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Added Cyc_is_list()

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Justin Ethier 2018-12-12 13:10:10 -05:00
parent ac78347d59
commit 7c8076e433
2 changed files with 34 additions and 0 deletions
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1
include/cyclone/runtime.h
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@ -421,6 +421,7 @@ double MRG32k3a (double seed);
int equal(object, object);
object equalp(object, object);
object Cyc_has_cycle(object lst);
object Cyc_is_list(object lst);
//object Cyc_is_boolean(object o);
#define Cyc_is_boolean(o) (make_boolean(o == boolean_f || o == boolean_t))
#define Cyc_is_pair(o) ((is_object_type(o) && ((list) o)->tag == pair_tag) ? boolean_t : boolean_f)

33
runtime.c
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@ -779,6 +779,39 @@ object Cyc_has_cycle(object lst)
}
}
/**
* Predicate - is the object a proper list?
* Based on `Cyc_has_cycle` so it is safe to call on circular lists.
*/
object Cyc_is_list(object lst)
{
object slow_lst, fast_lst;
if ((lst == NULL)){
return boolean_t;
} else if (is_value_type(lst)) {
return boolean_f;
} else if (is_object_type(lst) && type_of(lst) != pair_tag) {
return boolean_f;
}
slow_lst = lst;
fast_lst = cdr(lst);
while (1) {
if (fast_lst == NULL)
return boolean_t;
if (Cyc_is_pair(fast_lst) == boolean_f)
return boolean_f; // Improper list
if ((cdr(fast_lst)) == NULL)
return boolean_t;
if (Cyc_is_pair(cdr(fast_lst)) == boolean_f)
return boolean_f; // Improper
if (slow_lst == fast_lst)
return boolean_t; // Cycle; we have a list
slow_lst = cdr(slow_lst);
fast_lst = cddr(fast_lst);
}
}
/**
* Write string representation of a double to a buffer.
* Added code from Chibi Scheme to print a ".0" if the