Curry

Curry, short for Curry Programming Language, was created by Michael Hanus in 1995. Curry is a functional logic programming language that combines features of Haskell and logic programming paradigms to enable declarative programming with lazy evaluation, higher-order functions, and non-deterministic search. Developers can access Curry through the official site: Curry Downloads, which provides compilers, libraries, and documentation for Windows, macOS, and Linux platforms.

Curry exists to provide a unifying language that merges functional and logic programming concepts. Its design philosophy emphasizes declarativity, expressiveness, and correctness. By integrating non-deterministic computations and higher-order functions, Curry solves the problem of writing concise, high-level code for symbolic computation, theorem proving, and AI applications while maintaining clarity and composability.

Curry: Variables and Types

Curry features a strong static type system with type inference and supports polymorphic and algebraic data types.

-- Defining simple variables
name :: String
name = "Curry"

age :: Int
age = 25

numbers :: [Int]
numbers = [1, 2, 3, 4, 5]

main :: IO ()
main = putStrLn ("Language: " ++ name ++ ", Age: " ++ show age)

Variables in Curry are immutable by default. The type system allows safe composition of functions and data structures, similar to Haskell and OCaml.

Curry: Functions and Pattern Matching

Curry supports first-class functions and pattern matching for concise control flow and declarative computation.

square :: Int -> Int
square x = x * x

describeNumber :: Int -> String
describeNumber 0 = "zero"
describeNumber 1 = "one"
describeNumber _ = "other"

main = putStrLn ("Square of 5: " ++ show (square 5))

Pattern matching allows clean handling of multiple cases. Higher-order functions and declarative expressions in Curry are conceptually similar to Haskell and ML.

Curry: Non-Determinism and Logic Programming

Curry integrates non-deterministic search and logic variables, allowing declarative exploration of multiple solutions.

-- Example using logic variables
import Control.Monad.Search

findPair :: [Int] -> [Int] -> [(Int, Int)]
findPair xs ys = do
x <- xs
y <- ys
if x + y == 5 then return (x, y) else []

main = print (findPair [1,2,3] [2,3,4])

Non-deterministic computation allows exploring multiple possibilities automatically. This approach is analogous to logic programming in Prolog and functional paradigms in Haskell.

Curry: Modules and Libraries

Curry supports modular programming with separate modules and reusable libraries.

module MathOps where

add :: Int -> Int -> Int
add x y = x + y

sub :: Int -> Int -> Int
sub x y = x - y

main :: IO ()
main = print (add 3 5)

Modules encapsulate functions and data, promoting reusability and composability. This modular approach is similar to structures and functors in ML and namespaces in C++.

Curry is used for declarative programming, symbolic computation, theorem proving, and AI research. Its combination of functional and logic programming paradigms allows concise, expressive, and correct code. When used alongside Haskell, ML, and Prolog, Curry provides a robust environment for high-level, declarative software development.