I've been studying interval arithmetic for the past few weeks and it's a really interesting field because while there is a ton of super interesting research published over the past decades, it has never really gotten the recognition that it deserves, IMO. One reason for this is that standard interval arithmetic has really poor handling of division by intervals containing zero. If you compute 1 / [-1, 2] in regular interval arithmetic, you get either [-∞, +∞], or you have to say that the operation is undefined. Both solutions are virtually useless. The real answer of course is [-∞, -1] U [0.5, +∞]: i.e. a union of two disjoint intervals. This is useful because you can confidently exclude a non empty set of the real numbers ([-1, 0.5]) from the set of possible values that you can get by dividing 1 by a number between -1 and 2. But this definition of interval division yields a value that is not an interval. This is a problem if you want to define a closed arithmetic system, where you can build and evaluate arbitrary expression over interval values. (This behavior extends to any non continuous function like tan() for example, which is implemented in my project - not without difficulties!) Well the obvious solution is to define your arithmetic over disjoint unions of intervals. This is the subject of a 2017 paper called "Interval Unions" by by Schichl, H., Domes, F., Montanher, T. and Kofler, K.. This open-source project I made implements interval union arithmetic in TypeScript in the form of a simple interactive calculator, so you can try it out for yourself! The underlying TypeScript library is dependency free and implements interval union arithmetic over IEEE 754 double precision floats (JS native number type) with outward rounding. This guarantees accuracy of interval results in the presence of rounding issue inherent to floating point. Comments URL: https://news.ycombinator.com/item?id=47812341 Points: 180 # Comments: 32
Built this as a simple tool for estimating roof area, materials, and replacement cost without having to request a quote first. A lot of homeowners have no good way to sanity-check roofing costs early on, and contractors often still do the first pass manually. Roofing Calculator is meant to be a lightweight starting point: enter a few inputs, get a rough estimate, and understand project scope before talking to anyone. Interested in feedback from people in construction, home services, or anyone who has dealt with roof replacement before. Comments URL: https://news.ycombinator.com/item?id=47790556 Points: 1 # Comments: 0
Article URL: https://calcpocket.com Comments URL: https://news.ycombinator.com/item?id=47784249 Points: 1 # Comments: 2
I built a set of lightweight financial decision tools (buy vs rent, house hacking, retirement, debt payoff) after trying to model a condo purchase for my girlfriend. Backstory: My girlfriend was looking into buying a condo, and I was trying to convey to her how the costs add up, even compared to renting. I knew from my personal experience with house-hacking in Seattle right out of college that the simple "renting is throwing money down the drain" philosophy can lead you to rush into buying properties without actually understanding the financial implications. I was having a tough time conveying this to her verbally, so I built a "house-hacking calculator" for her using Codex to visually model how investing a down payment and renting compares to buying a condo. Once I finished that initial prototype for her, I realized I had built something more generally useful. A lot of the available financial tools online are either overly complex for decisions like this (require modeling tax brackets, classifying bonds/investment allocations, etc.), overly simplistic (just input your mortgage rate and balance, don't consider that you can reinvest proceeds after sale), and/or require you to input a bunch of contact information before you get the answers you're looking for. There was room for a free, responsive, lightweight tool that would immediately show to you how changing variables like down payment, interest rate, and inflation rate can impact your financial standing, without requiring you to sell your contact information. Once I built the house-hacking calculator with these design philosophies in mind, I had a lot of fun expanding to other tools like retirement planning, budget allocation, debt paydown, rent vs buy, etc. It was also really rewarding when I learned how I could host my own static webpages on Cloudflare for just $10/year for the domain. Hopefully folks find the tools useful, and I'd love feedback on any faulty assumptions, missing inputs, and other tools I should add. Comments URL: https://news.ycombinator.com/item?id=47772986 Points: 1 # Comments: 0
Article URL: https://bytecalculators.com/rag-cost-calculator Comments URL: https://news.ycombinator.com/item?id=47755853 Points: 2 # Comments: 0