PUSH variable-name,integer-expression

Inserts a new element into an array at the given index, shifting existing elements at that index and above up by one place to make room.
The inserted element is initialised to 0 (for integer and real arrays) or "" (for string arrays).

Remarks: Arrays are zero-indexed and range-checked.; Valid indices are 0 to size-1. An out-of-range index raises a runtime error.; PUSH does not change the array’s size. The element that was previously at index size-1 is discarded.; If you want to grow the array, call REDIM first.

How it works

Before: A(0) .. A(size-2), A(size-1)
PUSH A, i:
- Elements i .. size-2 move to i+1 .. size-1
- A(i) becomes 0 or ""
- The old A(size-1) is lost

Time cost is proportional to the number of elements moved.

Common patterns

Insert a value at a position
Use PUSH to make room, then assign into the cleared slot.

DIM A,5
A(0) = 10
A(1) = 20
A(2) = 30
A(3) = 40
A(4) = 50
 
PUSH A,2            REM make room at index 2
A(2) = 999          REM set the inserted element

Insert at the front (index 0)

DIM Q,4
Q(0) = 1
Q(1) = 2
Q(2) = 3
Q(3) = 4
 
PUSH Q,0
Q(0) = 100

Insert at the end position (index size-1)
This clears the last slot without moving others.

DIM B,3
B(0) = 7
B(1) = 8
B(2) = 9
 
PUSH B,2
B(2) = 99

Grow then insert without losing data

DIM N,3
N(0) = 1
N(1) = 2
N(2) = 3
 
REDIM N,4           REM make space for one more element
PUSH N,1            REM shift from index 1 upward
N(1) = 20           REM write inserted value

Strings

DIM NAMES$,4
NAMES$(0) = "ALPHA"
NAMES$(1) = "BETA"
NAMES$(2) = "GAMMA"
NAMES$(3) = "DELTA"
 
PUSH NAMES$,2
NAMES$(2) = "OMEGA"

Notes

Works with integer, real, and string arrays; the inserted default is 0 or "" accordingly.
Inserting at size-1 does not shift any values; it simply clears that last position.
If you need to insert multiple elements, consider calling REDIM once to grow the array, then perform several PUSH operations.

See also:
POP · REDIM · DIM