package pratter

Changelog

This project adheres to Semantic Versioning. Lines marked with 🧨 describe breaking changes.

[Unreleased]

[5.0.1] -- 2025-02-27

Internal edits to reduce the minimal supported ocaml version to 4.10.0.

[5.0] -- 2025-02-12

Changed

🧨 The Signature of expression has changed from

appl:('b -> 'b -> 'b) -> token:('a -> 'b)
-> ops:(('a, 'b) Operators.t)
-> ('a, 'b) parser

to

appl:('b -> 'b -> 'b) -> token:('a -> 'b)
-> ops:('a -> (fixity * float * 'b) list)
-> ('a, 'b) parser

Removed

The Operators module has been deleted.

[4.0] -- 2024-10-08

Changed

The parser is made functional: the use of camlp-streams has been dropped in favour of sequences of the Seq module. The parser is written in a monad.

🧨 The error `Op_conflict now takes a single argument instead of two.

🧨 Introduced a type for parsers. The function expression builds a parser that can then be run on any sequence with the run function.

🧨 A token can have different fixities depending on the context its in. For instance, the - can be declared both prefix and infix, resulting in - x - y being parsed as (-x) - y. Consequently the API changed. The parser now truly parses the input, meaning that the output datatype may be different from the input datatype: the main expression function changed from

• expression : ... -> 'a Stream.t -> 'a to
• expression : ... -> 'a Stream.t -> 'b.

Consequently, the ~appl argument of the expression function now operates on the output type, and a new argument ~token must be given which parses tokens that aren't operators.

The expression function also takes an Operators.t value instead of a function is_op: 'a -> (fixity * float) option to parse operators. To use the new datatype, the rule is the following. For any operator op

• if is_op op returns Some (Infix a, p), the operators parser must be built with infix f a p where f is a function that parses o and produces an output datatype.
• if is_op op returns Some (Prefix, p), then the operators parser must be built with prefix f p, where f verifies the aforementioned properties.
• if is_op op returns Some (Postfix, p), then the operators parser must be built with postfix f p, and f verifies the aforementioned properties.

🧨 Use camel case for errors: OpConflict changed to Op_conflict and TooFewArguments to Too_few_arguments.

Removed

🧨 Errors UnexpectedPostfix and UnexpectedInfix have been removed. If a infix operator appears postfix, it's handled by the token parser rather than the operator parser.

[3.0.1] -- 2023-11-06

Added

Lower bounds on test dependencies alcotest, qcheck and qcheck-alcotest.

[3.0] -- 2023-11-04

Changed

🧨 Removed the functor interface, the parser is a single function taking two functions and a stream of terms as parameters.

No more table type needed, the parser only needs a function is_op to distinguish operators from other tokens.

To port code, any snippet like

module S : SUPPORT = struct
  type term = ...
  type table = ...
  let get tbl t = ...
  let make_appl t u = ...
end
module P = Pratter.Make(S)

should be replaced by

let is_op t = ...
let appl t u = ...

where the following properties hold

• appl = S.make_appl
• ∃ tbl : S.table, get tbl = is_op

Under these assumptions, denoting tbl the value that makes the second hypothesis hold, we have P.expression tbl = Pratter.expression ~is_op ~appl

[2.0] -- 2022-06-15

Added

• Postfix operators
• Comparison against a YACC parser for a small arithmetic-like language of the form t ::= t t | t + t | - t | t * t | t = t | t !

Changed

• 🧨 Una constructor changed to Prefix
• 🧨 Bin constructor changed to Infix

• 🧨 Errors are encoded with a polymorphic variant rather than exceptions. To port code, replace sections of the form

    try let t = SupPrat.expression tbl s in e with
  | ... -> ...

  with

    match SupPrat.expression tbl s with
  | Ok t -> e
  | Error ... -> ...

[1.2.1] -- 2022-05-06

Added

• Property based testing with QCheck.

Changed

• Depends on camlp-streams (because Stdlib.Stream becomes deprecated in OCaml 4.14).
• New continuous integration recipe.

[1.2] -- 2021-05-05

Added

• Walkthrough in README.md.

Fixed

• Parsing a binary operator without left context fails.
• Binding power can be negative.

[1.1] -- 2021-01-23

Added

• Non associative operators
• Error handling on partially applied operators (which raises a Stream.Failure)

Changed

• One function get for operators in API
• make_appl does not use the table of operators

[1.0.1] -- 2021-01-16

Fixed

• Correct OCaml dependency
• Tests comply with OCaml 4.02

Added

• Gitlab continuous integration

[1.0] -- 2021-01-14

Changed

• API: parser uses a data structure passed as argument
• renamed CHANGELOG to CHANGELOG.md

[0.1.1] -- 2021-01-06

Added

• Initial version