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3.7.2 Parameter list
Syntax:
( )
( parameter_definition )
Purpose:
-
Defines the number, type and names of the arguments of a procedure.
-
The parameter_list is optional.
-
Adding
list # as argument to a parameter list means to allow
optional parameters. Furthermore, (list #) is the default for a
parameter list (in case no list is explicitly given). Inside the procedure
body, the arguments of list # are referenced by #[1], #[2] ,
etc.
-
If a procedure has optional parameters, the attribute
default_arg
gives the default values for the optional arguments. This provides in
particular the possibility to also change the behaviour of all procedures
nested inside the given procedure.
Example:
| proc x0
{
// can be called with
... // any number of arguments of any type: #[1], #[2],...
// number of arguments: size(#)
}
proc x1 ()
{
... // can only be called without arguments
}
proc x2 (ideal i, int j)
{
... // can only be called with 2 arguments,
// which can be converted to ideal resp. int
}
proc x3 (i,j)
{
... // can only be called with 2 arguments
// of any type
// (i,j) is the same as (def i,def j)
}
proc x5 (i,list #)
{
... // can only be called with at least 1 argument
// number of arguments: size(#)+1
}
attrib(x5,"default_arg",3);
x5(2); // is equivalent to
x5(2,3);
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Note:
The parameter_list may stretch across multiple lines.
A parameter may have any type (including the types proc
and ring ).
If a parameter is of type ring, then it
can only be specified by name, but not with a type. For instance:
| proc x6 (r)
{
... // this is correct, r may be of any type, even of type ring
}
proc x7 (ring r)
{
... // this is NOT CORRECT
}
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