Backus–Naur_form)
• Rewriting and Substitution
• Chomsky_hierarchy

---

• Boolean_algebra (De Morgan's laws)
• Propositional_calculus, Second-order_propositional_logic (Second-order_logic), Higher-order_logic

---

• Intuitionistic_logic, Intuitionistic_type_theory, Curry–Howard_correspondence
• Lambda_calculus, Simply_typed_lambda_calculus, Typed_lambda_calculus
• Evaluation_strategy

---

• Foundations_of_mathematics, Category_theory
• Categorical_logic Bicartesian_closed_category (Homotopy type theory, Lawvere theories)

---

• Calculus_of_constructions, Formal_verification, Automated_theorem_proving, Symbolic_computation, Computer_algebra_system