README.md

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   2
   3 Hope
   4 ====
   5
   6 A quest for a "standard" library with uniform, composable abstractions.
   7
   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).
  13
  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).
  17
  18
  19 Conventions
  20 -----------
  21
  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.
  24
  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
  35   thinking...)
  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
  40
  41 Abstractions
  42 ------------
  43
  44 ### Monads
  45
  46 A class of burritos, used for sequencing operations on a particular data type.
  47 Defined in `hope_gen_monad`, implemented as:
  48
  49 - `hope_result`: for composition of common functions returning
  50   `{ok, Val} | {error, Reason}`. An alternative to exceptions, which makes the
  51   error conditions apparent in the spec/signature. Analogous to Haskell's
  52   `Data.Either a b`, Jane Street Core's (OCaml) `('a, 'b) Result.t`, Rust's
  53   `Result<T, E>`
  54 - `hope_option`: for expressing and composing the intention that the value may
  55   or may not be available. An alternative to the common `undefined` (which is
  56   equivalent to the dreaded `null`). Analogous to ML's (SML, OCaml, etc)
  57   `'a Option.t`, Rust's `Option<T>` and Haskell's `Data.Maybe a` [1].
  58
  59
  60 ### Containers
  61
  62 A class of abstract data types to which we have exclusive access and can put
  63 things in and take them out. See issue #9
  64
  65 - Operations on all abstract types of containers _should_ share a common lexicon
  66 - Concrete implementations of an abstract data type _must_ be swapable
  67
  68 #### Dictionary
  69
  70 Defined in `hope_gen_dictionary`, implemented as:
  71
  72 - `hope_kv_list`. Equivalent to orddict/proplist. Operations implemented with
  73   BIFs from `lists` module, where possible
  74
  75 TBD:
  76 - `hope_hash_tbl`. API around stdlib's `dict`
  77 - `hope_gb_dict`. API around stdlib's `gb_trees`
  78
  79 #### Set
  80
  81 TBD:
  82 - `hope_hash_set`. API around stdlib's `sets`
  83 - `hope_gb_set`. API around stdlib's `gb_sets`
  84
  85 #### Queue
  86
  87 TBD
  88
  89 Should include both FIFO (queue) and LIFO (stack), so that user can swap if a
  90 different order is desired.
  91
  92 Should we attempt to include priority queues or make them a separate abstract
  93 type?
  94
  95 #### Sequence
  96
  97 TBD
  98
  99 Not yet defined and only partially implemented as:
 100
 101 - `hope_list`
 102
 103
 104 ### Resources
 105
 106 A class of abstract systems to which we share access with an unknown number of
 107 users and can make requests to perform operations which may not get done for
 108 any number of reasons.
 109
 110 #### Storage
 111
 112 TBD
 113
 114 See issue #11
 115
 116
 117 [1]: http://en.wikipedia.org/wiki/Option_type