We now turn to the packages in the context
50.
Their important features are the
<#1159#>rule bases<#1159#> for evaluation of forward and inverse z-transforms, and
forward and inverse discrete-time Fourier transforms.
Application of these rule bases is triggered by calls to the
evaluation functions
51, 52, 53 and
54.
Such calls are automatically performed when 55 is
applied:~ thus, <#224#>TheFunction[ Z[n, z] [ Exp[- n] Step[n] ] ]<#224#> evaluates to
<#225#>ZTransform[ Exp[- n] Step[n], n, z ]<#225#>, which is then further evaluated
to an explicit form.