Cat is a stack based functional language inspired by the Joy programming language Like Joy, Cat is a cross between Forth and the FP language.

A prototype Cat interpreter, has been released into the public domain, and is available for download with C# source code at http://www.cdiggins.com/cat.zip.

Characteristics of Cat

Cat has no variables, no arguments, no constants, and no side-effects. Every Cat program takes a single stack as input, and returns a single stack as output. A Cat program is made up of a sequence of sub-programs. A sub-program may be user-defined or atomic programs.

A Nip of Cat

In Cat every operation, program, and literal, is a stack transform function. It takes a stack and returns a new stack. The following are examples of Cat programs:

    42; // pushes 42 onto the stack
    1 2; // pushes the value 1 and then the value 2 onto the stack
    1 2 swap; // pushes 2 and then 1 onto the stack.
    1 2 +; // pushes 3 onto the stack
    1 + 2; // increments the top value of the stack, then pushes 2 onto the stack
    pop; // removes the top item of the stack
    dup; // duplicates the top item on the stack
    [1 2 3]; // pushes a list of functions onto the stack
    [1 2 3] $; // pushes a list of values onto the stack
    [] 1 cons; // pushes a list containing the "1" function
  

for (int i=0; i < a.length; ++i)
{
  a[i] = DoSomeThing();
}

a.Map(DoSomething);