2019-03-31 22:44:13 +01:00
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REM Types library for mal in BBC BASIC
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REM This library should be the only thing that understands the
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REM implementation of mal data types in BBC BASIC. All other
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REM code should use routines in this library to access them.
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REM As far as other code is concerned, a mal object is just an
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REM opaque 32-bit integer, which might be a pointer, or might not.
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REM Following the 8-bit BASIC implementation, we currently have two
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REM arrays, Z%() containing most objects and S$() containing strings
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REM (referenced from Z%()).
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REM See ../basic/mem.in.bas for data representations.
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DEF PROCtypes_init
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LOCAL i%
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DIM Z%(1000), S$(1000)
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FOR i% = 0 TO 15
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Z%(i%) = 0
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NEXT i%
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Z%(0) = 32: REM nil
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Z%(2) = 1+32: REM false
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Z%(4) = 1+32: Z%(5) = 1: REM true
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Z%(6) = 6+32: REM empty list
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next_Z% = 16
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next_S% = 0
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ENDPROC
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DEF FNtype_of(val%)
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=Z%(val%) AND 31
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2019-04-06 00:54:30 +01:00
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DEF FNmalloc(size%)
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LOCAL val%
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val% = next_Z%
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next_Z% += size%
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=val%
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2019-03-31 22:44:13 +01:00
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REM ** Nil **
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DEF FNnil
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=0
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REM ** Integers **
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DEF FNis_int(val%)
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=FNtype_of(val%) = 2
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DEF FNalloc_int(ival%)
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LOCAL val%
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2019-04-06 00:54:30 +01:00
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val% = FNmalloc(2)
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2019-03-31 22:44:13 +01:00
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Z%(val%) = 2+32
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Z%(val% + 1) = ival%
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=val%
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DEF FNunbox_int(val%)
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IF NOT FNis_int(val%) THEN ERROR 1, "Not an integer"
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=Z%(val% + 1)
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REM ** Symbols **
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DEF FNis_symbol(val%)
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=FNtype_of(val%) = 5
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DEF FNalloc_symbol(sval$)
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LOCAL s%
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s% = next_S%
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next_S% += 1
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S$(s%) = sval$
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2019-04-06 00:54:30 +01:00
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val% = FNmalloc(2)
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2019-03-31 22:44:13 +01:00
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Z%(val%) = 5+32
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Z%(val% + 1) = s%
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=val%
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DEF FNunbox_symbol(val%)
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IF NOT FNis_symbol(val%) THEN ERROR 1, "Not a symbol"
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=S$(Z%(val% + 1))
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REM ** Lists **
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DEF FNempty
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=6
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DEF FNalloc_pair(car%, cdr%)
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LOCAL val%
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2019-04-06 00:54:30 +01:00
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val% = FNmalloc(3)
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2019-03-31 22:44:13 +01:00
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Z%(val% + 0) = 6+32
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Z%(val% + 2) = car%
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Z%(val% + 1) = cdr%
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=val%
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DEF FNis_empty(val%)
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=val% = FNempty
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DEF FNis_list(val%)
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=FNtype_of(val%) = 6
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DEF FNlist_car(val%)
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IF NOT FNis_list(val%) THEN ERROR 1, "Can't get car of non-list"
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IF Z%(val% + 1) = 0 THEN ERROR 1, "Can't get car of empty list"
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=Z%(val% + 2)
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DEF FNlist_cdr(val%)
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IF NOT FNis_list(val%) THEN ERROR 1, "Can't get cdr of non-list"
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IF Z%(val% + 1) = 0 THEN ERROR 1, "Can't get cdr of empty list"
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=Z%(val% + 1)
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