Interface:Sandbox

Well-formed formulas
(An experimental, edited version of the master copy at Interface:Classical propositional calculus).

We first introduce the kind of well-formed formulas and a few variables for this kind.  kind (wff) var (wff p q r s) 

Logical connectives
There are five standard logical connectives in the classical propositional calculus, negation,  term (wff (¬ wff))  implication,  term (wff (→ wff wff))  disjunction,  term (wff (∨ wff wff))  conjunction,  term (wff (∧ wff wff))  and, finally, the biconditional,  term (wff (↔ wff wff))  In addition, one can also consider the constant formulas (or nullary connectives) "the true",  term (wff (⊤))  and "the false",  term (wff (⊥)) 