### 18.2 Low Level Debug Functions

Use the following functions to directly access GCL stacks.

    (SI:VS i)	Returns the i-th entity in VS.
    (SI:IHS-VS i)	Returns the VS index of the i-th entity in IHS.
    (SI:IHS-FUN i)	Returns the function of the i-th entity in IHS.
    (SI:FRS-VS i)	Returns the VS index of the i-th entity in FRS.
    (SI:FRS-BDS i)	Returns the BDS index of the i-th entity in FRS.
    (SI:FRS-IHS i)	Returns the IHS index of the i-th entity in FRS.
    (SI:BDS-VAR i)	Returns the symbol of the i-th entity in BDS.
    (SI:BDS-VAL i)	Returns the value of the i-th entity in BDS.

    (SI:SUPER-GO i tag)
    	Jumps to the specified tag established by the TAGBODY frame at
    	FRS[i].  Both arguments are evaluated.  If FRS[i] happens to be
    	a non-TAGBODY frame, then (THROW (SI:IHS-TAG i) (VALUES)) is
    	performed.