/usr/lib/swipl/library/http/http_parameters.pl
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 http_convert_parameter(+Options, +FieldName, +ValueIn, -ValueOut) is det
Conversion of an HTTP form value. First tries the multifile hook http:convert_parameter/3 and next the built-in checks.
Arguments:
Option- List as provided with the parameter
FieldName- Name of the HTTP field (for better message)
ValueIn- Atom value as received from HTTP layer
ValueOut- Possibly converted final value
Errors
- type_error(Type, Value)