Final answer:
Three concrete examples are given in Python, Modula-3, and Scheme, where a variable is live but not in scope. The examples demonstrate scenarios in which the variables are defined inside a function, block, or lambda expression and referenced outside of them.
Step-by-step explanation:
Example 1: Python
In Python, a variable can be live but not in scope if it is defined inside a function and referenced outside of that function. For example:
def my_function():
x = 5
my_function()
print(x)
In this code, the variable 'x' is defined inside 'my_function' and is not accessible outside of it. So when we try to print 'x' outside of the function, we get an error.
Example 2: Modula-3
In Modula-3, a variable can be live but not in scope if it is defined inside a block and referenced outside of that block. For example:
BEGIN
VAR y := 10;
END;
BEGIN
print(y);
END;
In this code, the variable 'y' is defined inside the first block and is not accessible outside of it. So when we try to print 'y' in the second block, we get an error.
Example 3: Scheme
In Scheme, a variable can be live but not in scope if it is defined inside a lambda expression and referenced outside of that expression. For example:
(define my-function
(lambda (z)
(let ((x 5))
(+ x z))))
(my-function 10)
(print x)
In this code, the variable 'x' is defined inside the lambda expression and is not accessible outside of it. So when we try to print 'x' after calling the 'my-function', we get an error.