IS Operator for IS BLANK or IS NOT BLANK

[jheth]

I would like support for an "IS operator where I can do "IS BLANK" or "IS NOT BLANK" to see if a particular value exists or not. In my own expression evaluator I'm using Object#blank? and Object#present? from Rails to check this condition.

Is this something you'd be willing to add or accept a PR for?

[rubysolo]

The language is roughly modeled around the Excel formula language, so I would expect it to look more like TRIM(variable) = '' or BLANK(variable) or IS_BLANK(variable). I would consider one of these as a PR.

[jheth]

Thanks. Good to know. I like the IS_BLANK(variable) syntax. I'll give that a try. I was originally using SQL-like syntax so the expression could be used against a hash or a database.

[jheth]

This is my test function for testing an empty variable but it doesn't accept nil values. I'm using the :non_group signature to accept any type of variable but it's not accepting nil.

c.add_function(
    name: :blank,
    type: :logical,
    signature: [:non_group],
    body: ->(var) {
      return (var.to_s.strip.empty?)
    }
  )

c.evaluate("BLANK(0)")
 => false 

c.evaluate("BLANK(12345)")
 => false 

c.evaluate("BLANK('   ')")
 => true

c.evaluate("BLANK(nil)")
 => nil 

[rubysolo]

nil isn't a keyword inside Dentaku, so you'd probably have to set a variable to nil and pass that in:

c.evaluate("BLANK(foo)", foo: nil)