bolts ~refract-remove-returntype

Bolts Meta Programming Utility Library

Full API docs available here

Bolts is a utility library for the D programming language which contains a number of static reflection utilties that query compile time entities (traits) or transform them (meta). General utilties are in the modules traits and meta, and more specific ones are in dedicated modules (i.e. bolts.members provides utilities over a type's members).

Modules:

• meta: has functions that result in compile time entity transofrmations, including:
  • Flatten, AliasPack, Pluck, Zip, FilterMembersOf, RemoveAttributes.
• traits: has general utitlites that can query compile time entities. including:
  • isFunctionOver, isUnaryOver, isBinaryOver, isProperty, hasProperty, propertySemantics, areCombinable, isManifestAssignable, isOf, isSame, isNullType, StringOf, isRefType, isValueType, isLiteralOf, isLiteral, isCopyConstructable, isNonTriviallyCopyConstructable, protectionLevel, isTriviallyCopyConstructable, hasFunctionMember, areEquatable, isNullSettable, isNullTestable, isRefDecl, TypesOf
• members: has functions that allow you to query about the members of types
  • staticMembersOf, memberFunctionsOf, member (not eponymous)
• range: query ranges
  • isSortedRange, sortingPredicate, CommonTypeOfRanges
• aa: has functions that act on associative arrays
  • isKey (not eponymous)
• iz: super non-eponymous template that provides a lot of the functionality that's in the traits module with a different sytax that allows their usage in meta functions as well.
• experimental: contains experimental features signatures: working implementation of type signatures refraction: generate mixin strings to replicate a function, with some changes

Most functions here operate on any compile time entity. For example isUnaryOver works in both these situatons:

int i;
void f(int) {}
isFunctionOver!(f, int);
isFunctionOver!(f, 3);
isFunctionOver!(f, i);

Iz super template

The iz super template. Has a lot of the traits on types encapulated in one place. So if there's a trait that tells you something about a compile time entity, chances are iz will have it. E.g:

void f(int, float, string) {}
iz!f.functionOver!(int, float, string);
iz!f.functionOver!(3, float, "");

Member super template

The member super template, found in the bolts.members module is similar to the iz template but works on members of types only:

import bolts.members: member;
struct S {
    static void f() {}
}
assert(member!(S, "f").exists);
assert(member!(S, "f").protection == ProtectionLevel.public_);
assert(!member!(S, "f").isProperty);

Signatures (experimental):

Signatures are a way to enforce types to comply with other types. For example if you are making a range you can ensure your types conform to a range by mixing in a Models template to the type that needs it. You can also use the utilities provided here to constrain functions to types that adhere to a specific signature.

interface InputRange(T) {
    @property bool empty();
    @property T front();
    @ignoreAttributes void popFront();
}

struct MyRange {
    mixin Models!(InputRange!int);
}

The above will fail to compile with something like:

source/bolts/experimental/signatures.d(310,5): Error: static assert:  "Type MyRange does not comply to signature InputRange!(int)
  Missing identifier empty of type bool.
  Missing identifier front of type int.
  Missing identifier popFront of function void().
  source/bolts/experimental/signatures.d(464): <-- Signature InputRange!(int) defined here.
  source/bolts/experimental/signatures.d(471): <-- Checked here."

Refraction (experimental):

It is sometimes necessary to create a function which is an exact copy of another function. Or sometimes it is necessary to introduce a few variations, while carrying all the other aspects. Because of function attributes, parameter storage classes and user-defined attributes, this requires building a string mixin. In addition, the mixed-in code must refer only to local names, if it is to work across module boundaires. This module facilitates the creation of such mixins.

For example, this creates a function that has a different name and return type, but retains the 'pure' attribute from the original function:

pure int answer() { return 42; }
mixin(
  refract!(answer, "answer").withName("realAnswer")
  .withReturnType("real")
  .mixture);
static assert(is(typeof(realAnswer()) == real));
static assert(functionAttributes!realAnswer & FunctionAttribute.pure_);