|  |  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 oflist #are referenced by#[1], #[2],
etc.
If a procedure has optional parameters, the attribute default_arggives 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);
 | 
Note:The parameter_list may stretch across multiple lines.
 A parameter may have any type (including the types
 procandring).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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