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Transcript
244 • 6 Procedures
The following example illustrates these behaviors:
> Indexed := proc( { `name[1]`::string := "hello",
`name[2]`::string := "goodbye" } )
sprintf("name[1]=\"%s\" -- name[2]=\"%s\"",`name[1]`,`name[2]`)
end proc:
> Indexed(name[1]="hi");
(6.59)
> Indexed(name[1]="bonjour",name[2]="aurevoir");
(6.60)
> Indexed(name[1,2]="good day");
(6.61)
> Indexed(name[2]=42);
Error, invalid input: Indexed expects value for keyword parameter
`name[2]` to be of type string, but received 42
The Special Case of evaln and uneval Modifiers
There is one case in which the first stage of argument processing is not keyword matching.
If the procedure was declared with any parameter(s) having an uneval or evaln modifier,
arguments are first assigned to positional parameters from left to right until the rightmost
uneval or evaln parameter has been bound to an argument or until all the arguments have
been exhausted, whichever happens first. For each argument/parameter pair:
If the parameter has no parameterType, the argument matches trivially, and becomes the
value for that parameter.
If the parameter has a parameterType specification, the argument may or may not match.
If it matches, the argument becomes the value for that parameter. If it does not match, an
exception is raised.
> Accumulate := proc( r::evaln(numeric), n::numeric,
{ operation::symbol := `+` } )
r := operation(eval(r),n)
end proc:
> total := 0:
> Accumulate(total, 2.3);
(6.62)
