minBound

minBound is a polymorphic constant used in Haskell to refer to the smallest value representable by a type that implements the Bounded type class. Along with maxBound, minBound defines the lower bound of a bounded type. Bounded is intended for types with a well-defined finite range, such as Bool, Char, and fixed-size numeric types. Types like Integer are not instances of Bounded because they are unbounded.

In practice, minBound is accessed at a type annotation, for example minBound :: Int yields the smallest Int value on the current machine, and minBound :: Bool yields False. For Char, minBound returns the smallest Char representable in the underlying implementation.

minBound is commonly used when initializing variables, constructing ranges, or iterating over all values of a bounded type. When a type also implements Enum, you can enumerate all values with [minBound..maxBound], for example to produce a list of all colors defined by a bounded, enumerable type.

Custom data types can derive Bounded and Enum to gain minBound and maxBound automatically. For instance: data Color = Red | Green | Blue deriving (Bounded, Enum, Show) yields minBound = Red and maxBound = Blue.

Notes: minBound is not a function, but a constant defined per type. Its exact representation differs by type: for numeric types it is the smallest representable value (architecture-dependent for signed ints), while for Bool and Char it is fixed by their standard definitions.