The Curry Howard isomorphism says that given a programming language with a expressive type system, a correspondence can be defined between propositions with types on the one hand, and proofs and programs on the other. In other words, we can express any mathematical claim as a type whose truth is proven by its instantiation. 

This means that a compiler can be used as a proof-checker. If the proof represented by the instantiation was invalid, then compilation should fail. 

Organization
 * There is some old experimental stuff I did in Scala a long time ago before I was fully prepared to build this thing for real. 
 * include/logic/intuitionistic.hpp : intuitionistic logic is a version of logic where propositions are about the existence of a proof rather than about truth. 
 * include/math/number/natural/peano.hpp : the peano axioms of the natural numbers. 
 
Further plans: 
 * finiteness
    * prime numbers
 * algebraic structures such as groups, rings, and fields. 
    * cyclic, symmetric, and alternating groups
    * integers and rationals
 * cauchy sequences
    * real numbers and calculus. 
 * linear algebra
    * complex numbers
    * affine spaces
    * exterior algebra
      * differentials
      * spinors
  * combine linear algebra and groups to get representation theory
  * combine linear algebra with algebra to get Galois theory
  * combine linear algebra with calculus to get differential geometry
  * finally can get to real math when comlplex analysis, differential geometry, and number theory all work together.