# How to determine whether the rule of an DynamicalSystem instance is inplace?
**URL:** https://discourse.julialang.org/t/how-to-determine-whether-the-rule-of-an-dynamicalsystem-instance-is-inplace/123041
**Category:** Modelling & Simulations
**Tags:** dynamical-systems
**Created:** [November 25, 2024, 8:47am UTC](https://discourse.julialang.org/t/how-to-determine-whether-the-rule-of-an-dynamicalsystem-instance-is-inplace/123041 "2024-11-25T08:47:14Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@andreasmorr](https://discourse.julialang.org/u/andreasmorr)
#### Post date: [November 25, 2024, 8:47am UTC](https://discourse.julialang.org/t/how-to-determine-whether-the-rule-of-an-dynamicalsystem-instance-is-inplace/123041/1 "2024-11-25T08:47:14Z")
I would like to define a function that takes a DynamicalSystem `ds` as an argument and computes the Jacobian of `dynamic_rule(ds)` for further analysis. For this, it would be good to know whether `dynamic_rule(ds)` returns an inplace function or out-of-place. Is there such a functionality? Would it be safe to use `m = first(methods(dynamic_rule(ds)))` and then ask `m.nargs==4` for and inplace function?
---
### Author:  [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)
#### Post date: [November 25, 2024, 8:50am UTC](https://discourse.julialang.org/t/how-to-determine-whether-the-rule-of-an-dynamicalsystem-instance-is-inplace/123041/2 "2024-11-25T08:50:25Z")
Check `Base.hasmethod`?
---
### Author:  [@Datseris](https://discourse.julialang.org/u/Datseris)
#### Post date: [November 25, 2024, 8:59am UTC](https://discourse.julialang.org/t/how-to-determine-whether-the-rule-of-an-dynamicalsystem-instance-is-inplace/123041/3 "2024-11-25T08:59:01Z")
There is a function for that, ‘isinplace’ that operates on the dynamical system directly.
CU!
George