Difference between revisions of "Beyond D2"

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== Motivation ==
 
  
This can be used as a centralized place to discuss parts of D2's design that are controversial or suboptimal in retrospect.
 
Also discussed here are features that would be worthy of consideration in a hypothetical successor for D2, let's call it D3 (or E!). 
 
This page came up from email thread http://forum.dlang.org/post/ygmtislwwhfftiqrujan@forum.dlang.org.
 
 
Desirable properties:
 
* move features & special syntax from language to library whenever possible
 
* increase syntax & feature orthogonality (no special case for strings, prefer explicit to implicit)
 
* increase DRY-ness of code
 
* design grammar to be easy to parse and provide reference compiler as a library
 
* feature AST macros to simplify a number of constructs
 
* prefer automatic attribute inference over manual annotation
 
 
Clarity of target language is a more important role than to try to stay as close as possible to D2's syntax. Indeed, automatic translation tools can easily take care of this given that D is easy to parse (Dscanner can already do this, module caveats that'll eventually be fixed).
 
 
== Features to drop ==
 
 
* remove language builtins (sort / reverse / foreach_reverse / complex numbers), see http://dlang.org/deprecate.html
 
 
* get rid of opSlice/opSliceAssign etc:
 
** a..b is instead syntax sugar for a Slice object:
 
** rationale for opSlice, opSliceAssign, vs a..b being syntax sugar for a Slice struct? http://forum.dlang.org/post/mailman.551.1365290408.4724.digitalmars-d-learn@puremagic.com
 
 
* get rid of C-style expression lists in parenthesis; these would be reserved for tuples
 
 
* strings: stop conflating range of code points with range of code units:
 
** "foo" represents a range of code points
 
** "foo".rep represents a range of code units, eg: immutable(char)[]
 
** This would remove a *lot* of special case code in phobos and make it easier to write generic code, eg, would remove need for distinguishing ElementType vs ForeachType
 
** I've discussed this in email:"iteration over a string"
 
** Andrei mentioned it here as well: http://forum.dlang.org/post/l3h49k$b6$1@digitalmars.com :  "It is my opinion that a better solution exists (in the form of making representation accessible only through a property .rep)"
 
 
* stop conflating paths with strings; would make a lot of code safer and cross platform; would still allow implicit conversion via alias this.
 
** http://forum.dlang.org/post/op.wx7lqwvx54xghj@puck.auriga.bhead.co.uk + code
 
 
* get rid of @property
 
 
* get rid of /**/ since we have nesting /++/
 
 
* pragma(msg,) shouldn't insert "\n" (easy to add, impossible to remove)
 
 
* remove 'version(foo)' in favor of: static if(versions.foo), which would be more orthogonal. versions is an implicitly imported module that contains (for example):
 
  version.osx=true
 
  version.posix=true
 
  version.windows=false
 
  //plus other versions defined on command line
 
=> no new syntax
 
 
== Safety ==
 
* default is @safe/@pure ; attributes are automatically inferred and exported in di interface files
 
 
== Separate Compilation ==
 
 
* is virtual by default a good idea with separate compilation model?
 
 
== Features to add ==
 
 
* AST macros 
 
** proposal: https://dl.dropboxusercontent.com/u/18386187/ast_macros.html#scroll_to_here
 
** would enable many features; eg:
 
*** supersedes: "proposal: a new string litteral to embed variables in a string" http://forum.dlang.org/post/mailman.94.1383254681.9546.digitalmars-d@puremagic.com
 
*** supersedes: "feature request: __ARGS__ for logging (cf __FILE__, __LINE__, __FUNC___)" http://forum.dlang.org/post/godmqvdatmjvkyjybkoa@forum.dlang.org
 
 
* python style named parameter arguments
 
 
* Yield return
 
 
* R-value references
 
 
* Safe references
 
 
* language syntax for tuples; unify syntax for compile time tuples with runtime tuples
 
** could follow DIP32 but use (a,b) syntax instead; we would get rid of C-style expression lists to enable this
 
 
=== Arrays and Ranges ===
 
 
* multidimensional indexing and slicing:
 
** https://github.com/D-Programming-Language/dmd/pull/443
 
** http://homepages.uni-regensburg.de/~nen10015/documents/D-multidimarray.html
 
 
* builtin slices with begin..end:step or begin..end..step
 
 
== Compilation ==
 
 
* proposal: lazy compilation model for compiling binaries: http://forum.dlang.org/post/mailman.1357.1371876331.13711.digitalmars-d@puremagic.com
 
 
* allow JIT code, to allow runtime eval statements (for REPL etc).
 
 
* Compiler as a library (eg llvm/clang toolchain)
 
 
* Compiler written in D2, and then bootstrapped from their as done in rust and many other languages
 
 
== Tooling ==
 
* Incremental compilation support in rdmd: http://d.puremagic.com/issues/show_bug.cgi?id=9673
 
* improved dmd/rdmd command line: http://wiki.dlang.org/DIP41
 
 
== Syntax changes ==
 
* full UFCS support: foo.mixin, foo.assert, foo.stringof, foo.typeof
 
 
* More lightweight syntax:
 
** Go style a := b meaning auto a = b
 
 
** semi-column optional
 
 
** Go style lightweight if/while/etc expressions that don't require () around the if statement:
 
<syntaxhighlight lang="d">
 
while x>=0 {...}
 
</syntaxhighlight>
 
 
== Language interop ==
 
* Allow transparently including C headers in code as in Go; could use swig behind the scenes
 
 
== More controversial features to add ==
 
* store code as AST,
 
** The 1st idea is to get rid of styleguides completely and allow people to read/write code with their preferred style. Codes gets stored and exchanged as AST; clients read the AST and converts it on the fly as source code in the user's preferred formatting.
 
** speeds up compilation: only currently modified code needs to get translation from source to AST
 
** More future proof and eases refactoring
 
 
 
----
 
Page originally created by Timothee Cour on 11/09/2013; copyright: public domain.
 
TODO: add discussion/DIP/webpage links to each item
 

Latest revision as of 05:52, 10 November 2013