• Sugerimos uma revisão introdutória, no módulo básico, na seção Ambientes e Caminho de busca
• Nessa introdução falaremos sobre: hierarquia, caminho de busca (caminho de pesquisa);
• Alguns objetos importantes em ambientes

# Ambiente
amb1 <- new.env()
# Verificando os seus parentais
rlang::env_parents(amb1, last = emptyenv())

##  [[1]] $ <env: global>
##  [[2]] $ <env: package:stats>
##  [[3]] $ <env: package:graphics>
##  [[4]] $ <env: package:grDevices>
##  [[5]] $ <env: package:utils>
##  [[6]] $ <env: package:datasets>
##  [[7]] $ <env: package:methods>
##  [[8]] $ <env: Autoloads>
##  [[9]] $ <env: package:base>
## [[10]] $ <env: empty>

# Promessa makeCluster
autoload("makeCluster", "parallel")
# Caminho de busca sem o pacote 'parallel'
search()
## [1] ".GlobalEnv"        "package:stats"     "package:graphics" 
## [4] "package:grDevices" "package:utils"     "package:datasets" 
## [7] "package:methods"   "Autoloads"         "package:base"

# Verificamos que 'makeCluster' esta como promessa
ls("Autoloads")
## [1] "makeCluster"
# Chamando a funcao
makeCluster
## function (spec, type = getClusterOption("type"), ...) 
## {
##     switch(type, PSOCK = makePSOCKcluster(names = spec, ...), 
##         FORK = makeForkCluster(nnodes = spec, ...), SOCK = snow::makeSOCKcluster(names = spec, 
##             ...), MPI = snow::makeMPIcluster(count = spec, ...), 
##         NWS = snow::makeNWScluster(names = spec, ...), stop("unknown cluster type"))
## }
## <bytecode: 0x000000000769b808>
## <environment: namespace:parallel>
# Verificando novamente o Caminho de busca,
# agora com o pacote 'parallel'
search()
##  [1] ".GlobalEnv"        "package:parallel"  "package:stats"    
##  [4] "package:graphics"  "package:grDevices" "package:utils"    
##  [7] "package:datasets"  "package:methods"   "Autoloads"        
## [10] "package:base"

x <- c(1, 2, 4)
mean(x)

## [1] 2.333333

• Pode se conter
• Semântica de referência
• Sem ocorrência de cópias

# Ambiente
amb1 <- new.env(hash = FALSE)
# Inserindo objetos nesse ambiente
amb1$a <- c(1, 2, 4); amb1$b <- "a"; amb1$d <- TRUE
# Inspecao do objeto.
Internal(inspect(amb1))
## @0x000000000db22758 04 ENVSXP g0c0 [REF(1)] <0x000000000db22758>
## FRAME:
##  @0x000000000db213a8 02 LISTSXP g0c0 [REF(1)] 
##    TAG: @0x00000000078ebb28 01 SYMSXP g0c0 [MARK,REF(128)] "d"
##    @0x000000000db1fa38 10 LGLSXP g0c1 [REF(3)] (len=1, tl=0) 1
##    TAG: @0x000000000db1c4b8 01 SYMSXP g0c0 [REF(10)] "b"
##    @0x000000000db1fae0 16 STRSXP g0c1 [REF(3)] (len=1, tl=0)
##      @0x0000000006369e78 09 CHARSXP g0c1 [MARK,REF(14),gp=0x61] [ASCII] [cached] "a"
##    TAG: @0x0000000006483320 01 SYMSXP g0c0 [MARK,REF(60)] "a"
##    @0x000000000db186f8 14 REALSXP g0c3 [REF(1)] (len=3, tl=0) 1,2,4
ENCLOS:
##  @0x0000000005fda628 04 ENVSXP g0c0 [MARK,REF(65535),GL,gp=0x8000] <R_GlobalEnv>

amb1$a[2] <- 10
.Internal(inspect(amb1))
## @0x000000000db22758 04 ENVSXP g0c0 [REF(1)] <0x000000000db22758>
## FRAME:
##  @0x000000000db213a8 02 LISTSXP g0c0 [REF(1)] 
##    TAG: @0x00000000078ebb28 01 SYMSXP g0c0 [MARK,REF(128)] "d"
##    @0x000000000db1fa38 10 LGLSXP g0c1 [REF(3)] (len=1, tl=0) 1
##    TAG: @0x000000000db1c4b8 01 SYMSXP g0c0 [REF(10)] "b"
##    @0x000000000db1fae0 16 STRSXP g0c1 [REF(3)] (len=1, tl=0)
##      @0x0000000006369e78 09 CHARSXP g0c1 [MARK,REF(16),gp=0x61] [ASCII] [cached] "a"
##    TAG: @0x0000000006483320 01 SYMSXP g0c0 [MARK,REF(62)] "a"
##    @0x000000000db186f8 14 REALSXP g0c3 [REF(1)] (len=3, tl=0) 1,10,4
## ENCLOS:
##  @0x0000000005fda628 04 ENVSXP g0c0 [MARK,REF(65535),GL,gp=0x8000] <R_GlobalEnv>
parent.env(amb1)
## <environment: R_GlobalEnv>