def _ThreeArgs(argv):
"""Returns an expression tree to be evaluated."""
a0, a1, a2 = argv
# NOTE: Order is important here.
binary_id = _BINARY_LOOKUP.get(a1)
if binary_id is not None:
left = ast.StringWord(Id.Word_Compound, a0)
right = ast.StringWord(Id.Word_Compound, a2)
return ast.BoolBinary(binary_id, left, right)
if a1 == '-a':
left = _StringWordTest(a0)
right = _StringWordTest(a2)
return ast.LogicalAnd(left, right)
if a1 == '-o':
left = _StringWordTest(a0)
right = _StringWordTest(a2)
return ast.LogicalOr(left, right)
if a0 == '!':
child = _TwoArgs(argv[1:])
return ast.LogicalNot(child)
if a0 == '(' and a2 == ')':
return _StringWordTest(a1)
util.p_die('Syntax error: binary operator expected, got %r (3 args)', a1)
def ParseExpr(self):
"""
Iterative:
Expr : Term (OR Term)*
Right recursion:
Expr : Term (OR Expr)?
"""
left = self.ParseTerm()
# [[ uses || but [ uses -o
if self.op_id in (Id.Op_DPipe, Id.BoolUnary_o):
self._Next()
right = self.ParseExpr()
return ast.LogicalOr(left, right)
else:
return left
def ParseExpr(self):
"""
Iterative:
Expr : Term (OR Term)*
Right recursion:
Expr : Term (OR Expr)?
"""
left = self.ParseTerm()
if not left:
return None # TODO: An exception should handle this case.
# [[ uses || while [ uses -o
if self.op_id in (Id.Op_DPipe, Id.BoolUnary_o):
if not self._Next(): return None
right = self.ParseExpr()
if not right: return None
return ast.LogicalOr(left, right)
else:
return left