build_limits_function: Convert limits argument to a function
Description
Parses the `limits` argument for [ff()] and [sff()] terms. Accepts
`NULL` (no limits), a function, or string shortcuts "s<t" / "s<=t".
Usage
build_limits_function(limits)
Value
A function(s, t) returning logical, or `NULL`.
Arguments
- limits
Either `NULL`, a function(s, t) returning logical, or
a string "s<t" or "s<=t".