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Distinguish #f and ().

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* __scm.h: #undef SICP.
* pairs.h (SCM_EOL): Delete this definition, equating it with
SCM_BOOL_F.
* tags.h (SCM_EOL): Give it a new definition here; I think I found
the value it used to have.  Doc fixes, too.
This commit is contained in:
Jim Blandy 1996-10-03 05:02:36 +00:00
parent ee81f9ca7b
commit 3c205827ce
3 changed files with 20 additions and 18 deletions
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7
libguile/__scm.h
View file

@ -95,12 +95,15 @@
/* {Unsupported Options}
*
* These must be defined.
* These must be defined as given here.
*/
#define CCLO
#define SICP
/* Guile Scheme supports the #f/() distinction; Guile Lisp won't. We
have horrible plans for their unification. */
#undef SICP

1
libguile/pairs.h
View file

@ -89,7 +89,6 @@ typedef SCM huge *SCMPTR;
#define SCM_PTR_LE(x, y) (!SCM_PTR_GT(x, y))
#define SCM_PTR_GE(x, y) (!SCM_PTR_LT(x, y))
#define SCM_EOL SCM_BOOL_F
#define SCM_NULLP(x) (SCM_EOL == (x))
#define SCM_NNULLP(x) (SCM_EOL != (x))

30
libguile/tags.h
View file

@ -80,27 +80,27 @@ typedef long SCM;
*
* Immediates -- meaning that the variable contains an entire Scheme object.
*
* Non-immediates -- meaning that the variable holds a (possibly tagged) pointer
* into the cons pair heap.
* Non-immediates -- meaning that the variable holds a (possibly
* tagged) pointer into the cons pair heap.
*
* Non-objects are distinguished from other values by careful coding only (i.e.,
* programmers must keep track of any SCM variables they create that don't contain
* ordinary scheme values).
* Non-objects are distinguished from other values by careful coding
* only (i.e., programmers must keep track of any SCM variables they
* create that don't contain ordinary scheme values).
*
* All immediates and non-immediates must have a 0 in bit 0. Only non-object
* values can have a 1 in bit 0. In some cases, bit 0 of a word in the heap
* is used for the GC tag so during garbage collection, that bit might be 1
* even in an immediate or non-immediate value. In other cases, bit 0 of a word
* in the heap is used to tag a pointer to a GLOC (VM global variable address)
* or the header of a struct. But whenever an SCM variable holds a normal Scheme
* value, bit 0 is 0.
* All immediates and non-immediates must have a 0 in bit 0. Only
* non-object values can have a 1 in bit 0. In some cases, bit 0 of a
* word in the heap is used for the GC tag so during garbage
* collection, that bit might be 1 even in an immediate or
* non-immediate value. In other cases, bit 0 of a word in the heap
* is used to tag a pointer to a GLOC (VM global variable address) or
* the header of a struct. But whenever an SCM variable holds a
* normal Scheme value, bit 0 is 0.
*
* Immediates and non-immediates are distinguished by bits two and four.
* Immediate values must have a 1 in at least one of those bits. Does
* this (or any other detail of tagging) seem arbitrary? Try changing it!
* (Not always impossible but it is fair to say that many details of tags
* are mutually dependent).
*/
* are mutually dependent). */
#define SCM_IMP(x) (6 & (int)(x))
#define SCM_NIMP(x) (!SCM_IMP(x))
@ -464,7 +464,7 @@ enum scm_tags
#define SCM_BOOL_T SCM_MAKIFLAG(17)
#define SCM_UNDEFINED SCM_MAKIFLAG(18)
#define SCM_EOF_VAL SCM_MAKIFLAG(19)
#define SCM_UNUSED_NIL_VALUE SCM_MAKIFLAG(20)
#define SCM_EOL SCM_MAKIFLAG(20)
#define SCM_UNSPECIFIED SCM_MAKIFLAG(21)