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6 A quest for a "standard" library with uniform, composable abstractions.
8 Originally motivated by a desire for an error monad and generic option type
9 operations, and stood for _Higher Order Programming in Erlang_. Soon after, I
10 wished all standard containers used consistent conventions and protocols (such
11 as consistent accessor names, argument positioning rules and expression of
12 semantics with option and result types).
14 Here lies an experiment to see what something like that could look like. As all
15 proper experiments should, this one is used daily in production projects (hence
16 the high-ish version number, 'cause semver).
22 I entertain any forward-thinking library design ideas, but more than anything
23 else, these are influenced by Jane Street's Core of the OCaml world.
25 - A module per data type implementation
26 - Name of the module is the name of the type
27 - Inside the module, the type it implements is always named t(..), such as:
28 `hope_foo:t()`, _not_ `hope_foo:foo()`
29 - t(..) is always the first argument
30 - Names of private records _may_ be short, such as: `#foo{}` or `#t{}` (Though
31 I'm second-guessing this idea, since seeing `{t, ..}` in stack traces is less
32 than helpful. I'm considering requiring fully-qualified names for all record
33 definitions and maybe short-handing what would've been `#t{..}` as
34 `-define(T, ?MODULE). -record(?T, {..}).`, which may be a bit ugly. Still
36 - Names of public records _must_ be fully qualified, such as: `#hope_module_record{}`
37 - Names of all modules _must_ be fully qualified, such as: `hope_module` (this
38 should go without saying, but just to be sure...)
39 - Keep the number of (anonymous) arguments "reasonably" low:
41 + 4 is suspicious but may be reasonable
42 + 5 is _very_ suspicious and probably unnecessary
43 + more than 5 is unacceptable, so consider reducing by:
44 1. revising abstractions, or, if not practical
45 2. creating a public record specifically for the purpose of passing
46 many arguents, which simulates labeled arguments. For an example see
47 https://github.com/ibnfirnas/oauth1_core where I used that technique
48 extensively (especially in oauth1_server.erl)
56 A class of burritos, used for sequencing operations on a particular data type.
57 Defined in `hope_gen_monad`, implemented as:
59 - `hope_result`: for composition of common functions returning
60 `{ok, Val} | {error, Reason}`. An alternative to exceptions, which makes the
61 error conditions apparent in the spec/signature. Analogous to Haskell's
62 `Data.Either a b`, Jane Street Core's (OCaml) `('a, 'b) Result.t`, Rust's
64 - `hope_option`: for expressing and composing the intention that the value may
65 or may not be available. An alternative to the common `undefined` (which is
66 equivalent to the dreaded `null`). Analogous to ML's (SML, OCaml, etc)
67 `'a Option.t`, Rust's `Option<T>` and Haskell's `Data.Maybe a` [1].
72 A class of abstract data types to which we have exclusive access and can put
73 things in and take them out. See issue #9
75 - Operations on all abstract types of containers _should_ share a common lexicon
76 - Concrete implementations of an abstract data type _must_ be swapable
80 Defined in `hope_gen_dictionary`, implemented as:
82 - `hope_kv_list`. Equivalent to orddict/proplist. Operations implemented with
83 BIFs from `lists` module, where possible
86 - `hope_hash_tbl`. API around stdlib's `dict`
87 - `hope_gb_dict`. API around stdlib's `gb_trees`
92 - `hope_hash_set`. API around stdlib's `sets`
93 - `hope_gb_set`. API around stdlib's `gb_sets`
99 Should include both FIFO (queue) and LIFO (stack), so that user can swap if a
100 different order is desired.
102 Should we attempt to include priority queues or make them a separate abstract
109 Not yet defined and only partially implemented as:
116 A class of abstract systems to which we share access with an unknown number of
117 users and can make requests to perform operations which may not get done for
118 any number of reasons.
127 [1]: http://en.wikipedia.org/wiki/Option_type