TODO

Ideas for future development
 * Config file for preferred settings
 * Saved state (start back up with last stack and modes)
 * Support for different 'displays'
   * Non-interactive (read input, print final value, no extras)
   * Simple with or without readline
   * TUI with status and extra info
     * Show modes rad/deg, polar/rect
	 * Show error messages
	 * Memory usage? CPU usage?
 * Constants library (interactive lookup for lesser-known constants)
   * phi c
 * More functions (long list)
   * hex bin oct
   * eng sci engsi
   * htonl ntohl be le
   * pow hypot fib root roots div(integer division)
   * max min mode
   * conj real imag
   * rsa_info
   * cidr netmask =net
   * db bd (ratio/decibel support)
   * modulo(modular math mode) down(toggle downcasting)
   * clreg store recall regs
   * ncdf(normal prob cdf) invn(inverse of ncdf)
 * N-d vector support [ x y z ]
   * parse / cross / dot / add / subtract / scaler
 * Interval support? x+-y / [x,y]
 * Modes
   * Modular arithmetic mode
   * Fixed bit math (for debugging C math issues, show over/under-flow bit)
 * Graphing? WTF? That's fancy.
 * More debug support
   * logging ?
   * debug for types
   * debug for units
 * Multi-processor support for things that can run in parallel
 * Timeouts for runaway calculations