Programming > STUDY GUIDE > Simple logical inference system: resolution and model checking for first-order logic. CODE (All)

Simple logical inference system: resolution and model checking for first-order logic. CODE

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Simple logical inference system: resolution and model checking for first-order logic. # @author Percy Liang import collections # Recursively apply str inside map def rstr(x): if isinstance(x, tu ... ple): return str(tuple(map(rstr, x))) if isinstance(x, list): return str(map(rstr, x)) if isinstance(x, set): return str(set(map(rstr, x))) if isinstance(x, dict): newx = {} for k, v in x.items(): newx[rstr(k)] = rstr(v) return str(newx) return str(x) class Expression: # Helper functions used by subclasses. def ensureType(self, arg, wantedType): if not isinstance(arg, wantedType): raise Exception('%s: wanted %s, but got %s' % (self.__class__.__name__, wantedType, arg)) return arg def ensureFormula(self, arg): return self.ensureType(arg, Formula) def ensureFormulas(self, args): for arg in args: self.ensureFormula(arg) return args def isa(self, wantedType): return isinstance(self, wantedType) def join(self, args): return ','.join(str(arg) for arg in args) def __eq__(self, other): return str(self) == str(other) def __hash__(self): return hash(str(self)) # Cache the string to be more efficient def __repr__(self): if not self.strRepn: self.strRepn = self.computeStrRepn() return self.strRepn # A Formula represents a truth value. class Formula(Expression): pass # A Term coresponds to an object. class Term(Expression): pass # Variable symbol (must start with '$') # Example: $x class Variable(Term): def __init__(self, name): if not name.startswith('$'): raise Exception('Variable must start with "$", but got %s' % name) self.name = name self.strRepn = None def computeStrRepn(self): return self.name [Show More]

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