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* __scm.h: Reformulated the architecture and compiler properties

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in terms of properties of scm_t_bits and SCM variables rather than
	in terms of c standard types.  This is since it is not known which
	of the standard types scm_t_bits and SCM variables will be defined
	to.
This commit is contained in:
Dirk Herrmann 2003-07-24 06:32:20 +00:00
parent d7850c8d68
commit 59c4bb82e3
2 changed files with 31 additions and 8 deletions
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8
libguile/ChangeLog
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@ -1,3 +1,11 @@
2003-07-24 Dirk Herrmann <D.Herrmann@tu-bs.de>
* __scm.h: Reformulated the architecture and compiler properties
in terms of properties of scm_t_bits and SCM variables rather than
in terms of c standard types. This is since it is not known which
of the standard types scm_t_bits and SCM variables will be defined
to.
2003-07-24 Kevin Ryde <user42@zip.com.au>
* numbers.c (scm_angle): Use scm_flo0 for non-negative inum, bignum

31
libguile/__scm.h
View file

@ -3,7 +3,7 @@
#ifndef SCM___SCM_H
#define SCM___SCM_H
/* Copyright (C) 1995,1996,1998,1999,2000,2001,2002, 2003 Free Software Foundation, Inc.
/* Copyright (C) 1995,1996,1998,1999,2000,2001,2002,2003 Free Software Foundation, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@ -306,17 +306,32 @@
*
* Guile as of today can only work on systems which fulfill at least the
* following requirements:
* - long ints have at least 32 bits.
*
* - scm_t_bits and SCM variables have at least 32 bits.
* Guile's type system is based on this assumption.
* - long ints consist of at least four characters.
* It is assumed that cells, i. e. pairs of long ints, are eight character
* aligned, because three bits of a cell pointer are used for type data.
* - sizeof (void*) == sizeof (long int)
* Pointers are stored in SCM objects, and sometimes SCM objects are passed
* as void*. Thus, there has to be a one-to-one correspondence.
*
* - sizeof (scm_t_bits) >= sizeof (void*) and sizeof (SCM) >= sizeof (void*)
* Guile's type system is based on this assumption, since it must be
* possible to store pointers to cells on the heap in scm_t_bits and SCM
* variables.
*
* - sizeof (scm_t_bits) >= 4 and sizeof (scm_t_bits) is a power of 2.
* Guile's type system is based on this assumption. In particular, it is
* assumed that cells, i. e. pairs of scm_t_bits variables, are eight
* character aligned. This is because three bits of a scm_t_bits variable
* that is holding a pointer to a cell on the heap must be available for
* storing type data.
*
* - sizeof (scm_t_bits) <= sizeof (void*) and sizeof (SCM) <= sizeof (void*)
* In some parts of guile, scm_t_bits and SCM variables are passed to
* functions as void* arguments. Together with the requirement above, this
* requires a one-to-one correspondence between the size of a void* and the
* sizes of scm_t_bits and SCM variables.
*
* - numbers are encoded using two's complement.
* The implementation of the bitwise scheme level operations is based on
* this assumption.
*
* - ... add more
*/