return SCM_UNSPECIFIED; /* not reached */
}
+/* Intern a symbol whose name is the LEN characters at NAME in OBARRAY.
+
+ OBARRAY should be a vector of lists, indexed by the name's hash
+ value, modulo OBARRAY's length. Each list has the form
+ ((SYMBOL . VALUE) ...), where SYMBOL is a symbol, and VALUE is the
+ value associated with that symbol (in the current module? in the
+ system module?)
+
+ To "intern" a symbol means: if OBARRAY already contains a symbol by
+ that name, return its (SYMBOL . VALUE) pair; otherwise, create a
+ new symbol, add the pair (SYMBOL . SCM_UNDEFINED) to the
+ appropriate list of the OBARRAY, and return the pair.
+
+ If softness is non-zero, don't create a symbol if it isn't already
+ in OBARRAY; instead, just return #f.
+
+ If OBARRAY is SCM_BOOL_F, create a symbol listed in no obarray and
+ return (SYMBOL . SCM_UNDEFINED).
+
+ If OBARRAY is scm_symhash, and that doesn't contain the symbol,
+ check scm_weak_symhash instead. */
+
#ifdef __STDC__
SCM
scm_intern_obarray_soft (char *name, scm_sizet len, SCM obarray, int softness)
scm_hash = scm_strhash (tmp, i, SCM_LENGTH(obarray));
+ /* softness == -1 used to mean that it was known that the symbol
+ wasn't already in the obarray. I don't think there are any
+ callers that use that case any more, but just in case...
+ -- JimB, Oct 1996 */
if (softness == -1)
- goto mustintern_symbol;
+ abort ();
retry_new_obarray:
for (lsym = SCM_VELTS (obarray)[scm_hash]; SCM_NIMP (lsym); lsym = SCM_CDR (lsym))
return SCM_BOOL_F;
}
- mustintern_symbol:
lsym = scm_makfromstr (name, len, SCM_SYMBOL_SLOTS);
SCM_SETLENGTH (lsym, (long) len, scm_tc7_msymbol);
}
+/* Intern the symbol named NAME in scm_symhash, and give it the value VAL.
+ NAME is null-terminated. */
#ifdef __STDC__
SCM
scm_sysintern (char *name, SCM val)
extern int scm_symhash_dim;
+/* SCM_LENGTH(SYM) is the length of SYM's name in characters, and
+ SCM_CHARS(SYM) is the address of the first character of SYM's name.
+
+ Beyond that, there are two kinds of symbols: ssymbols and msymbols,
+ distinguished by the 'S' bit in the type.
+
+ Ssymbols are just uniquified strings. They have a length, chars,
+ and that's it. They use the scm_tc7_ssymbol tag (S bit clear).
+
+ Msymbols are symbols with extra slots. These slots hold a property
+ list and a function value (for Emacs Lisp compatibility), a hash
+ code, and a flag to indicate whether their name contains multibyte
+ characters. They use the scm_tc7_msymbol tag.
+
+ We'd like SCM_CHARS to work on msymbols just as it does on
+ ssymbols, so we'll have it point to the symbol's name as usual, and
+ store a pointer to the slots just before the name in memory. Thus,
+ you have to do some casting and pointer arithmetic to find the
+ slots; see the SCM_SLOTS macro.
+
+ In practice, the slots always live just before the pointer to them.
+ So why not ditch the pointer, and use negative indices to refer to
+ the slots? That's a good question; ask the author. I think it was
+ the cognac. */
+
#define SCM_SYMBOLP(x) (SCM_TYP7S(x)==scm_tc7_ssymbol)
#define SCM_LENGTH(x) (((unsigned long)SCM_CAR(x))>>8)
#define SCM_LENGTH_MAX (0xffffffL)
#ifndef TAGSH
#define TAGSH
/* Copyright (C) 1995,1996 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
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
- *
+ *
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
- *
+ *
* You should have received a copy of the GNU General Public License
* along with this software; see the file COPYING. If not, write to
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*
* If you write modifications of your own for GUILE, it is your choice
* whether to permit this exception to apply to your modifications.
- * If you do not wish that, delete this exception notice.
+ * If you do not wish that, delete this exception notice.
*/
\f
-/** This file defines the format of SCM values and cons pairs.
+/** This file defines the format of SCM values and cons pairs.
** It is here that tag bits are assigned for various purposes.
**/
#define SCM_NIMP(x) (!SCM_IMP(x))
/* Here is a summary of tagging in SCM values as they might occur in
- * SCM variables or in the heap.
+ * SCM variables or in the heap.
*
* low bits meaning
*
- *
+ *
* 0 Most objects except...
* 1 ...glocs and structs (this tag valid only in a SCM_CAR or
* in the header of a struct's data).
* 100 --- IMMEDIATES
*
* Looking at the seven final bits of an immediate:
- *
+ *
* 0000-100 short instruction
* 0001-100 short instruction
* 0010-100 short instruction
* 1110-100 immediate characters
* 1111-100 ilocs
*
- * Some of the 0110100 immediates are long instructions (they dispatch
+ * Some of the 0110100 immediates are long instructions (they dispatch
* in two steps compared to one step for a short instruction).
* The two steps are, (1) dispatch on 7 bits to the long instruction
* handler, (2) dispatch on 7 additional bits.
*
* 101 & 111 --- tc7_ types
*
- * tc7_tags are 7 bit tags ending in 1x1. These tags occur
- * only in the CAR of heap cells.
+ * tc7_tags are 7 bit tags ending in 1x1. These tags
+ * occur only in the CAR of heap cells, and have the
+ * handy property that all bits of the CAR above the
+ * bottom eight can be used to store a length, thus
+ * saving a word in the body itself. Thus, we use them
+ * for strings, symbols, and vectors (among other
+ * things).
*
* SCM_LENGTH returns the bits in "length" (see the diagram).
* SCM_CHARS returns the data cast to "char *"
* that applies to a particular type, see the header file
* for that type.
*
+ * Sometimes we choose the bottom seven bits carefully,
+ * so that the 4- and 1-valued bits (called the D and S
+ * bits) can be masked off to reveal a common type.
+ *
* TYP7S(X) returns TYP7, but masking out the option bit S.
* TYP7D(X) returns TYP7, but masking out the option bit D.
* TYP7SD(X) masks out both option bits.
*
+ * For example, all strings have 001 in the 'xxx' bits in
+ * the diagram above, the D bit says whether it's a
+ * substring, and the S bit says whether it's a multibyte
+ * character string.
+ *
* for example:
* D S
- * scm_tc7_string = Gxxx0101
- * scm_tc7_mb_string = Gxxx0111
- * scm_tc7_substring = Gxxx1101
- * scm_tc7_mb_substring = Gxxx1111
+ * scm_tc7_string = G0010101
+ * scm_tc7_mb_string = G0010111
+ * scm_tc7_substring = G0011101
+ * scm_tc7_mb_substring = G0011111
+ *
+ * TYP7DS turns all string tags into tc7_string; thus,
+ * testing TYP7DS against tc7_string is a quick way to
+ * test for any kind of string.
*
- * TYP7S turns tc7_mb_string into tc7_string and
+ * TYP7S turns tc7_mb_string into tc7_string and
* tc7_mb_substring into tc7_substring.
*
- * TYP7D turns tc7_mb_substring into tc7_mb_string and
+ * TYP7D turns tc7_mb_substring into tc7_mb_string and
* tc7_substring into tc7_string.
*
- * TYP7DS turns all string tags into tc7_string.
- *
* Some TC7 types are subdivided into 256 subtypes giving
* rise to the macros:
*
* TYP16S functions similarly wrt to TYP16 as TYP7S to TYP7,
* but a different option bit is used (bit 2 for TYP7S,
* bit 8 for TYP16S).
- *
- */
+ * */
* figure out Xs type. X may be a cons pair, in which case the
* value SCM_CAR (x) will be either an immediate or non-immediate value.
* X may be something other than a cons pair, in which case the value SCM_CAR (x)
- * will be a non-object value.
+ * will be a non-object value.
*
* All immediates and non-immediates have a 0 in bit 0. We additionally preserve
* the invariant that all non-object values stored in the SCM_CAR of a non-immediate
#define SCM_CELLP(x) (!SCM_NCELLP(x))
#define SCM_NCELLP(x) ((sizeof(scm_cell)-1) & (int)(x))
-/* See numbers.h for macros relating to immediate integers.
+/* See numbers.h for macros relating to immediate integers.
*/
#define SCM_ITAG3(x) (7 & (int)x)
#define scm_tc_dblc (scm_tc16_flo|SCM_REAL_PART|SCM_IMAG_PART)
-/* Smob types 2 and 3:
+/* Smob types 2 and 3:
*/
#define scm_tc16_bigpos 0x027f
#define scm_tc16_bigneg 0x037f
\f
-/* {Immediate Values}
+/* {Immediate Values}
*/
enum scm_tags
#define SCM_MAKISYM(n) (((n)<<9)+0x74L)
#define SCM_MAKIFLAG(n) (((n)<<9)+0x174L)
-/* This table must agree with the declarations
+/* This table must agree with the declarations
* in repl.c: {Names of immediate symbols}.
*
* These are used only in eval but their values
*/
-/* For cons pairs with immediate values in the CAR
+/* For cons pairs with immediate values in the CAR
*/
#define scm_tcs_cons_imcar 2:case 4:case 6:case 10:\
HCoop / bpt / guile.git / commitdiff