Ecco una funzione ricorsiva bizzarra che ho scritto per aiutare a capire le relazioni tra sys.parent() e l'ambiente:funzioni nidificate, sys.parent e gli ambienti in R
dive = function(level = 1, max.depth = 5)
{
m = match.call()
print(paste("sys.frame() says", format(sys.frame())))
print(paste("sys.parent() says", sys.parent()))
print(paste("sys.frame(sys.parent()) says", format(sys.frame(sys.parent()))))
m[[2]] = m[[2]]+1
if(m[[2]] > max.depth)
stop("Not actually an error -- we're just tripping out!")
eval(m)
}
esecuzione della funzione dà
dive(level = 1, max.depth = 5)
[1] "sys.frame() says <environment: R_GlobalEnv>"
[1] "sys.parent() says 0"
[1] "sys.frame(sys.parent()) says <environment: R_GlobalEnv>"
[1] "sys.frame() says <environment: R_GlobalEnv>"
[1] "sys.parent() says 1"
[1] "sys.frame(sys.parent()) says <environment: 0x2831dd0>"
[1] "sys.frame() says <environment: R_GlobalEnv>"
[1] "sys.parent() says 4"
[1] "sys.frame(sys.parent()) says <environment: 0x3b1dff8>"
[1] "sys.frame() says <environment: R_GlobalEnv>"
[1] "sys.parent() says 7"
[1] "sys.frame(sys.parent()) says <environment: 0x3b31c68>"
[1] "sys.frame() says <environment: R_GlobalEnv>"
[1] "sys.parent() says 10"
[1] "sys.frame(sys.parent()) says <environment: 0x3c238c0>"
Error in dive(level = 5, max.depth = 5) :
Not actually an error -- we're just tripping out!
C'è un sacco di cose qui, ma terrò la mia domanda semplice: perché sys.parent() incrementa la prima volta da 1 (0-1) poi successivamente da 3 (ossia, 1 , 4, 7, 10 ...)?
Si potrebbe trovare utile questo: https://github.com/hadley/devtools/wiki/Environments#function-environments – hadley
anche qui: http://obeautifulcode.com/R/How- R-Ricerche-E-Reperti-Stuff / – zkurtz