Rewriting Nested Conditionals as Boolean Expressions

A nested conditional checks one condition, and only if that passes, checks another. When the only job of that nest is to decide true or false, the nesting is just AND in disguise. An outer IF that leads to an inner IF, which returns true only when both pass, is logically identical to one line: condition A AND condition B. The program still checks both conditions, but you've erased the scaffolding and kept the logic.

The mechanism is to trace every path through the nest and ask what truth value it produces. If true only happens when A and B both happen, write A AND B. If true happens when A happens or B happens, write A OR B. A nest that returns true when a condition fails becomes NOT of that condition. Once every branch maps cleanly onto true or false, you can replace the whole structure with one expression built from AND, OR, and NOT, and a single IF with that expression as its test.

This matters for readability and for connecting conditionals to the Boolean logic used in searches, filters, and list operations elsewhere in the course. A short AND or OR expression is easier to verify than four lines of nested IF statements doing the same job. But collapsing has a limit: it only works when every branch of the nest is deciding the same true-or-false question. A nest that assigns three different grades, or returns three different strings, is choosing between outcomes, not between true and false, so there is no single Boolean expression that captures it.