Damien Katz: What Sucks About Erlang

Damien Katz says Erlang works very well for CouchDB and other network servers, but he finds it awkward for tests and front-end application work. He points to context-sensitive syntax, restrictive if expressions, string handling as integer lists, verbose records, brittle memory failure behavior, and limited code organization.

Reading notes

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• Erlang’s syntax uses expression separators that vary by context, which makes editing and refactoring harder than in languages with more uniform terminators.
• if expressions must match at least one branch or they throw if_clause, and they cannot call user-defined functions in conditional expressions.
• case is presented as a better substitute for many if uses, but it shares the same requirement to match at least one branch.
• Erlang has no string type; strings are lists of integers, which makes string handling less direct and makes strings hard to distinguish from integer lists.
• Katz says Erlang fits recursive, functional code and shared-nothing concurrency well, especially for servers and database internals.
• For test code and other changing application code, immutable variables and repeated rebinding can require more edits than equivalent code in C or JavaScript.
• Records are described as verbose and limited, because record type syntax must be repeated where members are accessed and the feature compiles down to tuples.
• He says records are hard to use from the REPL and in debugging, where they appear as tuples instead of records.
• When the VM cannot get memory from the OS, Katz reports that Erlang can terminate the whole VM rather than only the failing process.
• He says automatic restart is not built in and may need a separate watchdog process, while the built-in heart process also dies with the VM.
• Erlang’s main organizational unit is the source file module, so creating something like a class means creating another file and adding it to build and source control.
• Katz finds several bundled libraries and tools uneven in quality, including Inets httpd, Xmerl, GUI tools on Windows and OS X, and the OTP build and versioning system.
• He ends by saying Erlang has major strengths and real-world value, but that its weaknesses are not discussed enough.