| unroll |
(Pointer source [, Pointer dest]) |
reserved |
| |
|
Copies elements from
source
into
dest,
or a new array if
dest
is omitted, and returns the destination (i.e., either
dest
or the new array) to the caller.
When an object, like a dictionary, that associates names with values
is unrolled into an object, like an array that does not, then
unroll
includes the name and the value of each element in the destination.
Something special happens when
unroll
is used as an argument in a function call or one of the comma separated expressions,
enclosed in braces, that can be used to initialize arrays and dictionaries.
The Yoix interpreter notices that the object was returned by
unroll
and decides that the individual elements in that object that are also initialized,
rather than the object itself, should be the arguments in the function call or the
elements in the initializer.
Although it is may not be obvious, these really are
unroll's
most important uses.
| |
| Example: |
The program,
import yoix.stdio.*;
f(Stream stream, String fmt, ...) {
if (stream == stdout)
printf(unroll(&fmt));
else fprintf(unroll(&stream));
}
f(stdout, "this calls %s\n", "printf");
f(stderr, "this calls %s\n", "fprintf");
prints
this calls printf
on standard output and
this calls fprintf
on standard error.
Even though it is a trivial example it illustrates how
unroll
can be used when you are in a function, often one with a
variable argument list, and you want to call another function,
once again often one with a variable argument list.
Right now dictionaries, arrays, and strings can be quickly and easily
duplicated using simple declarations, so
Dictionary dict[] = VM;
makes a copy of the
VM
dictionary and
String str[] = VM.Created;
makes a copy the
VM.Created
string.
The square brackets are the key that tell the interpreter we want to make
a copy, but unfortunately they currently don't work with objects, like a
Point
or
Rectangle,
that associate names with values but are not dictionaries.
However
unroll
does work, so the program
import yoix.*.*;
Point p1 = {
double x = 123.456;
double y = 654.321;
};
Point p2 = {unroll(p1)};
printf("p2=%O\n", p2);
prints
p2=Point[2:0]
>x=123.456
y=654.321
on standard output.
| | |
| Return: |
Pointer
|
|
Yoix is a registered trademark of AT&T Inc.
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