Substitute operands of a domain element

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extsubsop(d, i1 = new1, i2 = new2, …)


extsubsop(d, i = new) returns a copy of the domain element d with the i-th operand of the internal representation replaced by new.

Internally, a domain element may consist of an arbitrary number of objects. extsubsop replaces one or more of these objects, without checking whether the substitution is meaningful.


The operands of elements of domains of the MuPAD® library must meet certain (undocumented) conditions; use extsubsop only for your own domains. It is good programming style to use extsubsop only inside low-level domain methods.

extsubsop returns a modified copy of the object, but does not change the object itself.

The numbering of operands is the same as the one used by extop.

If the 0-th operand is to be replaced, the corresponding new value must be a domain of type DOM_DOMAIN; extsubsop then replaces the domain of d by this new domain.

When trying to replace the i-th operand with i exceeding the actual number of operands, extsubsop first increases the number of operands by appending as many NIL's as necessary and then performs the substitution. Cf. Example 3.

When the i-th operand is replaced by an expression sequence of k elements, each of these elements becomes an individual operand of the result, indexed from i to i+k-1. The remaining operands of d are shifted to the right accordingly. This new numbering is already in effect for the remaining substitutions in the same call to extsubsop. Cf. Example 4.

The void object null() becomes an operand of the result when it is substituted into an object.

After performing the substitution, extsubsop does not evaluate the result once more. Cf. Example 5.

In contrast to the function subsop, extsubsop cannot be overloaded.

Like extop and extnops, extsubsop can be applied to objects of a kernel domain. In this case extsubsop behaves like subsop.


Example 1

We create a domain element and then replace its first operand:

d := newDomain("1st"): e := new(d, 1, 2, 3): extsubsop(e, 1 = 5)

This does not change the value of e:


delete d, e:

Example 2

The domain type of an element can be changed by replacing its 0-th operand:

d := newDomain("some_domain"): e := new(d, 2): 
extsubsop(e, 0 = Dom::IntegerMod(5))

delete d, e:

Example 3

We substitute the sixth operand of a domain element that has less than six operands. In such cases, an appropriate number of NIL's is inserted:

d := newDomain("example"): e := new(d, 1, 2, 3, 4):
extsubsop(e, 6 = 8)

delete d, e:

Example 4

We substitute the first operand of a domain element e by a sequence with three elements. These become the first three operands of the result; the second operand of e becomes the fourth operand of the result, and so on. This new numbering is already in effect when the second substitution is carried out:

d := newDomain("example"): e := new(d, 1, 2, 3, 4):
extsubsop(e, 1 = (11, 13, 17), 2 = (29, 99))

delete d, e:

Example 5

We define a domain with its own evaluation method. This method prints out its argument such that we can see whether it is called. Then we define an element of our domain.

d := newDomain("anotherExample"): 
d::evaluate := x -> (print("Argument:", x); x):
e := new(d, 3)

We can now watch all evaluations that happen: extsubsop evaluates its arguments, performs the desired substitution, but does not evaluate the result of the substitution:

extsubsop(e, 1 = 0)

delete d, e:

Example 6

extsubsop applied to an object from a kernel type yields the same result as subsop:

extsubsop([1,2,3], 2=4), subsop([1,2,3], 2=4)



Arbitrary MuPAD object

i1, i2, …

Nonnegative integers

new1, new2, …

Arbitrary MuPAD objects

Return Values

Input object with replaced operands.

See Also

MuPAD Domains

MuPAD Functions