Create a domain element
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new(T
, object1, object2, …
)
Within a method of the domain type T
, new(T,
object1, object2, ...)
creates a new element of the domain T
with
the internal representation object1, object2, ...
.
new
is a lowlevel function for creating
elements of library domains.
The internal representation of a domain element comprises a reference to the corresponding domain and an arbitrary number of MuPAD^{®} objects, the internal operands of the domain element.
new(T, object1, object2, ...)
creates a new
element of the domain T
, whose internal representation
is the sequence of operands object1, object2, ...
,
and returns this element.
new(T)
creates a new element of the domain T
,
whose internal representation is an empty sequence of operands.
Note:

New domains can be created via newDomain
.
You can access the operands of the internal representation of
a domain element via extop
,
which, in contrast to op
,
cannot be overloaded for
the domain. The function op
is
sometimes overloaded for a domain in order to hide the internal, technical
representation of an object and to provide a more user friendly and
intuitive interface.
Similarly, the function extnops
returns the number of operands
of a domain element in the internal representation, and extsubsop
modifies an
operand in the internal representation. These functions, in contrast
to the related functions nops
and subsop
, cannot be overloaded
for a domain.
You can write a constructor for your own domain T
by
providing a "new"
method. This method is invoked
whenever the user calls T(arg1, arg2, ...)
. This
is recommended since it provides a more elegant and intuitive user
interface than new
. The "new"
method
usually performs some argument checking and converts the arguments arg1,
arg2, ...
into the internal representation of the domain,
using new
(see Example 1).
We create a new domain Time
for representing
clock times. The internal representation of an object of this domain
has two operands: the hour and the minutes. Then we create a new domain
element for the time 12:45
:
Time := newDomain("Time"): a := new(Time, 12, 45)
The domain type of a
is Time
,
the number of operands is 2
, and the operands are 12
and 45
:
domtype(a), extnops(a)
extop(a)
We now implement a "new"
method for our new
domain Time
, permitting several input formats.
It expects either two integers, the hour and the minutes, or only
one integer that represents the minutes, or a rational number or a
floatingpoint number, implying that the integral part is the hour
and the fractional part represents a fraction of an hour corresponding
to the minutes, or no arguments, representing midnight. Additionally,
the procedure checks that the arguments are of the correct type:
Time::new := proc(HR = 0, MN = 0) local m; begin if args(0) = 2 and domtype(HR) = DOM_INT and domtype(MN) = DOM_INT then m := HR*60 + MN elif args(0) = 1 and domtype(HR) = DOM_INT then m := HR elif args(0) = 1 and domtype(HR) = DOM_RAT then m := trunc(float(HR))*60 + frac(float(HR))*60 elif args(0) = 1 and domtype(HR) = DOM_FLOAT then m := trunc(HR)*60 + frac(HR)*60 elif args(0) = 0 then m := 0 else error("wrong number or type of arguments") end_if; new(Time, trunc(m/60), trunc(m) mod 60) end_proc:
Now we can use this method to create new objects of the domain Time
,
either by calling Time::new
directly, or, preferably,
by using the equivalent but shorter call Time(...)
:
Time::new(12, 45), Time(12, 45), Time(12 + 3/4)
Time(), Time(8.25), Time(1/2)
In order to have a nicer output for objects of the domain Time
,
we also define a "print"
method (see the help page
for print
):
Time::print := proc(TM) begin expr2text(extop(TM, 1)) . ":" . stringlib::format(expr2text(extop(TM, 2)), 2, Right, "0") end_proc:
Time::new(12, 45), Time(12, 45), Time(12 + 3/4)
Time(), Time(8.25), Time(1/2)

A MuPAD domain 

Arbitrary MuPAD objects 
Element of the domain T
.