Frequently asked questions
These are the questions that come up most often about the Rust WASM Calculator, answered from the source code rather than from marketing copy. If a question you have is not here, the source is public and the operation pages document each function in detail.
Where the answers come from
Every answer below is checkable against the repository. The arithmetic, the error variants, and the limits all live in a single Rust source file, and the page behaviour lives in a single JavaScript file. The crate's 86 unit tests are the reference for the numeric claims on this site.
Where to look for more detail
Each answer here is a summary. The pages below carry the full behaviour, including the edge cases and the exact error text you will see when an input is out of range.
- Operations — every function, what it accepts, and which four errors it can raise.
- Errors — all four error messages verbatim, and what triggers each.
- Factorial — why the limit is 20 and the exact values from 0 to 20.
- Memory — MS, MR, MC and M+, and why C leaves the register alone.
- History — why square root and factorial appear in one history and not the other.
- Why Rust and WebAssembly — the reasoning behind the whole design.
- Limitations — what the calculator does not do, stated plainly.
- The f64 boundary — how values move between JavaScript and Rust.
- Testing — the two test suites and what each one covers.
Questions and answers
What is the Rust WASM Calculator?
It is a free browser calculator whose arithmetic engine is written in Rust and compiled to WebAssembly. It computes addition, subtraction, multiplication, division, square root, squaring, and factorial, and it keeps a memory register and a list of recent calculations.
Does it cost anything or need an account?
No. It is free, needs no account, and the source code is public on GitHub under the pigfox/rust-wasm-calc repository.
Does it work offline?
Once the page and the WebAssembly module have loaded, every calculation runs locally with no network access. The initial page load still requires a connection, and there is no offline installer or service worker.
Is my data private?
Yes. Calculations never leave the browser tab. The calculator has no backend, writes nothing to local storage or cookies, and makes no request when you press a button.
What is the largest number it can handle?
Ordinary arithmetic uses 64-bit floating point, which reaches roughly 10 to the power of 308. Factorial is the exception: it uses 64-bit unsigned integers and is capped at 20 factorial, or 2432902008176640000.
Why does 0.1 plus 0.2 not give exactly 0.3?
Because the calculator uses IEEE 754 64-bit floating point, in which 0.1 and 0.2 have no exact binary representation. The result is 0.30000000000000004. This is a property of the number format, not a bug, and it matches what every other floating point calculator does.
Who built the Rust WASM Calculator?
It was built by Peter Sjolin and is published by Pigfox LLC. The full source is available on GitHub.
Can I use the calculator engine in my own project?
Yes. The engine is a Rust crate that builds as both a native library and a WebAssembly module, so it can be used from Rust directly or imported into a web page as an ES module.