[erlang-questions] [ANN] power_shell 1.1.2 has been released

Richard O'Keefe raoknz@REDACTED
Fri Sep 20 05:45:22 CEST 2019


"1. Clearly indicate evaluation rather than actual execution."
What does that mean?  Execution is evaluation is execution.


On Fri, 20 Sep 2019 at 15:20, Maxim Fedorov <maximfca@REDACTED> wrote:

> There are two reasons to name is eval/3:
> 1. Clearly indicate evaluation rather than actual execution.
> 2. Avoid clash with erlang:apply/3. When power_shell is started as an
> application (e.g. application:start(power_shell) in Erlang shell), it
> becomes a part of the shell, so you can just type eval(mod, fun,
> [args]).
>
> As for the project name, it is purely historical, and has no relation
> to Microsoft.
>
> Maxim
>
> On Wed, 18 Sep 2019 at 21:06, Richard O'Keefe <raoknz@REDACTED> wrote:
> >
> > The example is power_shell:eval(dist_util, gen_challenge, []).
> > With the arguments being Module, Function, Arguments, why is
> > it not called power_shell:apply/3?
> >
> > Since I'm currently trying to learn PowerShell, I was initially
> > confused by the module name.
> >
> > On Thu, 19 Sep 2019 at 16:02, Maxim Fedorov <maximfca@REDACTED> wrote:
> >>
> >> power_shell is an application providing a convenient way to evaluate
> >> functions extracted from compiled *.beam file, or read from *.erl
> >> source.
> >>
> >> How do we use it at WhatsApp?
> >>
> >> Debugging on production machines: evaluating functions that are not
> >> exported. For example, dist_util.erl contains gen_challenge/0, but it
> >> is not accessible without making a change to OTP kernel application.
> >> Using power_shell:eval(dist_util, gen_challenge, []) yields the
> >> desired result.
> >>
> >> Common Tests: testing functions that are not exported. We want to test
> >> against production build, providing production API.
> >>
> >> Development: changing *.erl file and immediately evaluating functions
> >> directly from *.erl file (no need to c(mymodule) to compile and load
> >> updated code).
> >>
> >> Package is available on hex:
> >> https://hex.pm/packages/power_shell
> >>
> >> Source code is available on GitHub:
> >> https://github.com/WhatsApp/power_shell
> >>
> >> Enjoy!
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