static bool __meminit defer_init(int nid, unsigned long pfn, unsigned long end_pfn) { static unsigned long prev_end_pfn, nr_initialised; if (early_page_ext_enabled()) return false; /* * prev_end_pfn static that contains the end of previous zone * No need to protect because called very early in boot before smp_init. */ if (prev_end_pfn != end_pfn) { prev_end_pfn = end_pfn; nr_initialised = 0; } /* Always populate low zones for address-constrained allocations */ if (end_pfn < pgdat_end_pfn(NODE_DATA(nid))) return false; if (NODE_DATA(nid)->first_deferred_pfn != ULONG_MAX) return true; /* * We start only with one section of pages, more pages are added as * needed until the rest of deferred pages are initialized. */ nr_initialised++; if ((nr_initialised > PAGES_PER_SECTION) && (pfn & (PAGES_PER_SECTION - 1)) == 0) { NODE_DATA(nid)->first_deferred_pfn = pfn; return true; } return false; }

function hasKey<O>(obj: O, key: PropertyKey): key is keyof O { return key in obj }

If there is no relationship between the value's type and the type in the type predicate, the guard would make no sense. For example, TypeScript won't allow a user-defined guard like this: function isString(value: Date): value is string { return typeof value === "string"; }

Two of the predominant types of relationships in knowledge-representation systems are predication and the universally quantified conditional.

It is based on the idea that each validation is encapsulated by a simple, stateless predicate that receives some input and returns either true or false.

the function you pass to the find method is called a predicate. The predicate here defines a boolean outcome based on conditions defined in the function itself, so that the find method can determine which value to find.