Identifiers can be very long

Comparing them directly is inefficient

Lexical analyzer can immediately replace them with references to symbol objects

• hash table stores mapping of strings to symbols
• pointers equal iff strings equal
• useful to also have unique integer ID for each symbol (for storing within trees)

No need to undo the mapping of strings to symbol objects

• except for space reasons in very long compilation tasks

Use the Trie dictionary data structure.