Reorganised source files to make navigation easier

All tests still pass (slightly to my surprise)

src/memory/stack.h

@@ -0,0 +1,75 @@
+/**
+ * stack.h
+ *
+ * The Lisp evaluation stack.
+ *
+ * Stack frames could be implemented in cons space; indeed, the stack
+ * could simply be an assoc list consed onto the front of the environment.
+ * But such a stack would be costly to search. The design sketched here,
+ * with stack frames as special objects, SHOULD be substantially more
+ * efficient, but does imply we need to generalise the idea of cons pages
+ * with freelists to a more general 'equal sized object pages', so that
+ * allocating/freeing stack frames can be more efficient.
+ *
+ * Stack frames are not yet a first class object; they have no VECP pointer
+ * in cons space.
+ *
+ * (c) 2017 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include "consspaceobject.h"
+#include "conspage.h"
+
+#ifndef __stack_h
+#define __stack_h
+
+/**
+ * set a register in a stack frame. Alwaye use this macro to do so,
+ • because that way we can be sure the inc_ref happens!
+ */
+#define set_reg(frame,register,value)frame->arg[register]=value; inc_ref(value)
+
+
+/**
+ * Make an empty stack frame, and return it.
+ * @param previous the current top-of-stack;
+ * @param env the environment in which evaluation happens.
+ * @return the new frame.
+ */
+struct stack_frame *make_empty_frame( struct stack_frame *previous,
+                                      struct cons_pointer env );
+
+struct stack_frame *make_stack_frame( struct stack_frame *previous,
+                                      struct cons_pointer args,
+                                      struct cons_pointer env,
+                                      struct cons_pointer *exception );
+void free_stack_frame( struct stack_frame *frame );
+
+/**
+ * Dump a stackframe to this stream for debugging
+ * @param output the stream
+ * @param frame the frame
+ */
+void dump_frame( FILE * output, struct stack_frame *frame );
+
+struct cons_pointer fetch_arg( struct stack_frame *frame, unsigned int n );
+
+/**
+ * A 'special' frame is exactly like a normal stack frame except that the
+ * arguments are unevaluated.
+ * @param previous the previous stack frame;
+ * @param args a list of the arguments to be stored in this stack frame;
+ * @param env the execution environment;
+ * @return a new special frame.
+ */
+struct stack_frame *make_special_frame( struct stack_frame *previous,
+                                        struct cons_pointer args,
+                                        struct cons_pointer env );
+
+/*
+ * struct stack_frame is defined in consspaceobject.h to break circularity
+ * TODO: refactor.
+ */
+
+#endif