This function returns the length of a formula (parentheses and spaces are ignored).
Useful for proofs by induction on the length of a propositional formula.

sage: f = propcalc.formula("a")
sage: len(f)
1
sage: g = propcalc.formula("a|b")
sage: len(g)
3

Component: symbolics

Keywords: logic, symbolics, propositional formula

Author: Medha Sharma, Dave Morris

Branch: 8e331fa

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/28053