Stck Language Spec

The Stck language is defined by the following specification.

Comments

Comments start with # and extend to the end of the line.

Primitives

Stck uses two primary data types.

• Numbers. e.x. -1, 1.2, 4, 0
• Strings. e.x. "hello"

Stacks

Stacks are the only data structure in stck. They are identified using a sequence of alpha characters. They can be pushed to or popped from.

• 1>a: Push value 1 onto stack a
• a>b: Pop from stack a and push value to stack b
• a>: Pop from stack a

Popping from an empty stack always returns 0.

There are two special stacks:

• Stack i is read only and contains the standard input.
• Stack o is write only. Values pushed to this stack are sent to standard output.

Operators

In addition to popping and pushing, stacks can be manipulated with operators.

Math: +, -, *, /

In the following examples, addition can be replaced with any of the mathematical operators.

Syntax: stack+operand or stack+stack or stack+

• a+b: Pop from a and b, perform addition, push the result to a.
• a+: Pop two values from a, perform addition, push the result to a.
• a+4: Pop from a, perform addition with the literal 4, push the result to a.

Clear: ?

Syntax: stack?

Clears the stack if the topmost value is 0.

Functions

Functions are defined between curly braces.

Syntax: {:name BODY}

{:name
  # function body
}

When a function is called, the function body is executed. Functions can only be defined at the top level of a program.

Loops

Loops are defined between parens

Syntax: (stack BODY)

(n
  # loop body
)

A loop will execute until the stack is empty.