🚀 go-pugleaf

In a truly functional language (i.e. no side effects at all), a function
for altering a large data structure (adding an entry to a dictionary,
for example) would be written as:

	dictionary_add(dictionary, entry) returns dictionary;
	/* return a copy of dictionary with entry added to it */

This is very costly, however.  If side effects were allowed, you could
do it at a much smaller cost:

	dictionary_add(dictionary, entry);
	/* add entry to dictionary */

Is there some way to have a language with no side effects, yet still be
able to solve this class of problems in a practical way?  If not what is
the minimum amount of comprimise that must be made?


George