simon/post-scarcity
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Just poking around and trying to remember where the problems are.

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Simon Brooke 2023-04-08 10:36:59 +01:00
parent fae4a4d444
commit cbcced70b2
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GPG key ID: A7A4F18D1D4DF987
8 changed files with 240 additions and 218 deletions
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11
src/arith/integer.c
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@ -100,13 +100,12 @@ __int128_t cell_value( struct cons_pointer c, char op, bool is_first_cell ) {
__int128_t int128_to_integer( __int128_t val,
struct cons_pointer less_significant,
struct cons_pointer new ) {
struct cons_pointer cursor = NIL;
__int128_t carry = 0;
if ( MAX_INTEGER >= val ) {
carry = 0;
} else {
carry = val >> 60;
carry = val >> INTEGER_BIT_SHIFT;
debug_printf( DEBUG_ARITH,
L"int128_to_integer: 64 bit overflow; setting carry to %ld\n",
( int64_t ) carry );
@ -136,7 +135,7 @@ struct cons_pointer make_integer_128( __int128_t val,
less_significant =
make_integer( ( long int ) val & MAX_INTEGER,
less_significant );
val = val >> 60;
val = val >> INTEGER_BIT_SHIFT;
}
} while ( nilp( result ) );
@ -290,7 +289,7 @@ struct cons_pointer multiply_integers( struct cons_pointer a,
/* if xj exceeds one digit, break it into the digit dj and
* the carry */
carry = xj >> 60;
carry = xj >> INTEGER_BIT_SHIFT;
struct cons_pointer dj = make_integer( xj & MAX_INTEGER, NIL );
/* destructively modify ri by appending dj */
@ -320,7 +319,7 @@ struct cons_pointer multiply_integers( struct cons_pointer a,
}
/**
* don't use; private to integer_to_string, and somewaht dodgy.
* don't use; private to integer_to_string, and somewhat dodgy.
*/
struct cons_pointer integer_to_string_add_digit( int digit, int digits,
struct cons_pointer tail ) {
@ -361,7 +360,7 @@ struct cons_pointer integer_to_string( struct cons_pointer int_pointer,
while ( accumulator > 0 || !nilp( next ) ) {
if ( accumulator < MAX_INTEGER && !nilp( next ) ) {
accumulator +=
( pointer2cell( next ).payload.integer.value << 60 );
( pointer2cell( next ).payload.integer.value << INTEGER_BIT_SHIFT );
next = pointer2cell( next ).payload.integer.more;
}
int offset = ( int ) ( accumulator % base );

10
src/arith/peano.h
View file

@ -13,10 +13,18 @@
#define PEANO_H
/**
* The maximum value we will allow in an integer cell.
* The maximum value we will allow in an integer cell: one less than 2^60:
* (let ((s (make-string-output-stream)))
* (format s "0x0~XL" (- (expt 2 60) 1))
* (string-downcase (get-output-stream-string s)))
* "0x0fffffffffffffffl"
*
* So left shifting and right shifting by 60 bits is correct.
*/
#define MAX_INTEGER ((__int128_t)0x0fffffffffffffffL)
#define INTEGER_BIT_SHIFT (60)
bool zerop( struct cons_pointer arg );
struct cons_pointer negative( struct cons_pointer arg );