Bidirectional Spreadsheet with Interval Constraint Solving
P6/10April 18, 2026
WhatA spreadsheet tool where users can set constraints on output cells and have it automatically compute valid input ranges using interval union arithmetic.
SignalThe author built the interval calculator specifically to power a 'backwards updating spreadsheet' — suggesting a real need for tools where you define desired outputs and the system tells you what inputs are feasible, which is fundamentally different from how every spreadsheet works today.
Why NowInterval union arithmetic research (2017 paper) has matured enough to be implemented practically in browser-native TypeScript, and the rise of no-code/low-code tools has primed users to expect smarter computational interfaces.
MarketFinancial modelers, engineers doing sensitivity analysis, and operations researchers who currently build Monte Carlo simulations or use Solver add-ins; ~$5B spreadsheet tools market; competes with Excel Solver and @RISK but from a fundamentally different angle.
MoatDeep technical implementation of interval union arithmetic is genuinely hard — most developers don't understand the math — creating a meaningful knowledge moat and switching cost once workflows are built on constraint-based spreadsheets.
Show HN: I made a calculator that works over disjoint sets of intervalsView discussion ↗ · Article ↗ · 302 pts · April 18, 2026
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