51 lines
1.8 KiB
C
51 lines
1.8 KiB
C
/**
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* stack.h
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*
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* The Lisp evaluation stack.
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*
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* Stack frames could be implemented in cons space; indeed, the stack
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* could simply be an assoc list consed onto the front of the environment.
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* But such a stack would be costly to search. The design sketched here,
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* with stack frames as special objects, SHOULD be substantially more
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* efficient, but does imply we need to generalise the idea of cons pages
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* with freelists to a more general 'equal sized object pages', so that
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* allocating/freeing stack frames can be more efficient.
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*
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* Stack frames are not yet a first class object; they have no VECP pointer
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* in cons space.
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*
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* (c) 2017 Simon Brooke <simon@journeyman.cc>
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* Licensed under GPL version 2.0, or, at your option, any later version.
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*/
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#include "consspaceobject.h"
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#include "conspage.h"
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#ifndef __stack_h
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#define __stack_h
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struct stack_frame *make_stack_frame( struct stack_frame *previous,
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struct cons_pointer args,
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struct cons_pointer env );
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void free_stack_frame( struct stack_frame *frame );
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struct cons_pointer fetch_arg( struct stack_frame *frame, unsigned int n );
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/**
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* A 'special' frame is exactly like a normal stack frame except that the
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* arguments are unevaluated.
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* @param previous the previous stack frame;
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* @param args a list of the arguments to be stored in this stack frame;
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* @param env the execution environment;
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* @return a new special frame.
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*/
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struct stack_frame *make_special_frame( struct stack_frame *previous,
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struct cons_pointer args,
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struct cons_pointer env );
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/*
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* struct stack_frame is defined in consspaceobject.h to break circularity
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* TODO: refactor.
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*/
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#endif
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