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README.md

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+# mathtools
+mathtools is a program for computing various mathematical results that would be
+tedious to compute by hand.
+
+## Why?
+Obviously, libraries, software packages, and websites exist for these sort of
+calculations, but there are tradeoffs with any approach. Rather than needing to
+write a script, use a REPL, or load a webpage, this allows for an approach more
+like standard CLI utilities such as [GNU
+factor](https://www.gnu.org/software/coreutils/factor).
+
+Generally, I've opted to implement routines for problems that are best solved
+with *algorithms*, rather than *formulas*. For instance, the quadratic formula,
+while useful, is basically plug and chug, and thus isn't implemented here. On
+the other hand, determining whether a number is prime is a little more tedious
+to do by hand, so it's provided as a routine.
+
+## Available routines
+Available routines include:
+* convergents of a periodic continued fraction
+* solving systems of linear congruences with the Chinese remainder theorem
+* discrete logarithm
+* greatest common divisor
+* primality testing
+* Jacobi symbol
+* modular inverse
+* modular square root
+* multiplicative order
+* integer partitions
+* solving Pell equations
+* primitive root modulo n
+* area of a simple polygon from vertex coordinates
+* sieves for totient function, divisor function, Mobius function, and more
+* repetend of the continued fraction of a square root
+* Stirling numbers
+* summatory functions