* Cleaned up some limits-definitions.

libguile/ChangeLog

@@ -1,3 +1,18 @@
+2001-01-18  Dirk Herrmann  <D.Herrmann@tu-bs.de>
+
+	* __scm.h:  Added comment about architecture and compiler
+	properties that are required by guile.
+
+	(SCM_FIXNUM_BIT, SCM_MOST_POSITIVE_FIXNUM,
+	SCM_MOST_NEGATIVE_FIXNUM):  Moved to numbers.h.
+
+	(SCM_CHAR_BIT, SCM_LONG_BIT):  Moved here from numbers.h.
+
+	* numbers.h (SCM_CHAR_BIT, SCM_LONG_BIT):  Moved to __scm.h.
+
+	(SCM_FIXNUM_BIT, SCM_MOST_POSITIVE_FIXNUM,
+	SCM_MOST_NEGATIVE_FIXNUM):  Moved here from __scm.h.
+
 2001-01-17  Dirk Herrmann  <D.Herrmann@tu-bs.de>
 
 	* __scm.h (SCM_FIXNUM_BIT):  Added.  The name is chosen in analogy

libguile/__scm.h

@@ -203,37 +203,46 @@ typedef unsigned long long ulong_long;
 
 
 
-/* Define
+/* {Architecture and compiler properties}
  *
- * SCM_CHAR_CODE_LIMIT		== UCHAR_MAX + 1
+ * Guile as of today can only work on systems which fulfill at least the
- * SCM_MOST_POSITIVE_FIXNUM 	(LONG_MAX>>2)
+ * following requirements:
- * SCM_MOST_NEGATIVE_FIXNUM 	== SCM_SRS((long)LONG_MIN, 2)
+ * - long ints 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.
+ * - numbers are encoded using two's complement.
+ *   The implementation of the bitwise scheme level operations is based on
+ *   this assumption.
+ * - ... add more
  */
 
 #ifdef HAVE_LIMITS_H
 # include <limits.h>
-# ifdef UCHAR_MAX
+#endif
-#  define SCM_CHAR_CODE_LIMIT (UCHAR_MAX+1L)
+
-# else
+#ifdef CHAR_BIT
-#  define SCM_CHAR_CODE_LIMIT 256L
+# define SCM_CHAR_BIT CHAR_BIT
-# endif /* def UCHAR_MAX */
+#else
-# define SCM_FIXNUM_BIT (LONG_BIT - 2)
+# define SCM_CHAR_BIT 8
-# define SCM_MOST_POSITIVE_FIXNUM (LONG_MAX>>2)
+#endif
-# ifdef _UNICOS			/* Stupid cray bug */
+
-#  define SCM_MOST_NEGATIVE_FIXNUM ((long)LONG_MIN/4)
+#ifdef LONG_BIT
-# else
+# define SCM_LONG_BIT LONG_BIT
-#  define SCM_MOST_NEGATIVE_FIXNUM SCM_SRS((long)LONG_MIN, 2)
+#else
-# endif				/* UNICOS */
+# define SCM_LONG_BIT (SCM_CHAR_BIT * sizeof (long) / sizeof (char))
+#endif
+
+#ifdef UCHAR_MAX
+# define SCM_CHAR_CODE_LIMIT (UCHAR_MAX + 1L)
 #else
 # define SCM_CHAR_CODE_LIMIT 256L
-# define SCM_FIXNUM_BIT 30
+#endif
-# define SCM_MOST_POSITIVE_FIXNUM ((long)((unsigned long)~0L>>3))
+
-# if (0 != ~0)
-#  define SCM_MOST_NEGATIVE_FIXNUM (-SCM_MOST_POSITIVE_FIXNUM-1)
-# else
-#  define SCM_MOST_NEGATIVE_FIXNUM (-SCM_MOST_POSITIVE_FIXNUM)
-# endif /*  (0 != ~0) */
-#endif /* def HAVE_LIMITS_H */
 
 
 #ifdef STDC_HEADERS

libguile/numbers.h

@@ -52,7 +52,6 @@
 
 
 
-
 /* Immediate Numbers 
  *
  * Inums are exact integer data that fits within an SCM word.
@@ -63,6 +62,11 @@
  * SCM_INUMP (SCM_CAR (x)) can give wrong answers.
  */
 
+#define SCM_FIXNUM_BIT (SCM_LONG_BIT - 2)
+#define SCM_MOST_POSITIVE_FIXNUM ((1L << (SCM_FIXNUM_BIT - 1)) - 1)
+#define SCM_MOST_NEGATIVE_FIXNUM (-SCM_MOST_POSITIVE_FIXNUM - 1)
+
+
 /* SCM_SRS is signed right shift */
 #if (-1 == (((-1) << 2) + 2) >> 2)
 # define SCM_SRS(x, y) ((x) >> (y))
@@ -111,15 +115,7 @@
 /* SCM_INTBUFLEN is the maximum number of characters neccessary for the
  * printed or scm_string representation of an exact immediate.
  */
-
+#define SCM_INTBUFLEN (5 + SCM_LONG_BIT)
-#ifndef SCM_CHAR_BIT
-# define SCM_CHAR_BIT 8
-#endif /* ndef SCM_CHAR_BIT */
-#ifndef SCM_LONG_BIT
-# define SCM_LONG_BIT (SCM_CHAR_BIT*sizeof(long)/sizeof(char))
-#endif /* ndef SCM_LONG_BIT */
-#define SCM_INTBUFLEN (5+SCM_LONG_BIT)
-