mathlib3

290ad757 - feat(model_theory/terms_and_formulas): Atomic, Quantifier-Free, and Prenex Formulas (#12557)

feat(model_theory/terms_and_formulas): Atomic, Quantifier-Free, and Prenex Formulas (#12557) Provides a few induction principles for formulas Defines atomic formulas with `first_order.language.bounded_formula.is_atomic` Defines quantifier-free formulas with `first_order.language.bounded_formula.is_qf` Defines `first_order.language.bounded_formula.is_prenex` indicating that a formula is in prenex normal form.