func (this *NNF) VisitFunction(expr expression.Function) (interface{}, error) {
var exp expression.Expression = expr
switch expr := expr.(type) {
case *expression.IsBoolean:
exp = expression.NewLE(expr.Operand(), expression.TRUE_EXPR)
case *expression.IsNumber:
exp = expression.NewAnd(
expression.NewGT(expr.Operand(), expression.TRUE_EXPR),
expression.NewLT(expr.Operand(), expression.EMPTY_STRING_EXPR))
case *expression.IsString:
exp = expression.NewAnd(
expression.NewGE(expr.Operand(), expression.EMPTY_STRING_EXPR),
expression.NewLT(expr.Operand(), expression.EMPTY_ARRAY_EXPR))
case *expression.IsArray:
exp = expression.NewAnd(
expression.NewGE(expr.Operand(), expression.EMPTY_ARRAY_EXPR),
expression.NewLT(expr.Operand(), _EMPTY_OBJECT_EXPR))
case *expression.IsObject:
// Not equivalent to IS OBJECT. Includes BINARY values.
exp = expression.NewGE(expr.Operand(), _EMPTY_OBJECT_EXPR)
}
return exp, exp.MapChildren(this)
}
