dictionary in other languages: it's a data structure that associates a key with a value. if, for example, we wanted to have an association between a and 1 and b and 2, we could use a map.
=| chart=(map @t @t) adds a noun to the subject with the default value of the (map @t @t) type, and gives that noun the face chart.
?. =((lent a) (lent b)) checks if the two tapes are the same length. if not, the program crashes.
|- creates a trap, a gate that is called immediately.
?: |(?=(~ a) ?=(~ b)) checks if either tape is empty. if this is true, we the program is finished and 