Properly scoped `for` in R.

for.r

`for` = function (var, seq, expr) {
    eval(substitute(.Primitive('for')(var, seq, expr),
                    list(var = substitute(var),
                         seq = substitute(seq),
                         expr = substitute(expr))))
}

for (i in 1 : 5) {
    j = i
    cat(i)
}
# 12345

i
# Error: object 'i' not found
j
# Error: object 'j' not found

Of course the above is merely a proof of concept and fails when there’s a conflict between variable names in the expressions and the argument names. For instance, this fails:

seq = 10
for (var in 1 : seq) print (var)