@hackage / d10

d10

Data types representing the digits zero through nine.

Modules

Each of the following modules defines a different type named D10, all of which are different representations of the same concept:

• D10.Char - Defines a D10 type as a newtype for Char, where the values are restricted to characters between '0' and '9'.
• D10.Num - Defines a D10 type as a newtype for any type with an instance of the Num class, where the values are restricted to numbers between fromInteger 0 and fromInteger 9.
• D10.Safe - Defines a D10 type as D0 | D1 | D2 | ... | D9.

Quasi-quoters

Each module that defines a D10 type also defines quasi-quoters for it. With the QuasiQuotes GHC extension enabled, a single digit like 7 can be written as [d10|7|], and a list of digits like [4,5,6] can be written as [d10|456|]. For D10.Char and D10.Num, the quasi-quoters are an important feature, because the D10 types defined in these modules have unsafe constructors, and the quasi-quoters provide compile-time assurance that we never construct a D10 that represents a value outside the range 0 to 9.