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);

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 }