A more thorough explanation:

Definition: Purposive construction is the process of interpreting a written law or document by looking at its intended purpose. This means that the interpreter tries to understand what the authors of the law or document meant when they wrote it, and how it should be applied to a given situation.

Example: Let's say there is a law that prohibits the sale of alcohol to minors. If a store owner is caught selling alcohol to someone who is under 21 years old, the law would apply to them. However, if the store owner can prove that they believed the person was over 21, even if they were actually under 21, the law may not apply to them. This is because the purpose of the law is to prevent minors from obtaining alcohol, not to punish store owners who make an honest mistake.

This example illustrates how purposive construction can be used to interpret a law in a way that aligns with its intended purpose. By looking at the purpose of the law, the interpreter can determine whether or not it applies to a given situation, even if the literal wording of the law may suggest otherwise.