Integrate a set of ordinary, coupled first order differential equations from to . On return all the variables are set up, so that only a new value of has to be given to continue integration.

`ystart`: Input/Output. Contains the initial values for input and the calculated solution as output.`nvar`: Input. The number of equations.`x1`: Input/Output. The starting value. Becomes on return.`x2`: Input. The final value.`eps`: Input. The desired accuracy as discussed in chapter 16.2 of [1].`h1`: Input. The initial step size.`hmin`: Input. The smallest allowed step size.`derivs`: Input. A function describing the ode's.`derivs(x, y, dy)`should set`dy`according to`dy`.- Return value: Output. Returns if there was no error, and an error code otherwise. These codes are described in Section .

- Author: Serge Droz, droz@physics.uoguelph.ca
- Comments: You have to use Numerical Recipe
notation, i.e. the first element in an array
`x`is`x[1]`and*not*`x[0]`. See the program`Lorenz`for an example.