Cayenne (programming language)

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Cayenne is a functional programming language with dependent types. The basic types are functions, products, and sums. Functions and products use dependent types to gain additional power.

There are very few building blocks in the language, but a lot of syntactic sugar to make it more readable. The syntax is largely borrowed from Haskell.

There is no special module system, because with dependent types records (products) are powerful enough to define modules.

The main aim with Cayenne is not to use the types to express specifications (although this can be done), but rather to use the type system to give type to more functions. An example of a function that can be given a type in Cayenne is printf.

PrintfType :: String -> #
PrintfType (Nil)          = String
PrintfType ('%':('d':cs)) = Int    -> PrintfType cs
PrintfType ('%':('s':cs)) = String -> PrintfType cs
PrintfType ('%':( _ :cs)) =           PrintfType cs
PrintfType ( _ :cs)       =           PrintfType cs
 
aux :: (fmt::String) -> String -> PrintfType fmt
aux  (Nil)          out = out
aux  ('%':('d':cs)) out = \ (i::Int)    -> aux  cs (out ++ show i)
aux  ('%':('s':cs)) out = \ (s::String) -> aux  cs (out ++ s)
aux  ('%':( c :cs)) out =                  aux  cs (out ++ c : Nil)
aux  (c:cs)         out =                  aux  cs (out ++ c : Nil)
 
printf :: (fmt::String) -> PrintfType fmt
printf fmt = aux fmt Nil

The Cayenne implementation is written in Haskell, and it also translates to Haskell.

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