Lightwave3D
Expression PluginLightwave3D
Expression PluginEquation.p is an arithmetic expression evaluator which converts a string containing a valid mathematical equation into its floating point value. It is based on Eval113, a command-line-based expression evaluator which is Copyright (C) 1993 Will Menninger and has been put into public distribution under the GNU public license agreement. This derivative software is also covered by this license, I have made minor modifications to the source, and added several small glue modules to make this code into a Lightwave3D plug-in. The source is available.
Equation.p is a global-class plug-in module. This means that its functions are only available to other plug-ins, not to end users. To call Equation.p from a plug-in file, you must first get access to its functions by calling the global function with the name for the plug-in service, in this case "ExpressEval". If the plug-in is loaded in LW, the global function will return the address of an Evaluator structure, which has pointers to all the available functions. The definitions for this and other necessary structures are in the file lweval.h, which must be #included in your source.
The Evaluator structure has the following elements:
typedef struct {
char *symbol;
double value;
} ev_arg;
The following built-in functions are supported by the evaluator:
abs(x) absolute value acos(x) arccosine, return value in radians acosh(x) inverse hyperbolic cosine asin(x) arcsine, return value in radians asinh(x) inverse hyperbolic sine atan(x) arctangent, return value in radians atan2(y,x) arctangent of y/x, return value in radians atanh(x) inverse hyperbolic tangent bessi(m,x) bessel function Im(x) bessj(m,x) bessel function Jm(x) bessk(m,x) bessel function Km(x) ceil(x) round up cos(x) cosine, x in radians cosh(x) hyperbolic cosine dbessi(m,x) derivative of bessel function: Im'(x) dbessj(m,x) derivative of bessel function: Jm'(x) dbessk(m,x) derivative of bessel function: Km'(x) djroot(m,n) nth non-zero root of Jm'(x) exp(x) e (2.718..) raised to the power of x fact(n) factorial (n!) floor(x) round down jroot(m,n) nth non-zero root of Jm(x) ln(x) natural logarithm (base e) log(x) logarithm to the base 10 sgn(x) -1 if x<0, 0 if x=0, +1 if x>0 sin(x) sine, x in radians sinh(x) hyperbolic sine sqrt(x) squareroot tan(x) tangent, x in radians tanh(x) hyperbolic tangent rand(x) random value between 0.0 and 1.0, int part of x is seed noise(x,y,z) fractal noise ifeq(a,b,t,f) if a=b then t else f iflt(a,b,t,f) if a<b then t else f ifgt(a,b,t,f) if a>b then t else f iflte(a,b,t,f) if a<=b then t else f ifgte(a,b,t,f) if a>=b then t else f
Here are the constants available (and their values):
_acres_per_sq_km 247.1 _air_density 1.293 _air_mol_mass .02897 _atm_per_psi .06804 _avagadro 6.0220e23 _boltzmann 1.3807e-23 _c 2.997925e8 _cm_per_in 2.54 _coulomb_const 8.98755e9 _deg_per_rad 57.2958 _earth_esc_spd 1.12e4 _earth_grav 9.80665 _earth_mass 5.98e24 _earth_radius 6.37e6 _earth_to_moon 3.844e8 _earth_to_sun 1.496e11 _eps0 8.85419e-12 _erg_per_joule 1e7 _eulers_const .57721566490153286061 _ft_per_m 3.280839895 _g 6.672e-11 _gas_const 8.314 _gauss_per_tesla 1e4 _gm_per_oz 28.34952313 _golden_ratio 1.6180339887498948482 _h 6.6262e-34 _hbar 1.05459e-34 _joule_per_btu 1054.35 _joule_per_cal 4.184 _joule_per_ftlb 1.356 _joule_per_kwh 3.6e6 _kg_per_slug 14.59 _km_per_mi 1.609344 _knots_per_mph .86897624 _lbs_per_kg 2.204622622 _lit_per_gal 3.785411784 _me 9.1095e-31 _mn 1.67495e-27 _moon_grav 1.62 _moon_mass 7.35e22 _moon_period 2360448. _moon_radius 1.738e6 _mp 1.67265e-27 _mu0 1.256637e-6 _oz_per_gal 128. _pasc_per_atm 101325. _pasc_per_psi 6895. _pasc_per_torr 133.32 _pi 3.14159265358979323846 _qe 1.60219e-19 _solar_const 1350. _speed_sound 331. _sun_mass 1.99e30 _sun_radius 6.96e8 _watts_per_hp 745.712 _zero_deg_cels 273.15