spigot is a command-line streaming exact real calculator.
A normal calculating program, given a mathematical expression to evaluate, will want to know in advance how many digits of output are needed (if it even has that option), and if the expression includes more than one successive operation, then rounding errors will build up so that the last few digits are potentially wrong, or perhaps more in some cases (e.g. if significance loss occurs).
spigot, by contrast, does not output any digit of the answer until it’s sure that the digit is right, and it will keep generating digits until you tell it to stop.
Also, spigot is ‘streaming’ in the sense that if you tell it to do computations on a number you’ve previously stored in a file (perhaps to very high precision) or a number it’s reading from a pipe, then it will begin producing output as soon as it’s read enough of the input to know how the output starts.
The downside is that spigot is very slow compared to the usual kind of computer arithmetic. But it can be useful if you really need a lot of digits for some reason (e.g. a large number of digits of mathematical constants are sometimes incorporated into cryptographic algorithms), or as a cross-check on other calculating systems.
Website: www.chiark.greenend.org.uk/~sgtatham/spigot
Support:
Developer: Simon Tatham
License: MIT License
spigot is written in C++. Learn C++ with our recommended free books and free tutorials.
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