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11.3.9 ask_query/4   hookable

Synopsis

ask_query(+QueryClass, +Query, +Help, -Answer)

Prints the question Query, then reads and processes user input according to QueryClass, and returns the result of the processing, the abstract answer term Answer. The Help message may be printed in case of invalid input.

Arguments

QueryClass

term, must be nonvar

Determines the allowed values for the atom Answer.

Query

term

A message term.

Help

term

A message term.

Answer

term

See QueryClass

Description

All queries made by the system are handled by calling this predicate.

First ask_query/4 calls query_hook/6 with the same arguments plus the Query and Help arguments converted to format-command lines. If this call succeeds, then it overrides all further processing done by ask_query/4. Otherwise, the query is processed in the following way:

Exceptions

instantiation_error

QueryClass, Query, or Help uninstantiated.

type_error

QueryClass not an atom.

domain_error

QueryClass not a valid query class.

See Also

Query Processing.



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