dadt 0.0.2

DADT -- Algebraic Data Type for D

About

Algebraic Data Type For D. Parsing ADT declare expression and generate D code in compile time.

Example

Option

import dadt.parse;

enum option_code = `
type Option(T) =
  | Some of T
  | None`;

mixin(genCode(cast(TypeDeclare)DADT(option_code).buildAST));
/*
  genCode will generate automatically:
    - interface Option(T) {}
    - class Some(T) : Option!(T) {
        T _0;
        this (T _0) {
          this._0 = _0;
        }
      }
    - class None(T) : Option!(T) {}
    // helper functions
    - Some!(T) some(T)(T _0) {
        return new Some!T(_0);
      }
    - None!(T) none(T)() {
        return new None!(T);
      }
    // pattern matching function
    - _RETURN_TYPE_OF_MATCH_WITH_Option matchWithOption!(
      _RETURN_TYPE_OF_MATCH_WITH_Option,
      T,
      choices...)(Option!(T) arg) {}
*/

// If you define bind(>>= in Haskell) function...

auto bind(T, U)(Option!(T) arg, U function(T) proc) {
  import std.traits;

  static if (is(U == void)) {
    alias R = void;
  } else static if (__traits(isSame, TemplateOf!(U), Option)
      || __traits(isSame, TemplateOf!(U), Some) || __traits(isSame, TemplateOf!(U), None)) {
    alias R = U;
  } else {
    alias R = Option!U;
  }

  if ((cast(Some!T)arg) !is null) {
    T val = (cast(Some!T)arg)._0;

    static if (is(R == void)) {
      proc(val);
      return;
    }
    static if (is(R == U)) {
      static if (__traits(isSame, TemplateOf!(U), Option) || __traits(isSame,
          TemplateOf!(U), Some) || __traits(isSame, TemplateOf!(U), None)) {
        return proc(val);
      }
    } else {
      return some(proc(val));
    }
  } else {
    static if (is(R == void)) {
      return;
    }
    static if (is(R == U)) {
      return cast(Option!(TemplateArgsOf!U))none!(TemplateArgsOf!U);
    } else {
      static if (is(R == None!U)) {
        return none!U;
      } else {
        throw new Error("<1>Error in bind! <incompatible type was given>");
      }
    }
  }
}

void testForOption() {
  Option!int opt = some(100);

  opt.matchWithOption!(Option!int, int,
      (Some!int _) => (int x) => x % 2 == 0 ? some(x) : none!(int),
      (None!int _) => none!(int))
    .matchWithOption!(void, int,
      (Some!int _) => (int x) => writeln("x is Some of ", x),
      (None!int _) => writeln("x is None"));

  Option!int ret = matchWithOption!(Option!int, int,
      (Some!int _) => (int x) => some(x * x),
      (None!int _) => none!(int))(opt);

  ret.matchWithOption!(void, int,
      (Some!int _) => (int x) => writeln("x is ", x),
      (None!int _) => writeln("None!"));

  opt.matchWithOption!(Option!int, int,
      (Some!int _) => (int x) => x % 2 == 0 ? some(10) : none!int,
      (None!int _) => _)
     .matchWithOption!(void, int,
         (Some!int _) => writeln("Some"),
         (None!int _) => writeln("None"));

  opt.matchWithOption!(Option!string, int,
      (Some!int _) => (int x) => x % 2 == 0 ? some("x % 2 == 0 !!") : none!string,
      (None!int _) => none!string)
      .bind((string x) => writeln(x));
}

Binary Tree

enum binaryTree_code = `
type Tree(T) =
  | Node of Tree!(T) * Tree!(T)
  | Leaf of T
`;

mixin(genCode(cast(TypeDeclare)DADT(binaryTree_code).buildAST));

string indent(size_t n) {
  string ret;
  foreach (i; 0 .. n) {
    if (i % 2) {
      ret ~= "|   ";
    } else {
      ret ~= "||  ";
    }
  }
  return ret;
}

string toString(T)(Tree!T tree, size_t depth = 0) {
  import std.string;

  string indent_str = indent(depth);
  // dfmt off
  return tree.matchWithTree!(string, T,
      (Node!(int) _) => (Tree!int l, Tree!int r) => `
%s|---<left>%s
%s|
%s|---<right>%s`.format(indent_str, toString!(T)(l, depth + 1),
                        indent_str,
                        indent_str, toString!(T)(r, depth + 1)),
      (Leaf!(int) _) => (int v) => "%s".format(v));
  // dfmt on
}

void testForBinaryTree() {
  Tree!int ti = node(node(leaf(1), leaf(2)), node(leaf(3), leaf(4)));
  toString!int(ti).writeln;
}

Either

enum codeEither = `
type Either(T, U) =
  | Right of T
  | Left of U
`;

mixin(genCode(cast(TypeDeclare)DADT(codeEither).buildAST));

Option!(T) isEitherRight(T, U)(Either!(T, U) arg) {
  if ((cast(Right!(T, U))arg) !is null) {
    T val = (cast(Right!(T, U))arg)._0;
    return some(val);
  } else {
    return none!T;
  }
}

auto then(T, U)(Option!(T) arg, U function(T) proc) {
  static if (is(U == void)) {
    alias R = void;
  } else {
    alias R = Option!U;
  }

  if ((cast(Some!T)arg) !is null) {
    T val = (cast(Some!T)arg)._0;
    proc(val);
  }
}

void testForEither() {
  Either!(int, string) funcEither(int x) {
    if (x % 2 == 0) {
      return right!(int, string)(x * x);
    } else {
      return left!(int, string)("error");
    }
  }

  Either!(int, string) e1 = funcEither(2), e2 = funcEither(3);

  e1.isEitherRight!(int, string).then((int x) => writeln(x));
}

Deriving show

You can use deriving keyword.

enum option_code = `
type Option(T) =
  | Some of T
  | None
  [@@deriving show]
`;

mixin(genCode(cast(TypeDeclare)DADT(option_code).buildAST));
// genCode will generate...
    - interface Option(T) {}
    - class Some(T) : Option!(T) {
        T _0;
        this (T _0) {
          this._0 = _0;
        }
      }
    - class None(T) : Option!(T) {}
    // helper functions
    - Some!(T) some(T)(T _0) {
        return new Some!T(_0);
      }
    - None!(T) none(T)() {
        return new None!(T);
      }
    // pattern matching function
    - _RETURN_TYPE_OF_MATCH_WITH_Option matchWithOption!(
      _RETURN_TYPE_OF_MATCH_WITH_Option,
      T,
      choices...)(Option!(T) arg) {}
    // Stringify Function!!!
    - string show_Option(T)(Option!(T) arg, string function(Option!(T)) optionalPrinter = null);

void testForOption2() {
  Option!int opt = some(100);
  writeln(opt.show_Option);
}

Syntax

DADT using pegged, and the below PEG is written in extend PEG grammar of pegged.(copied from source/dadt/parse.d)

DADT:
  TypeDeclare < "type" BaseConstructor "=" ConstructorList Deriving?

  BaseConstructor < TypeNameWithArgs / TypeNameWithoutArgs

  TypeName <~ !Keyword [A-Z_] [a-zA-Z0-9_]*
  
  Field < FieldOfArray / FieldWithArgs / FieldName
  FieldArgs < "()" / :"(" Field ("," Field)* :")"
  FieldWithArgs < FieldName "!" FieldArgs
  FieldOfArray < (FieldWithArgs / FieldName) ArrayBracket+
  FieldName <~ !Keyword [a-zA-Z_] [a-zA-Z0-9_]*

  ArrayBracket < UnsizedBracket / SizedBracket

  UnsizedBracket < "[]"
  SizedBracket < "[" ArraySize "]"
  ArraySize <~ [a-zA-Z0-9_]*

  TypeNameWithoutArgs < TypeName
  TypeNameWithArgs < TypeName ParameterList
  ParameterList < "()" / :"(" TypeName ("," TypeName)* :")"

  ConstructorWithField < "|" TypeName "of" Field ("*" Field)*
  Constructor <  "|" TypeName
  ConstructorDeclare < ConstructorWithField / Constructor
  ConstructorList < ConstructorDeclare+

  Deriving < "[@@deriving" DerivingArgs "]"
  DerivingArgs < DerivingArg ("," DerivingArg)* 
  DerivingArg <~ !Keyword [a-zA-Z_] [a-zA-Z0-9_]*

  Keyword <~ "of"
  Integer <~ digit+

LICENSE

DADT is released under the MIT License. Please see LICENSE for details. Copyright (C) 2018 Akihiro Shoji