Typing symbols
- ¬
- ~ !
- ∧
- & ^
- ∨
- | v (between spaces)
- →
- -> => ⊃
- ↔
- <-> <=> ≡
- ↑ ↓
- NAND, NOR (keypad)
- ⊤ ⊥
- always true / always false
Type the whole formula, then press Enter (or click Build). The builder only checks whether it’s a wff at that point.
Sentence letters are capitals like A, B, C (A1, P2 also work). As in the textbook, ¬ applies to what immediately follows it and outer parentheses can be dropped. Mixing binary connectives without parentheses, as in A ∧ B ∨ C, is ambiguous, so the builder asks you to add them. Chains of a single ∧ or ∨ (A ∧ B ∧ C) are fine.