Problem: extracting elements on CAS mode

[compsystems]

Now inform:

Python compatibility enabled. List index will start at 0,
run index:=1 ... or 0 to disable Python compatibility.

index:=0; returns "[] index start 0"

M1:=[[1,2],
[3,4]];

M1(0,0) returns "Error: Invalid input" // ok
M1(1,1) returns 1 // ok
M1[0,0] returns input: M1[0,1] output [[1,2],[3,4]] // ?

index:=1; returns "[] index start 0"

M1:=[[1,2],
[3,4]];

M1(0,0) returns "Error: Invalid input"
M1(1,1) returns 1
M1[0,0] returns input: M1[-1, 0] output: [[1,2],[3,4]] // ?