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Writing Form Handlers in LP/CLP

• Use same techniques as with standard CGI apps.
• Only complication is form data parsing (names/values).
• Good solution: implement a parser (easy in LP/CLP) and produce an attribute-value pair list or dictionary.
• Enables the symbolic treatment of form data, hiding the low-level protocol behind.

E.g., predicates provided in PiLLoW:

• get_form_input(Dic) Translates input from the form to a dictionary Dic of attribute=value pairs. This is implemented using a simple DCG parser.
  get_form_input(Dict) Dict = [name='Anna', age=23]
• get_form_value(Dic,Var,Val) Gets value Val for attribute Var in dictionary Dic.
• form_empty_value(V) Useful to check that a value V from a text area is empty.
• my_url(URL) Returns in URL the Uniform Resource Locator (WWW address) of this form.

A browser can be used as a graphical interface!