Re: [Rd] Trying to understand the search path and namespaces

From: Duncan Murdoch <murdoch.duncan_at_gmail.com>
Date: Mon, 15 Nov 2010 20:43:44 -0500

Hadley Wickham wrote:
> Hi all,
>
> I'm trying to understand how the search path and namespaces interact.
> For example, take the devtools package which suggests the testthat
> package. Here's what the search path looks like after I load each of
> those packages:

Luke Tierney wrote up a nice description of this a few years ago. It's either on developer.r-project.org, or in an old issue of R News.

Duncan Murdoch

>
>> library(devtools)
>> search()
> [1] ".GlobalEnv" "package:devtools" "package:stats"
> [4] "package:graphics" "package:grDevices" "package:utils"
> [7] "package:datasets" "package:methods" "Autoloads"
> [10] "package:base"
>> library(testthat)
>> search()
> [1] ".GlobalEnv" "package:testthat" "package:devtools"
> [4] "package:stats" "package:graphics" "package:grDevices"
> [7] "package:utils" "package:datasets" "package:methods"
> [10] "Autoloads" "package:base"
>
> My question is this: when I execute the test function in devtools
> function it calls the the test_package function in the testthat
> package - but that function is located higher up the search path - how
> does R find it?
>
> (I ask this question because I'm trying to simulate package loading
> from within R to simplify the development cycle, but something is
> missing in my knowledge of namespaces, and so I have the devel
> versions of my packages can't access packages that are loaded after
> they are)
>
> Hadley
>



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