container: Extending Base 'R' Lists

# is.iterable
expect_true(is.iterable(Container$new()))
expect_false(is.iterable(1))

# Iterator constructor works as expected
expect_error(Iterator$new(), 'argument "x" is missing')
expect_error(Iterator$new(list()), "x must be iterable or subsettable")
e = new.env()
e$a = 1
expect_error(Iterator$new(e), "must be iterable or subsettable")

expect_equal(Iterator$new(NULL)$length(), 0)
expect_false(Iterator$new(NULL)$has_next())
expect_equal(Iterator$new(list(), .subset = .subset)$length(), 0)
expect_false(Iterator$new(list(), .subset = .subset)$has_next())
expect_equal(Iterator$new(1:3)$length(), 3)
expect_equal(Iterator$new(factor(1:2))$length(), 2)
expect_equal(Iterator$new(list("a", mean))$length(), 2)
expect_equal(Iterator$new(Container$new())$length(), 0)
expect_equal(Iterator$new(Container$new(1, 2, 3))$length(), 3)
expect_equal(Iterator$new(factor(letters[1:2]))$length(), 2)

# the position of the iterator can be accessed
x <- 1:5
it <- Iterator$new(x)
expect_equal(it$pos(), 0)
for (i in x) {
    expect_equal(it$get_next(), i)
    expect_equal(it$pos(), i)
}

# iterator can be moved to begin of the sequence
it <- Iterator$new(1:3)
expect_equal(it$pos(), 0)
it$begin()
expect_equal(it$pos(), 1)
expect_equal(it$get_value(), 1)

# it can be checked if Iterator has next element
expect_true(Iterator$new(1:5)$has_next())
expect_false(Iterator$new(1)$next_iter()$has_next())

# the value behind the iterator can be retrieved
it <- Iterator$new(1:5)
expect_error(it$get_value())
it$next_iter()
expect_equal(it$get_value(), 1)
it$next_iter()
expect_equal(it$get_value(), 2)

# the next value can be retrieved while incrementing the iterator
it <- Iterator$new(1)
expect_true(it$has_next())
expect_equal(it$get_next(), 1)
expect_false(it$has_next())

# Iterator can be reset
it <- Iterator$new(1:3)
expect_equal(it$pos(), 0)

while (it$has_next()) it$next_iter()
expect_equal(it$pos(), 3)
expect_equal(it$reset_iter()$pos(), 0)


# Iterator works as expected
s <- "Hello World!"
s.split <- strsplit(s, split="")[[1]]
it <- Iterator$new(s.split)
s2 <- ""
while(it$has_next()) s2 <- paste0(s2, it$get_next())
expect_equal(s2, s)
expect_false(it$has_next())
expect_error(it$get_next())

# Iterator works by reference on Container object
co = container(1, 2, 3)
it = co$iter()
it$next_iter()

expect_equal(it$get_value(), list(1))
co$discard(1)
expect_equal(it$get_value(), list(2))
co$discard(2)
expect_equal(it$get_value(), list(3))
co$clear()
expect_error(it$get_value(), "iterator does not point at a value")
co$add(4)
expect_equal(it$get_value(), list(4))
expect_equal(it$pos(), 1)

# Iterator works by reference on Dict object
d = dict(a = 1, b = 2)
it = d$iter()
it$next_iter()
expect_equal(it$get_value(), list(a = 1))
d$discard_at("a")
expect_equal(it$get_value(), list(b = 2))

# Iterator works by reference on Set object
s = setnew(a = 1, 2, 3)
it = s$iter()
it$next_iter()
expect_equal(it$get_value(), list(a = 1))
s$discard(1)
expect_equal(it$get_value(), list(2))


# .is.subsettable
.is.subsettable = container:::.is.subsettable
fac = as.factor(1:3)
expect_false(is.vector(fac))
expect_true(.is.subsettable(fac))
form = formula(y ~ x + 1)
expect_false(is.vector(form))
expect_true(.is.subsettable(form))
expect_true(.is.subsettable(1))
expect_true(.is.subsettable(data.frame(a = 1)))
expect_true(.is.subsettable(expression(x + 1)))

expect_false(.is.subsettable(list()))
expect_true(.is.subsettable(list(), .subset = .subset))