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| A basic RPN calculator from command line |
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Everything is passed from the command line. There isn't any interactive mode.
This calculator use Reverse Polish Notation (see http://en.wikipedia.org/wiki/Reverse_Polish_Notation for details).

Example:
        Consider the following infix expression :
                 5 + (3 * 4) / 6 - 2
        This could be evaluated with rpnc using those arguments :
                rpnc 5 3 4 * 6 / 2 - +
        In order to avoid the shell expander another option is :
                rpnc 5 3 4 . 6 / 2 - +

Results are printed to standard output. Intermediate results could be shown with
the "=" operator. The program return the number of elements (operators and values)
left into the stack. If the whole expression has been evaluated it returns zero.

The operators list follows :
    +         Addition
    -         Substraction
    *         Multiplication
    .         Multiplication
    /         Division
    ^         Raise to a power
    **        Raise to a power
    pow       Raise to a power
    atan2     Inverse tangent of a quotient
    hypot     Hypotenuse by the Pythagorean formula
    mod       Modulo operation
    inv       Multiplicative inverse
    sqrt      Square root
    cbrt      Cube root
    sin       Sinus of a radian angle
    cos       Cosine of a radian angle
    tan       Tangent of a radian angle
    asin      Inverse sine in radians
    acos      Inverse cosine in radians
    atan      Inverse tangent in radians
    sinh      Hyperbolic sine
    cosh      Hyperbolic cosine
    tanh      Hyperbolic tangent
    asinh     Inverse hyperbolic sine
    acosh     Inverse hyperbolic cosine
    atanh     Inverse hyperbolic tangent
    exp       Natural exponential
    exp2      Base two exponential
    expm1     Natural exponential minus one
    log       Natural logarithm
    log10     Base-10 logarithm
    log2      Base two logarithm
    logb      Obtains the exponent
    log1p     Add the natural logarithm of one
    abs       Absolute value
    erf       Error function
    erfc      Complementary error function
    lgamma    Natural logarithm of the absolute value of the gamma function
    tgamma    True gamma function
    =         Show intermediate results
    pi        Pi constant
    c         Speed of light (m/s)
    e         Electron charge (C)
    me        Electron mass (kg)
    mp        Proton mass (kg)
    G         Gravitational constant (N.m^2/kg^2)
    g         Standard gravity (m/s^2)
    h         Planck constant (J.s)
    hbar      Dirac constant (J.s)
    eps0      Vacuum permittivity (F/m)
    mu0       Vacuum permeability (H/m)
    NA        Avogadro constant (mol^-1)
    stdT      Standard temperature (K)
    stdP      Standard pression (Pa)
    INF       Infinity
    +INF      Infinity
    -INF      Minus infinity
    version   Display version
    help      Display usage
    operators Display operators