# prelude-edsl: An EDSL-motivated subset of the Prelude

[ bsd3, language, library ] [ Propose Tags ]

Prelude.EDSL exports a small subset of the Prelude: some standard types and classes plus a small number of convenience functions.

The motivation for this module is that it is common for deeply embedded domain-specific languages (EDSLs) to redefine identifiers from the Prelude, so EDSL users must hide the Prelude in their programs. However, there are certain useful things from the Prelude that are usually not redefined -- function composition being one example -- so it becomes quite awkward to have to hide everything from the Prelude.

The reason for exporting e.g the Num class but not Ord is that it is possible to give an instance for deep embeddings of the former but not the latter. For example, assuming Exp is the type of a deep embedding, we can have

(+) :: Exp -> Exp -> Exp

but not

(<) :: Exp -> Exp -> Exp

(because (<) has a Bool result, regardless of the type of the arguments).

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