6.40.7 Modifying the elements of a list: subsop
The subsop command can be used to
modify elements in a list.
-
subsop takes two arguments:
-
L, a list.
- i=value, an index and a new value.
- (In all but Maple mode).
subsop(L,i=value) returns the list L
with the value at index i replaced by value.
- (In Maple mode; the only difference is the order of
the arguments).
subsop(i=value,L) returns the list L
with the value at index i replaced by value.
Remark: If the second argument is i=NULL, then
the element at index i is removed from L.
You can also redefine elements (or define new elements, but not remove
elements) with :=.
Examples.
-
Input (in Xcas mode, the index of the first element is 0):
subsop([0,1,2],1=5)
or:
L:=[0,1,2];L[1]:=5
Output:
- Input (in Xcas mode, the index of the first element is 0):
subsop([0,1,2],’1=NULL’)
Output:
- Input (in Mupad TI mode, the index of the first element is 1):
subsop([0,1,2],2=5)
or:
L:=[0,1,2];L[2]:=5
Output:
- When using := to insert an element in a list, the list will
be padded with 0s if necessary.
Input:
L:=[]
then:
L[3]:=5
Output:
- In Maple mode the arguments are permuted and the index of
the first element is 1.
Input:
subsop(2=5,[0,1,2])
or:
L:=[0,1,2];L[2]:=5
Output: