and(): Requiring Every Condition to Be True

and() combines logical conditions and returns true only when every supplied condition is true. It is the natural way to express rules with several requirements: and(age >= 18, age < 65) means that both limits must hold.

Truth tables in practice

The essential cases are simple: and(true, true) is true; any false argument makes the result false. This is ideal for validation, filtering, and guarded calculations. A denominator check can be written with and(denominator != 0, value is valid) before a divide() operation.

Use or() when any one of several alternatives is enough, and not() to reverse a condition. For comparing quantities, functions such as largerEq(), smaller(), and equal() create the boolean inputs that and combines.

Clear, safe conditions

Group related tests and name intermediate values when a condition grows long. For example, check an array’s size before extracting an element, and check numeric status with isNumeric() before applying a numerical formula. This makes error cases intentional rather than accidental.

Logical functions work with boolean values, not vague textual intent. Be explicit about comparisons and remember that equality tests on decimal results can be fragile because of floating-point rounding. When appropriate, compare a difference against a tolerance instead.