_head(l: list): any

Returns the first element of l. If l is empty, returns ERR.

_head(<46, 83, 25, "hike!">) == 46

_head(b: binding): binding

Returns a binding with only one <name, value> pair equal to the first element of b. If b is empty, returns ERR.

_head([ foo = 1, bar = 2, moxy = TRUE ]) == [ foo = 1 ]
_head([]) == ERR

_tail(l: list): list

Returns the list consisting of all elements of l, in order, except the first. If l is empty, returns ERR.

_tail(<"the", "lowest", "highest", "point">) == <"lowest", "highest", "point">

_tail(b: binding): binding

Returns the binding consisting of all <name, value> pairs of b, in order, except the first. If b is empty, returns ERR.

_tail([ foo = 1, bar = 2, moxy = TRUE ]) == [ bar = 2, moxy = TRUE ]