[Rd] Trying to understand the search path and namespaces

From: Hadley Wickham <hadley_at_rice.edu>
Date: Mon, 15 Nov 2010 17:26:47 -0600


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:

> 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

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/

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