# exprel class

(Shortest import: `from brian2.core.functions import exprel)`

class brian2.core.functions.exprel(arg)

  Bases: `Function`

  Represents `(exp(x) - 1)/x`.

  The benefit of using `exprel(x)` over `(exp(x) - 1)/x` is that the latter is prone to cancellation under finite precision arithmetic when x is close to zero, and cannot be evaluated when x is equal to zero.

  Methods

  `eval`(arg) | Returns a canonical form of cls applied to arguments args.
  `fdiff`([argindex]) | Returns the first derivative of this function.

  Details

  classmethod eval(arg)

    Returns a canonical form of cls applied to arguments args.

  fdiff(argindex=1)

    Returns the first derivative of this function.

## Tutorials and examples using this

- Example COBAHH

- Example IF_curve_Hodgkin_Huxley

- Example advanced/exprel_function

- Example advanced/float_32_64_benchmark

- Example compartmental/hh_with_spikes

- Example compartmental/hodgkin_huxley_1952

- Example compartmental/lfp

- Example frompapers/Stimberg_et_al_2019/example_3_bisection

- Example frompapers/Stimberg_et_al_2019/example_3_bisection_standalone

- Example frompapers/Wang_Buszaki_1996