Works like `list(...)`, but returns an immutable sequence backed by measured finger-tree internals.
Examples
x <- flexseq(1, 2, 3)
x
#> FingerTree <size=3, named=no>
#> monoids: none
#>
#> [[1]]
#> [1] 1
#>
#> [[2]]
#> [1] 2
#>
#> [[3]]
#> [1] 3
#>
x2 <- flexseq("a", "b", "c")
x2
#> FingerTree <size=3, named=no>
#> monoids: none
#>
#> [[1]]
#> [1] "a"
#>
#> [[2]]
#> [1] "b"
#>
#> [[3]]
#> [1] "c"
#>