The documentation uses a notation to show how the stack is modified when
a calculator operation is evaluated. The following is an example of the
notation to indicate that an operation consumes two BigInt values from
the stack and pushes one BigInt value back to the stack:
( BigInt BigInt -- BigInt )
Stack notation is enclosed by parenthesis (), items consumed from the
stack are to the left of --, and items produced to the stack are on the
right of --. The top of the stack is the right-most element.
An operation that consumes no values from the stack is notated as:
( -- BigInt )
An operation that produces no values to the stack is notated as:
( BigInt -- )
An operation that does not modify the stack is shown by:
( -- )
Parameters can be named by placing a name and a : before the type:
( real:Float imag:Float -- Complex )
If a parameter doesn't have a meaningful name, it may use names such
as p0, p1, etc. depending on its location on the stack:
( p0:BigInt p1:BigInt -- BigInt )
If an operation returns more than one value, the values may be also be named:
( x1:Float y1:Float -- x2:Float y2:Float )
When a there is a name that is the same on both sides of the --, that
indicates that the operation does not change the value. In the following
example, the y value is changed but the x value is not:
( x:Float y1:Float -- x:Float y2:Float )
A suffix of * is used when the parameter consumes the remaining elements of
the stack. if any. For example, the stack notation for the sum operation for
Decimal values is:
( Decimal* -- Decimal )
When a * suffix appears on a return type, that value can be found any number
of times. For example, the stack notation for the repeat operation is:
( expr:Val n:Int -- Val* )