# gsldif input parameters - avram - a virtual machine code interpreter
avram - a virtual machine code interpreter

#### D.5.1 `gsldif` input parameters

The argument to the functions with mnemonics of `backward`, `central` or `forward` is a pair `(`f`,`x`)`, where f is the virtual machine code for a real valued function of a real variable, and x is the input to f where the derivative is sought. Real numbers are represented according to math.

The argument to the functions with mnemonics of `t_backward`, `t_central` or `t_forward` is a pair `((`f`,`t`),`x`)`, where f and x are as above, and t is a tolerance represented as a floating point number. The tolerance is passed through to the GNU Scientific library (GSL) differentiation routines.

When no tolerance is specified, the default is `1.0e-8`.