What is the difference between a filter and deferred processing in programming?

Filtering and lazy evaluation are different concepts:

• Filtering is an operation that immediately applies a condition to data and returns only those elements that satisfy this condition. For example, in Python, filter() returns an iterator with filtered elements.

• Lazy evaluation is when computations are not performed immediately but are deferred until the result is actually needed. For example, generators in Python create elements one by one during iteration, not all at once.

Example:

# Filtering with lazy evaluation
nums = range(10)
filtered = filter(lambda x: x % 2 == 0, nums)  # filter returns an iterator

for num in filtered:
    print(num)  # elements are computed and output during iteration

Here, filtering and laziness work together: the filter sets the condition, and the generator/iterator provides deferred processing.