Why “lookup” is being discussed
The most recent Hacker News stories and comments contributing to this topic's mentions.
indeed, i've had an 'old ipad' mounted to the underside of my kitchen cabinets for over a decade (I think we're on our third one) and the old ipad is pretty damn good as an airp…
by tpurves · Oct 13, 2026
You can’t put everything in a lookup table with the lookup cost being O(1). If the things you have to memoize are super-linear, suppose you need to store some value related to a…
by fooker · Oct 13, 2026
That particular lookup table would be O(n), and it wouldn't support unbounded inputs.
by hansvm · Oct 13, 2026
Yes, but writing down the address in the lookup table takes log(2^n)=n bits, so the claim of an O(1) lower bound is simply wrong.
by _alternator_ · Oct 13, 2026
The above 2^n is just the extreme. There’s always baby steps to that direction. If you want you can point an agent at any known nlogn algorithm (eg. Sorting) and quickly get sim…
by AnotherGoodName · Oct 13, 2026
>> only slightly less corrupt than this The values do not bare comparison. Lookup the whitewater controversy (Clintons, 1990s). The loans in that fiasco were in the low hundreds…
by sandworm101 · Oct 13, 2026
Interest
Proportion of Hacker News items mentioning "lookup" over time.
Mentions
Total number of Hacker News items mentioning "lookup" over time.
In computer science, a lookup table (LUT) is an array that replaces runtime computation of a mathematical function with a simpler array indexing operation, in a process termed as direct addressing. The savings in processing time can be significant, because retrieving a value from memory is often faster than carrying out an "expensive" computation or input/output operation. The tables may be precalculated and stored in static program storage, calculated as part of a program's initialization phase (memoization), or even stored in hardware in application-specific platforms. Lookup tables are also used extensively to validate input values by matching against a list of valid items in an array and, in some programming languages, may include pointer functions to process the matching input. FPGAs also make extensive use of reconfigurable, hardware-implemented, lookup tables to provide programmable hardware functionality. LUTs differ from hash tables in that, to retrieve a value with key , a hash table would store the value in the slot where is a hash function i.e. is used to compute the slot, while in the case of LUT, the value is stored in slot , thus directly addressable. Read more on Wikipedia