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Ingy döt Net 2013-04-10 23:57:08 -07:00
parent 47bf37c096
commit b83f433714
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37
Task/Scope-modifiers/R/scope-modifiers-3.r Normal file
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x <- "global x"
print(x) #"global x"
local({ ## local({...}) is a shortcut for evalq({...}, envir=new.env())
## and is also equivalent to (function() {...})()
x <- "outer local x"
print(x) #"outer local x"
x <<- "modified global x"
print(x) #"outer local x" still
y <<- "created global y"
print(y) #"created global y"
local({
## Note, <<- is _not_ a global assignment operator. If an
## enclosing scope defines the variable, that enclosing scope gets
## the assignment. This happens in the order of evalution; a local
## variable may be defined later on in the same scope.
x <- "inner local x"
print(x) #"inner local x"
x <<- "modified outer local x"
print(x) #"inner local x"
y <<- "modified global y"
print(y) #"modified global y"
y <- "local y"
print(y) #"local y"
##this is the only way to reliably do a global assignment:
assign("x", "twice modified global x", globalenv())
print(evalq(x, globalenv())) #"twice modified global x"
})
print(x) #"modified outer local x"
})
print(x) #"twice modified global x"
print(y) #"modified global y"