def dpll_satisfiable(s):
    """Check satisfiability of a propositional sentence.
    This differs from the book code in two ways: (1) it returns a model
    rather than True when it succeeds; this is more useful. (2) The
    function find_pure_symbol is passed a list of unknown clauses, rather
    than a list of all clauses and the model; this is more efficient.
    >>> ppsubst(dpll_satisfiable(A&~B))
    {A: True, B: False}
    >>> dpll_satisfiable(P&~P)
    False
    """
    clauses = conjuncts(to_cnf(s))
    symbols = prop_symbols(s)
    return dpll(clauses, symbols, {})
def dpll_satisfiable(s):
    """Check satisfiability of a propositional sentence.
    This differs from the book code in two ways: (1) it returns a model
    rather than True when it succeeds; this is more useful. (2) The
    function find_pure_symbol is passed a list of unknown clauses, rather
    than a list of all clauses and the model; this is more efficient.
    >>> ppsubst(dpll_satisfiable(A&~B))
    {A: True, B: False}
    >>> dpll_satisfiable(P&~P)
    False
    """
    clauses = conjuncts(to_cnf(s))
    symbols = prop_symbols(s)
    return dpll(clauses, symbols, {})
def dpll_satisfiable ( s ) : clauses = conjuncts ( to_cnf ( s ) ) symbols = prop_symbols ( s ) return dpll ( clauses , symbols , { } )
Check satisfiability of a propositional sentence.
    This differs from the book code in two ways: (1) it returns a model
    rather than True when it succeeds; this is more useful. (2) The
    function find_pure_symbol is passed a list of unknown clauses, rather
    than a list of all clauses and the model; this is more efficient.
    >>> ppsubst(dpll_satisfiable(A&~B))
    {A: True, B: False}
    >>> dpll_satisfiable(P&~P)
    False
Check satisfiability of a propositional sentence . This differs from the book code in two ways : ( 1 ) it returns a model rather than True when it succeeds ; this is more useful . ( 2 ) The function find_pure_symbol is passed a list of unknown clauses rather than a list of all clauses and the model ; this is more efficient . >>> ppsubst ( dpll_satisfiable ( A&~B )) { A : True B : False } >>> dpll_satisfiable ( P&~P ) False