Category:CafeOBJ

CafeOBJ
This programming language may be used to instruct a computer to perform a task.

See Also:	CafeOBJ on the HOPL

Listed below are all of the tasks on Rosetta Code which have been solved using CafeOBJ.

Basic Information

CafeOBJ is a algebraic specification language. It has an executable sub-language which is broadly similar to Haskell or ML. CafeOBJ has many advanced features including: multiple logics, flexible mix-fix syntax, powerful and clear typing system with ordered sorts, parametric modules and views for instantiating the parameters, and module expressions, and more. CafeOBJ is primarily a first order specification language which can also be used as a functional programming language. Being first order, there are no higher order functions such as map. Higher order functions can be simulated to some degree using paramterized modules. CafeOBJ includes minimal library of basic types such as natural numbers, integers, floating point number, and character string. There are no libraries for arrays, lists, trees, or graphs, hence the user written list below. Many of CafeOBJ features are inherited from OBJ3

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Examples

<lang CafeOB> -- Text file called say Hello.cafe ,contains the following mod! HELLO-WORLD { pr(STRING) op hello : -> String eq hello = "Hello World" . } -- Start CafeOBJ interactive session at command line --> cafeobj -- Bring *in* the file at CafeOBJ prompt in hello.cafe -- Open the HELLO-WORLD module open HELLO-WORLD -- Execute with the reduce command reduce hello . -- Gives ("Hello World"):String </lang>

See [1] for more traditional quicksort

<lang CafeOB> -- Here is a one line sorting program. mod! SORTING-NAT { pr(NAT) [Nat < List ] -- Simple list structure op nil : -> List op _._ : List List -> List { assoc id: nil }

vars N N' : Nat -- A very short sorting program using one transition equation in POA logic, which is a type of rewrite logic. -- The program is in the form of a condition transition, which will swap N and N' if N is larger or equal to N'. -- This is a equation in POA logic so there is no need for an intermediate variable to do the swap. ctrans [swap] : (N . N') => (N' . N) if N' <= N . }

• • > Sorting natural numbers using exec command

open SORTING-NAT exec (3 . 2 . 1) . --> Gives (1 . 2 . 3):List

• • > We can consider sorting as a path through the state space of the permutations of N numbers.
  • > There are N! permutations only one of which is sorted.
  • > Sorting natural numbers using search command
  • > we can use (show path N) with this command, where N is the number of possible states.

red (3 . 2 . 1) =(1,1)=>* (1 . 2 . 3) . red (3 . 2 . 1) =(1,2)=>* (1 . 2 . 3) . red (3 . 2 . 1) =(1,3)=>* (1 . 2 . 3) .

• • > search for any number of solutions at any depth

red (3 . 2 . 1) =(*,*)=>* (1 . 2 . 3) .

• • > print the transitions from initial to goal state

show path 5 eof </lang>