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5.21.5 Capturing the Stack or Innermost Stack Frame

When an error occurs in a running program, or the program hits a breakpoint, its state at that point can be represented by a stack of all the evaluations and procedure applications that are logically in progress at that time, each of which is known as a frame. The programmer can learn more about the program's state at the point of interruption or error by inspecting the stack and its frames.

— Scheme Procedure: make-stack obj . args
— C Function: scm_make_stack (obj, args)

Create a new stack. If obj is #t, the current evaluation stack is used for creating the stack frames, otherwise the frames are taken from obj (which must be either a debug object or a continuation).

args should be a list containing any combination of integer, procedure and #t values.

These values specify various ways of cutting away uninteresting stack frames from the top and bottom of the stack that make-stack returns. They come in pairs like this: (inner_cut_1 outer_cut_1 inner_cut_2 outer_cut_2 ...).

Each inner_cut_N can be #t, an integer, or a procedure. #t means to cut away all frames up to but excluding the first user module frame. An integer means to cut away exactly that number of frames. A procedure means to cut away all frames up to but excluding the application frame whose procedure matches the specified one.

Each outer_cut_N can be an integer or a procedure. An integer means to cut away that number of frames. A procedure means to cut away frames down to but excluding the application frame whose procedure matches the specified one.

If the outer_cut_N of the last pair is missing, it is taken as 0.

— Scheme Procedure: last-stack-frame obj
— C Function: scm_last_stack_frame (obj)

Return a stack which consists of a single frame, which is the last stack frame for obj. obj must be either a debug object or a continuation.