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// Written in the D programming language.
/**
* This module implements a
* $(LINK2 http://erdani.org/publications/cuj-04-2002.html,discriminated union)
* type (a.k.a.
* $(LINK2 http://en.wikipedia.org/wiki/Tagged_union,tagged union),
* $(LINK2 http://en.wikipedia.org/wiki/Algebraic_data_type,algebraic type)).
* Such types are useful
* for type-uniform binary interfaces, interfacing with scripting
* languages, and comfortable exploratory programming.
*
* Macros:
* WIKI = Phobos/StdVariant
*
* Synopsis:
*
* ----
* Variant a; // Must assign before use, otherwise exception ensues
* // Initialize with an integer; make the type int
* Variant b = 42;
* assert(b.type == typeid(int));
* // Peek at the value
* assert(b.peek!(int) !is null && *b.peek!(int) == 42);
* // Automatically convert per language rules
* auto x = b.get!(real);
* // Assign any other type, including other variants
* a = b;
* a = 3.14;
* assert(a.type == typeid(double));
* // Implicit conversions work just as with built-in types
* assert(a > b);
* // Check for convertibility
* assert(!a.convertsTo!(int)); // double not convertible to int
* // Strings and all other arrays are supported
* a = "now I'm a string";
* assert(a == "now I'm a string");
* a = new int[42]; // can also assign arrays
* assert(a.length == 42);
* a[5] = 7;
* assert(a[5] == 7);
* // Can also assign class values
* class Foo {}
* auto foo = new Foo;
* a = foo;
* assert(*a.peek!(Foo) == foo); // and full type information is preserved
* ----
*
* Credits:
*
* Reviewed by Brad Roberts. Daniel Keep provided a detailed code
* review prompting the following improvements: (1) better support for
* arrays; (2) support for associative arrays; (3) friendlier behavior
* towards the garbage collector.
*
* Copyright: Copyright Andrei Alexandrescu 2007 - 2009.
* License: <a href="http://www.boost.org/LICENSE_1_0.txt">Boost License 1.0</a>.
* Authors: $(WEB erdani.org, Andrei Alexandrescu)
* Source: $(PHOBOSSRC std/_variant.d)
*/
/* Copyright Andrei Alexandrescu 2007 - 2009.
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*/
module std.variant;
import std.traits, std.c.string, std.typetuple, std.conv, std.exception;
@trusted:
private template maxSize(T...)
{
static if (T.length == 1)
{
enum size_t maxSize = T[0].sizeof;
}
else
{
enum size_t maxSize = T[0].sizeof >= maxSize!(T[1 .. $])
? T[0].sizeof : maxSize!(T[1 .. $]);
}
}
struct This;
template AssociativeArray(T)
{
enum bool valid = false;
alias void Key;
alias void Value;
}
template AssociativeArray(T : V[K], K, V)
{
enum bool valid = true;
alias K Key;
alias V Value;
}
template This2Variant(V, T...)
{
static if (T.length == 0) alias TypeTuple!() This2Variant;
else static if (is(AssociativeArray!(T[0]).Key == This))
{
static if (is(AssociativeArray!(T[0]).Value == This))
alias TypeTuple!(V[V],
This2Variant!(V, T[1 .. $])) This2Variant;
else
alias TypeTuple!(AssociativeArray!(T[0]).Value[V],
This2Variant!(V, T[1 .. $])) This2Variant;
}
else static if (is(AssociativeArray!(T[0]).Value == This))
alias TypeTuple!(V[AssociativeArray!(T[0]).Key],
This2Variant!(V, T[1 .. $])) This2Variant;
else static if (is(T[0] == This[]))
alias TypeTuple!(V[], This2Variant!(V, T[1 .. $])) This2Variant;
else static if (is(T[0] == This*))
alias TypeTuple!(V*, This2Variant!(V, T[1 .. $])) This2Variant;
else
alias TypeTuple!(T[0], This2Variant!(V, T[1 .. $])) This2Variant;
}
/**
* $(D_PARAM VariantN) is a back-end type seldom used directly by user
* code. Two commonly-used types using $(D_PARAM VariantN) as
* back-end are:
*
* $(OL $(LI $(B Algebraic): A closed discriminated union with a
* limited type universe (e.g., $(D_PARAM Algebraic!(int, double,
* string)) only accepts these three types and rejects anything
* else).) $(LI $(B Variant): An open discriminated union allowing an
* unbounded set of types. The restriction is that the size of the
* stored type cannot be larger than the largest built-in type. This
* means that $(D_PARAM Variant) can accommodate all primitive types
* and all user-defined types except for large $(D_PARAM struct)s.) )
*
* Both $(D_PARAM Algebraic) and $(D_PARAM Variant) share $(D_PARAM
* VariantN)'s interface. (See their respective documentations below.)
*
* $(D_PARAM VariantN) is a discriminated union type parameterized
* with the largest size of the types stored ($(D_PARAM maxDataSize))
* and with the list of allowed types ($(D_PARAM AllowedTypes)). If
* the list is empty, then any type up of size up to $(D_PARAM
* maxDataSize) (rounded up for alignment) can be stored in a
* $(D_PARAM VariantN) object.
*
*/
struct VariantN(size_t maxDataSize, AllowedTypesX...)
{
alias This2Variant!(VariantN, AllowedTypesX) AllowedTypes;
private:
// Compute the largest practical size from maxDataSize
struct SizeChecker
{
int function() fptr;
ubyte[maxDataSize] data;
}
enum size = SizeChecker.sizeof - (int function()).sizeof;
static assert(size >= (void*).sizeof);
/** Tells whether a type $(D_PARAM T) is statically allowed for
* storage inside a $(D_PARAM VariantN) object by looking
* $(D_PARAM T) up in $(D_PARAM AllowedTypes). If $(D_PARAM
* AllowedTypes) is empty, all types of size up to $(D_PARAM
* maxSize) are allowed.
*/
public template allowed(T)
{
enum bool allowed
= is(T == VariantN)
||
//T.sizeof <= size &&
(AllowedTypes.length == 0 || staticIndexOf!(T, AllowedTypes) >= 0);
}
// Each internal operation is encoded with an identifier. See
// the "handler" function below.
enum OpID { getTypeInfo, get, compare, testConversion, toString,
index, indexAssign, catAssign, copyOut, length,
apply }
// state
ptrdiff_t function(OpID selector, ubyte[size]* store, void* data) fptr
= &handler!(void);
union
{
ubyte[size] store;
// conservatively mark the region as pointers
static if (size >= (void*).sizeof)
void* p[size / (void*).sizeof];
}
// internals
// Handler for an uninitialized value
static ptrdiff_t handler(A : void)(OpID selector, ubyte[size]*, void* parm)
{
switch (selector)
{
case OpID.getTypeInfo:
*cast(TypeInfo *) parm = typeid(A);
break;
case OpID.copyOut:
auto target = cast(VariantN *) parm;
target.fptr = &handler!(A);
// no need to copy the data (it's garbage)
break;
case OpID.compare:
auto rhs = cast(VariantN *) parm;
return rhs.peek!(A)
? 0 // all uninitialized are equal
: ptrdiff_t.min; // uninitialized variant is not comparable otherwise
case OpID.toString:
string * target = cast(string*) parm;
*target = "<Uninitialized VariantN>";
break;
case OpID.get:
case OpID.testConversion:
case OpID.index:
case OpID.indexAssign:
case OpID.catAssign:
case OpID.length:
throw new VariantException(
"Attempt to use an uninitialized VariantN");
default: assert(false, "Invalid OpID");
}
return 0;
}
// Handler for all of a type's operations
static ptrdiff_t handler(A)(OpID selector, ubyte[size]* pStore, void* parm)
{
static A* getPtr(void* untyped)
{
if (untyped)
{
static if (A.sizeof <= size)
return cast(A*) untyped;
else
return *cast(A**) untyped;
}
return null;
}
auto zis = getPtr(pStore);
// Input: TypeInfo object
// Output: target points to a copy of *me, if me was not null
// Returns: true iff the A can be converted to the type represented
// by the incoming TypeInfo
static bool tryPutting(A* src, TypeInfo targetType, void* target)
{
alias TypeTuple!(A, ImplicitConversionTargets!A) AllTypes;
foreach (T ; AllTypes)
{
if (targetType != typeid(T) &&
targetType != typeid(const(T)))
{
static if (isImplicitlyConvertible!(T, immutable(T)))
{
if (targetType != typeid(immutable(T)))
{
continue;
}
}
else
{
continue;
}
}
// found!!!
static if (is(typeof(*cast(T*) target = *src)))
{
auto zat = cast(T*) target;
if (src)
{
assert(target, "target must be non-null");
*zat = *src;
}
}
else
{
// type is not assignable
if (src) assert(false, A.stringof);
}
return true;
}
return false;
}
switch (selector)
{
case OpID.getTypeInfo:
*cast(TypeInfo *) parm = typeid(A);
break;
case OpID.copyOut:
auto target = cast(VariantN *) parm;
assert(target);
tryPutting(zis, typeid(A), cast(void*) getPtr(&target.store))
|| assert(false);
target.fptr = &handler!(A);
break;
case OpID.get:
return !tryPutting(zis, *cast(TypeInfo*) parm, parm);
case OpID.testConversion:
return !tryPutting(null, *cast(TypeInfo*) parm, null);
case OpID.compare:
auto rhsP = cast(VariantN *) parm;
auto rhsType = rhsP.type;
// Are we the same?
if (rhsType == typeid(A))
{
// cool! Same type!
auto rhsPA = getPtr(&rhsP.store);
static if (is(typeof(A.init == A.init)))
{
if (*rhsPA == *zis)
{
return 0;
}
static if (is(typeof(A.init < A.init)))
{
return *zis < *rhsPA ? -1 : 1;
}
else
{
// Not equal, and type does not support ordering
// comparisons.
return ptrdiff_t.min;
}
}
else
{
// Type does not support comparisons at all.
return ptrdiff_t.min;
}
} else if (rhsType == typeid(void))
{
// No support for ordering comparisons with
// uninitialized vars
return ptrdiff_t.min;
}
VariantN temp;
// Do I convert to rhs?
if (tryPutting(zis, rhsType, &temp.store))
{
// cool, I do; temp's store contains my data in rhs's type!
// also fix up its fptr
temp.fptr = rhsP.fptr;
// now lhsWithRhsType is a full-blown VariantN of rhs's type
return temp.opCmp(*rhsP);
}
// Does rhs convert to zis?
*cast(TypeInfo*) &temp.store = typeid(A);
if (rhsP.fptr(OpID.get, &rhsP.store, &temp.store) == 0)
{
// cool! Now temp has rhs in my type!
auto rhsPA = getPtr(&temp.store);
static if (is(typeof(A.init == A.init)))
{
if (*rhsPA == *zis)
{
return 0;
}
static if (is(typeof(A.init < A.init)))
{
return *zis < *rhsPA ? -1 : 1;
}
else
{
// Not equal, and type does not support ordering
// comparisons.
return ptrdiff_t.min;
}
}
else
{
// Type does not support comparisons at all.
return ptrdiff_t.min;
}
}
return ptrdiff_t.min; // dunno
case OpID.toString:
auto target = cast(string*) parm;
static if (is(typeof(to!(string)(*zis))))
{
*target = to!(string)(*zis);
break;
}
// TODO: The following test evaluates to true for shared objects.
// Use __traits for now until this is sorted out.
// else static if (is(typeof((*zis).toString)))
else static if (__traits(compiles, {(*zis).toString();}))
{
*target = (*zis).toString();
break;
}
else
{
throw new VariantException(typeid(A), typeid(string));
}
case OpID.index:
// Added allowed!(...) prompted by a bug report by Chris
// Nicholson-Sauls.
static if (isStaticArray!(A) && allowed!(typeof(A.init)))
{
enforce(0, "Not implemented");
}
static if (isDynamicArray!(A) && allowed!(typeof(A.init[0])))
{
// array type; input and output are the same VariantN
auto result = cast(VariantN*) parm;
size_t index = result.convertsTo!(int)
? result.get!(int) : result.get!(size_t);
*result = (*zis)[index];
break;
}
else static if (isAssociativeArray!(A)
&& allowed!(typeof(A.init.values[0])))
{
auto result = cast(VariantN*) parm;
*result = (*zis)[result.get!(typeof(A.keys[0]))];
break;
}
else
{
throw new VariantException(typeid(A), typeid(void[]));
}
case OpID.indexAssign:
static if (isArray!(A) && is(typeof((*zis)[0] = (*zis)[0])))
{
// array type; result comes first, index comes second
auto args = cast(VariantN*) parm;
size_t index = args[1].convertsTo!(int)
? args[1].get!(int) : args[1].get!(size_t);
(*zis)[index] = args[0].get!(typeof((*zis)[0]));
break;
}
else static if (isAssociativeArray!(A))
{
auto args = cast(VariantN*) parm;
(*zis)[args[1].get!(typeof(A.keys[0]))]
= args[0].get!(typeof(A.values[0]));
break;
}
else
{
throw new VariantException(typeid(A), typeid(void[]));
}
case OpID.catAssign:
static if (is(typeof((*zis)[0])) && is(typeof((*zis) ~= *zis)))
{
// array type; parm is the element to append
auto arg = cast(VariantN*) parm;
alias typeof((*zis)[0]) E;
if (arg[0].convertsTo!(E))
{
// append one element to the array
(*zis) ~= [ arg[0].get!(E) ];
}
else
{
// append a whole array to the array
(*zis) ~= arg[0].get!(A);
}
break;
}
else
{
throw new VariantException(typeid(A), typeid(void[]));
}
case OpID.length:
static if (is(typeof(zis.length)))
{
return zis.length;
}
else
{
throw new VariantException(typeid(A), typeid(void[]));
}
case OpID.apply:
assert(0);
default: assert(false);
}
return 0;
}
public:
/** Constructs a $(D_PARAM VariantN) value given an argument of a
* generic type. Statically rejects disallowed types.
*/
this(T)(T value)
{
static assert(allowed!(T), "Cannot store a " ~ T.stringof
~ " in a " ~ VariantN.stringof);
opAssign(value);
}
/** Assigns a $(D_PARAM VariantN) from a generic
* argument. Statically rejects disallowed types. */
VariantN opAssign(T)(T rhs)
{
//writeln(typeid(rhs));
static assert(allowed!(T), "Cannot store a " ~ T.stringof
~ " in a " ~ VariantN.stringof ~ ". Valid types are "
~ AllowedTypes.stringof);
static if (is(T : VariantN))
{
rhs.fptr(OpID.copyOut, &rhs.store, &this);
}
else static if (is(T : const(VariantN)))
{
static assert(false,
"Assigning Variant objects from const Variant"
" objects is currently not supported.");
}
else
{
static if (T.sizeof <= size)
{
// If T is a class we're only copying the reference, so it
// should be safe to cast away shared so the memcpy will work.
//
// TODO: If a shared class has an atomic reference then using
// an atomic load may be more correct. Just make sure
// to use the fastest approach for the load op.
static if (is(T == class) && is(T == shared))
memcpy(&store, cast(const(void*)) &rhs, rhs.sizeof);
else
memcpy(&store, &rhs, rhs.sizeof);
}
else
{
static if (__traits(compiles, {new T(rhs);}))
{
auto p = new T(rhs);
}
else
{
auto p = new T;
*p = rhs;
}
memcpy(&store, &p, p.sizeof);
}
fptr = &handler!(T);
}
return this;
}
/** Returns true if and only if the $(D_PARAM VariantN) object
* holds a valid value (has been initialized with, or assigned
* from, a valid value).
* Example:
* ----
* Variant a;
* assert(!a.hasValue);
* Variant b;
* a = b;
* assert(!a.hasValue); // still no value
* a = 5;
* assert(a.hasValue);
* ----
*/
@property bool hasValue() const pure nothrow
{
// @@@BUG@@@ in compiler, the cast shouldn't be needed
return cast(typeof(&handler!(void))) fptr != &handler!(void);
}
/**
* If the $(D_PARAM VariantN) object holds a value of the
* $(I exact) type $(D_PARAM T), returns a pointer to that
* value. Otherwise, returns $(D_PARAM null). In cases
* where $(D_PARAM T) is statically disallowed, $(D_PARAM
* peek) will not compile.
*
* Example:
* ----
* Variant a = 5;
* auto b = a.peek!(int);
* assert(b !is null);
* *b = 6;
* assert(a == 6);
* ----
*/
@property T * peek(T)()
{
static if (!is(T == void))
static assert(allowed!(T), "Cannot store a " ~ T.stringof
~ " in a " ~ VariantN.stringof);
return type == typeid(T) ? cast(T*) &store : null;
}
/**
* Returns the $(D_PARAM typeid) of the currently held value.
*/
@property TypeInfo type() const
{
TypeInfo result;
fptr(OpID.getTypeInfo, null, &result);
return result;
}
/**
* Returns $(D_PARAM true) if and only if the $(D_PARAM VariantN)
* object holds an object implicitly convertible to type $(D_PARAM
* U). Implicit convertibility is defined as per
* $(LINK2 std_traits.html#ImplicitConversionTargets,ImplicitConversionTargets).
*/
@property bool convertsTo(T)() const
{
TypeInfo info = typeid(T);
return fptr(OpID.testConversion, null, &info) == 0;
}
// private T[] testing123(T)(T*);
// /**
// * A workaround for the fact that functions cannot return
// * statically-sized arrays by value. Essentially $(D_PARAM
// * DecayStaticToDynamicArray!(T[N])) is an alias for $(D_PARAM
// * T[]) and $(D_PARAM DecayStaticToDynamicArray!(T)) is an alias
// * for $(D_PARAM T).
// */
// template DecayStaticToDynamicArray(T)
// {
// static if (isStaticArray!(T))
// {
// alias typeof(testing123(&T[0])) DecayStaticToDynamicArray;
// }
// else
// {
// alias T DecayStaticToDynamicArray;
// }
// }
// static assert(is(DecayStaticToDynamicArray!(immutable(char)[21]) ==
// immutable(char)[]),
// DecayStaticToDynamicArray!(immutable(char)[21]).stringof);
/**
* Returns the value stored in the $(D_PARAM VariantN) object,
* implicitly converted to the requested type $(D_PARAM T), in
* fact $(D_PARAM DecayStaticToDynamicArray!(T)). If an implicit
* conversion is not possible, throws a $(D_PARAM
* VariantException).
*/
@property T get(T)() if (!is(T == const))
{
union Buf
{
TypeInfo info;
T result;
}
auto p = *cast(T**) &store;
Buf buf = { typeid(T) };
if (fptr(OpID.get, &store, &buf))
{
throw new VariantException(type, typeid(T));
}
return buf.result;
}
@property T get(T)() const if (is(T == const))
{
union Buf
{
TypeInfo info;
Unqual!T result;
}
auto p = *cast(T**) &store;
Buf buf = { typeid(T) };
if (fptr(OpID.get, cast(ubyte[size]*) &store, &buf))
{
throw new VariantException(type, typeid(T));
}
return buf.result;
}
/**
* Returns the value stored in the $(D_PARAM VariantN) object,
* explicitly converted (coerced) to the requested type $(D_PARAM
* T). If $(D_PARAM T) is a string type, the value is formatted as
* a string. If the $(D_PARAM VariantN) object is a string, a
* parse of the string to type $(D_PARAM T) is attempted. If a
* conversion is not possible, throws a $(D_PARAM
* VariantException).
*/
@property T coerce(T)()
{
static if (isNumeric!(T))
{
if (convertsTo!real)
{
// maybe optimize this fella; handle ints separately
return to!T(get!real);
}
else if (convertsTo!(const(char)[]))
{
return to!T(get!(const(char)[]));
}
// I'm not sure why this doesn't convert to const(char),
// but apparently it doesn't (probably a deeper bug).
//
// Until that is fixed, this quick addition keeps a common
// function working. "10".coerce!int ought to work.
else if (convertsTo!(immutable(char)[]))
{
return to!T(get!(immutable(char)[]));
}
else
{
enforce(false, text("Type ", type, " does not convert to ",
typeid(T)));
assert(0);
}
}
else static if (is(T : Object))
{
return to!(T)(get!(Object));
}
else static if (isSomeString!(T))
{
return to!(T)(toString());
}
else
{
// Fix for bug 1649
static assert(false, "unsupported type for coercion");
}
}
// testing the string coerce
unittest
{
Variant a = "10";
assert(a.coerce!int == 10);
}
/**
* Formats the stored value as a string.
*/
string toString()
{
string result;
fptr(OpID.toString, &store, &result) == 0 || assert(false);
return result;
}
/**
* Comparison for equality used by the "==" and "!=" operators.
*/
// returns 1 if the two are equal
bool opEquals(T)(T rhs)
{
static if (is(T == VariantN))
alias rhs temp;
else
auto temp = VariantN(rhs);
return fptr(OpID.compare, &store, &temp) == 0;
}
/**
* Ordering comparison used by the "<", "<=", ">", and ">="
* operators. In case comparison is not sensible between the held
* value and $(D_PARAM rhs), an exception is thrown.
*/
int opCmp(T)(T rhs)
{
static if (is(T == VariantN))
alias rhs temp;
else
auto temp = VariantN(rhs);
auto result = fptr(OpID.compare, &store, &temp);
if (result == ptrdiff_t.min)
{
throw new VariantException(type, temp.type);
}
assert(result >= -1 && result <= 1); // Should be true for opCmp.
return cast(int) result;
}
/**
* Computes the hash of the held value.
*/
size_t toHash()
{
return type.getHash(&store);
}
private VariantN opArithmetic(T, string op)(T other)
{
VariantN result;
static if (is(T == VariantN))
{
if (convertsTo!(uint) && other.convertsTo!(uint))
result = mixin("get!(uint) " ~ op ~ " other.get!(uint)");
else if (convertsTo!(int) && other.convertsTo!(int))
result = mixin("get!(int) " ~ op ~ " other.get!(int)");
else if (convertsTo!(ulong) && other.convertsTo!(ulong))
result = mixin("get!(ulong) " ~ op ~ " other.get!(ulong)");
else if (convertsTo!(long) && other.convertsTo!(long))
result = mixin("get!(long) " ~ op ~ " other.get!(long)");
else if (convertsTo!(float) && other.convertsTo!(float))
result = mixin("get!(float) " ~ op ~ " other.get!(float)");
else if (convertsTo!(double) && other.convertsTo!(double))
result = mixin("get!(double) " ~ op ~ " other.get!(double)");
else
result = mixin("get!(real) " ~ op ~ " other.get!(real)");
}
else
{
if (is(typeof(T.max) : uint) && T.min == 0 && convertsTo!(uint))
result = mixin("get!(uint) " ~ op ~ " other");
else if (is(typeof(T.max) : int) && T.min < 0 && convertsTo!(int))
result = mixin("get!(int) " ~ op ~ " other");
else if (is(typeof(T.max) : ulong) && T.min == 0
&& convertsTo!(ulong))
result = mixin("get!(ulong) " ~ op ~ " other");
else if (is(typeof(T.max) : long) && T.min < 0 && convertsTo!(long))
result = mixin("get!(long) " ~ op ~ " other");
else if (is(T : float) && convertsTo!(float))
result = mixin("get!(float) " ~ op ~ " other");
else if (is(T : double) && convertsTo!(double))
result = mixin("get!(double) " ~ op ~ " other");
else
result = mixin("get!(real) " ~ op ~ " other");
}
return result;
}
private VariantN opLogic(T, string op)(T other)
{
VariantN result;
static if (is(T == VariantN))
{
if (convertsTo!(uint) && other.convertsTo!(uint))
result = mixin("get!(uint) " ~ op ~ " other.get!(uint)");
else if (convertsTo!(int) && other.convertsTo!(int))
result = mixin("get!(int) " ~ op ~ " other.get!(int)");
else if (convertsTo!(ulong) && other.convertsTo!(ulong))
result = mixin("get!(ulong) " ~ op ~ " other.get!(ulong)");
else
result = mixin("get!(long) " ~ op ~ " other.get!(long)");
}
else
{
if (is(typeof(T.max) : uint) && T.min == 0 && convertsTo!(uint))
result = mixin("get!(uint) " ~ op ~ " other");
else if (is(typeof(T.max) : int) && T.min < 0 && convertsTo!(int))
result = mixin("get!(int) " ~ op ~ " other");
else if (is(typeof(T.max) : ulong) && T.min == 0
&& convertsTo!(ulong))
result = mixin("get!(ulong) " ~ op ~ " other");
else
result = mixin("get!(long) " ~ op ~ " other");
}
return result;
}
/**
* Arithmetic between $(D_PARAM VariantN) objects and numeric
* values. All arithmetic operations return a $(D_PARAM VariantN)
* object typed depending on the types of both values
* involved. The conversion rules mimic D's built-in rules for
* arithmetic conversions.
*/
// Adapted from http://www.prowiki.org/wiki4d/wiki.cgi?DanielKeep/Variant
// arithmetic
VariantN opAdd(T)(T rhs) { return opArithmetic!(T, "+")(rhs); }
///ditto
VariantN opSub(T)(T rhs) { return opArithmetic!(T, "-")(rhs); }
// Commenteed all _r versions for now because of ambiguities
// arising when two Variants are used
/////ditto
// VariantN opSub_r(T)(T lhs)
// {
// return VariantN(lhs).opArithmetic!(VariantN, "-")(this);
// }
///ditto
VariantN opMul(T)(T rhs) { return opArithmetic!(T, "*")(rhs); }
///ditto
VariantN opDiv(T)(T rhs) { return opArithmetic!(T, "/")(rhs); }
// ///ditto
// VariantN opDiv_r(T)(T lhs)
// {
// return VariantN(lhs).opArithmetic!(VariantN, "/")(this);
// }
///ditto
VariantN opMod(T)(T rhs) { return opArithmetic!(T, "%")(rhs); }
// ///ditto
// VariantN opMod_r(T)(T lhs)
// {
// return VariantN(lhs).opArithmetic!(VariantN, "%")(this);
// }
///ditto
VariantN opAnd(T)(T rhs) { return opLogic!(T, "&")(rhs); }
///ditto
VariantN opOr(T)(T rhs) { return opLogic!(T, "|")(rhs); }
///ditto
VariantN opXor(T)(T rhs) { return opLogic!(T, "^")(rhs); }
///ditto
VariantN opShl(T)(T rhs) { return opLogic!(T, "<<")(rhs); }
// ///ditto
// VariantN opShl_r(T)(T lhs)
// {
// return VariantN(lhs).opLogic!(VariantN, "<<")(this);
// }
///ditto
VariantN opShr(T)(T rhs) { return opLogic!(T, ">>")(rhs); }
// ///ditto
// VariantN opShr_r(T)(T lhs)
// {
// return VariantN(lhs).opLogic!(VariantN, ">>")(this);
// }
///ditto
VariantN opUShr(T)(T rhs) { return opLogic!(T, ">>>")(rhs); }
// ///ditto
// VariantN opUShr_r(T)(T lhs)
// {
// return VariantN(lhs).opLogic!(VariantN, ">>>")(this);
// }
///ditto
VariantN opCat(T)(T rhs)
{
auto temp = this;
temp ~= rhs;
return temp;
}
// ///ditto
// VariantN opCat_r(T)(T rhs)
// {
// VariantN temp = rhs;
// temp ~= this;
// return temp;
// }
///ditto
VariantN opAddAssign(T)(T rhs) { return this = this + rhs; }
///ditto
VariantN opSubAssign(T)(T rhs) { return this = this - rhs; }
///ditto
VariantN opMulAssign(T)(T rhs) { return this = this * rhs; }
///ditto
VariantN opDivAssign(T)(T rhs) { return this = this / rhs; }
///ditto
VariantN opModAssign(T)(T rhs) { return this = this % rhs; }
///ditto
VariantN opAndAssign(T)(T rhs) { return this = this & rhs; }
///ditto
VariantN opOrAssign(T)(T rhs) { return this = this | rhs; }
///ditto
VariantN opXorAssign(T)(T rhs) { return this = this ^ rhs; }
///ditto
VariantN opShlAssign(T)(T rhs) { return this = this << rhs; }
///ditto
VariantN opShrAssign(T)(T rhs) { return this = this >> rhs; }
///ditto
VariantN opUShrAssign(T)(T rhs) { return this = this >>> rhs; }
///ditto
VariantN opCatAssign(T)(T rhs)
{
auto toAppend = VariantN(rhs);
fptr(OpID.catAssign, &store, &toAppend) == 0 || assert(false);
return this;
}
/**
* Array and associative array operations. If a $(D_PARAM
* VariantN) contains an (associative) array, it can be indexed
* into. Otherwise, an exception is thrown.
*
* Example:
* ----
* auto a = Variant(new int[10]);
* a[5] = 42;
* assert(a[5] == 42);
* int[int] hash = [ 42:24 ];
* a = hash;
* assert(a[42] == 24);
* ----
*
* Caveat:
*
* Due to limitations in current language, read-modify-write
* operations $(D_PARAM op=) will not work properly:
*
* ----
* Variant a = new int[10];
* a[5] = 42;
* a[5] += 8;
* assert(a[5] == 50); // fails, a[5] is still 42
* ----
*/
VariantN opIndex(K)(K i)
{
auto result = VariantN(i);
fptr(OpID.index, &store, &result) == 0 || assert(false);
return result;
}
unittest
{
int[int] hash = [ 42:24 ];
Variant v = hash;
assert(v[42] == 24);
v[42] = 5;
assert(v[42] == 5);
}
/// ditto
VariantN opIndexAssign(T, N)(T value, N i)
{
VariantN[2] args = [ VariantN(value), VariantN(i) ];
fptr(OpID.indexAssign, &store, &args) == 0 || assert(false);
return args[0];
}
/** If the $(D_PARAM VariantN) contains an (associative) array,
* returns the length of that array. Otherwise, throws an
* exception.
*/
@property size_t length()
{
return cast(size_t) fptr(OpID.length, &store, null);
}
/**
If the $(D VariantN) contains an array, applies $(D dg) to each
element of the array in turn. Otherwise, throws an exception.
*/
int opApply(Delegate)(scope Delegate dg) if (is(Delegate == delegate))
{
alias ParameterTypeTuple!(Delegate)[0] A;
if (type == typeid(A[]))
{
auto arr = get!(A[]);
foreach (ref e; arr)
{
if (dg(e)) return 1;
}
}
else static if (is(A == VariantN))
{
foreach (i; 0 .. length)
{
// @@@TODO@@@: find a better way to not confuse
// clients who think they change values stored in the
// Variant when in fact they are only changing tmp.
auto tmp = this[i];
debug scope(exit) assert(tmp == this[i]);
if (dg(tmp)) return 1;
}
}
else
{
enforce(false, text("Variant type ", type,
" not iterable with values of type ",
A.stringof));
}
return 0;
}
}
//Issue# 8195
unittest
{
struct S
{
int a;
long b;
string c;
real d;
bool e;
}
static assert(S.sizeof >= Variant.sizeof);
alias TypeTuple!(string, int, S) Types;
alias VariantN!(maxSize!Types, Types) MyVariant;
auto v = MyVariant(S.init);
assert(v == S.init);
}
/**
* Algebraic data type restricted to a closed set of possible
* types. It's an alias for a $(D_PARAM VariantN) with an
* appropriately-constructed maximum size. $(D_PARAM Algebraic) is
* useful when it is desirable to restrict what a discriminated type
* could hold to the end of defining simpler and more efficient
* manipulation.
*
* Future additions to $(D_PARAM Algebraic) will allow compile-time
* checking that all possible types are handled by user code,
* eliminating a large class of errors.
*
* Bugs:
*
* Currently, $(D_PARAM Algebraic) does not allow recursive data
* types. They will be allowed in a future iteration of the
* implementation.
*
* Example:
* ----
* auto v = Algebraic!(int, double, string)(5);
* assert(v.peek!(int));
* v = 3.14;
* assert(v.peek!(double));
* // auto x = v.peek!(long); // won't compile, type long not allowed
* // v = '1'; // won't compile, type char not allowed
* ----
*/
template Algebraic(T...)
{
alias VariantN!(maxSize!(T), T) Algebraic;
}
/**
$(D_PARAM Variant) is an alias for $(D_PARAM VariantN) instantiated
with the largest of $(D_PARAM creal), $(D_PARAM char[]), and $(D_PARAM
void delegate()). This ensures that $(D_PARAM Variant) is large enough
to hold all of D's predefined types, including all numeric types,
pointers, delegates, and class references. You may want to use
$(D_PARAM VariantN) directly with a different maximum size either for
storing larger types, or for saving memory.
*/
alias VariantN!(maxSize!(creal, char[], void delegate())) Variant;
/**
* Returns an array of variants constructed from $(D_PARAM args).
* Example:
* ----
* auto a = variantArray(1, 3.14, "Hi!");
* assert(a[1] == 3.14);
* auto b = Variant(a); // variant array as variant
* assert(b[1] == 3.14);
* ----
*
* Code that needs functionality similar to the $(D_PARAM boxArray)
* function in the $(D_PARAM std.boxer) module can achieve it like this:
*
* ----
* // old
* Box[] fun(...)
* {
* ...
* return boxArray(_arguments, _argptr);
* }
* // new
* Variant[] fun(T...)(T args)
* {
* ...
* return variantArray(args);
* }
* ----
*
* This is by design. During construction the $(D_PARAM Variant) needs
* static type information about the type being held, so as to store a
* pointer to function for fast retrieval.
*/
Variant[] variantArray(T...)(T args)
{
Variant[] result;
foreach (arg; args)
{
result ~= Variant(arg);
}
return result;
}
/**
* Thrown in three cases:
*
* $(OL $(LI An uninitialized Variant is used in any way except
* assignment and $(D_PARAM hasValue);) $(LI A $(D_PARAM get) or
* $(D_PARAM coerce) is attempted with an incompatible target type;)
* $(LI A comparison between $(D_PARAM Variant) objects of
* incompatible types is attempted.))
*
*/
// @@@ BUG IN COMPILER. THE 'STATIC' BELOW SHOULD NOT COMPILE
static class VariantException : Exception
{
/// The source type in the conversion or comparison
TypeInfo source;
/// The target type in the conversion or comparison
TypeInfo target;
this(string s)
{
super(s);
}
this(TypeInfo source, TypeInfo target)
{
super("Variant: attempting to use incompatible types "
~ source.toString()
~ " and " ~ target.toString());
this.source = source;
this.target = target;
}
}
unittest
{
alias This2Variant!(char, int, This[int]) W1;
alias TypeTuple!(int, char[int]) W2;
static assert(is(W1 == W2));
alias Algebraic!(void, string) var_t;
var_t foo = "quux";
}
unittest
{
// @@@BUG@@@
// alias Algebraic!(real, This[], This[int], This[This]) A;
// A v1, v2, v3;
// v2 = 5.0L;
// v3 = 42.0L;
// //v1 = [ v2 ][];
// auto v = v1.peek!(A[]);
// //writeln(v[0]);
// v1 = [ 9 : v3 ];
// //writeln(v1);
// v1 = [ v3 : v3 ];
// //writeln(v1);
}
unittest
{
// try it with an oddly small size
VariantN!(1) test;
assert(test.size > 1);
// variantArray tests
auto heterogeneous = variantArray(1, 4.5, "hi");
assert(heterogeneous.length == 3);
auto variantArrayAsVariant = Variant(heterogeneous);
assert(variantArrayAsVariant[0] == 1);
assert(variantArrayAsVariant.length == 3);
// array tests
auto arr = Variant([1.2].dup);
auto e = arr[0];
assert(e == 1.2);
arr[0] = 2.0;
assert(arr[0] == 2);
arr ~= 4.5;
assert(arr[1] == 4.5);
// general tests
Variant a;
auto b = Variant(5);
assert(!b.peek!(real) && b.peek!(int));
// assign
a = *b.peek!(int);
// comparison
assert(a == b, a.type.toString() ~ " " ~ b.type.toString());
auto c = Variant("this is a string");
assert(a != c);
// comparison via implicit conversions
a = 42; b = 42.0; assert(a == b);
// try failing conversions
bool failed = false;
try
{
auto d = c.get!(int);
}
catch (Exception e)
{
//writeln(stderr, e.toString);
failed = true;
}
assert(failed); // :o)
// toString tests
a = Variant(42); assert(a.toString() == "42");
a = Variant(42.22); assert(a.toString() == "42.22");
// coerce tests
a = Variant(42.22); assert(a.coerce!(int) == 42);
a = cast(short) 5; assert(a.coerce!(double) == 5);
// Object tests
class B1 {}
class B2 : B1 {}
a = new B2;
assert(a.coerce!(B1) !is null);
a = new B1;
// BUG: I can't get the following line to pass:
// assert(collectException(a.coerce!(B2) is null));
a = cast(Object) new B2; // lose static type info; should still work
assert(a.coerce!(B2) !is null);
// struct Big { int a[45]; }
// a = Big.init;
// hash
assert(a.toHash() != 0);
}
// tests adapted from
// http://www.dsource.org/projects/tango/browser/trunk/tango/core/Variant.d?rev=2601
unittest
{
Variant v;
assert(!v.hasValue);
v = 42;
assert( v.peek!(int) );
assert( v.convertsTo!(long) );
assert( v.get!(int) == 42 );
assert( v.get!(long) == 42L );
assert( v.get!(ulong) == 42uL );
// should be string... @@@BUG IN COMPILER
v = "Hello, World!"c;
assert( v.peek!(string) );
assert( v.get!(string) == "Hello, World!" );
assert(!is(char[] : wchar[]));
assert( !v.convertsTo!(wchar[]) );
assert( v.get!(string) == "Hello, World!" );
// Literal arrays are dynamically-typed
v = cast(int[5]) [1,2,3,4,5];
assert( v.peek!(int[5]) );
assert( v.get!(int[5]) == [1,2,3,4,5] );
{
// @@@BUG@@@: array literals should have type T[], not T[5] (I guess)
// v = [1,2,3,4,5];
// assert( v.peek!(int[]) );
// assert( v.get!(int[]) == [1,2,3,4,5] );
}
v = 3.1413;
assert( v.peek!(double) );
assert( v.convertsTo!(real) );
//@@@ BUG IN COMPILER: DOUBLE SHOULD NOT IMPLICITLY CONVERT TO FLOAT
assert( !v.convertsTo!(float) );
assert( *v.peek!(double) == 3.1413 );
auto u = Variant(v);
assert( u.peek!(double) );
assert( *u.peek!(double) == 3.1413 );
// operators
v = 38;
assert( v + 4 == 42 );
assert( 4 + v == 42 );
assert( v - 4 == 34 );
assert( Variant(4) - v == -34 );
assert( v * 2 == 76 );
assert( 2 * v == 76 );
assert( v / 2 == 19 );
assert( Variant(2) / v == 0 );
assert( v % 2 == 0 );
assert( Variant(2) % v == 2 );
assert( (v & 6) == 6 );
assert( (6 & v) == 6 );
assert( (v | 9) == 47 );
assert( (9 | v) == 47 );
assert( (v ^ 5) == 35 );
assert( (5 ^ v) == 35 );
assert( v << 1 == 76 );
assert( Variant(1) << Variant(2) == 4 );
assert( v >> 1 == 19 );
assert( Variant(4) >> Variant(2) == 1 );
assert( Variant("abc") ~ "def" == "abcdef" );
assert( Variant("abc") ~ Variant("def") == "abcdef" );
v = 38;
v += 4;
assert( v == 42 );
v = 38; v -= 4; assert( v == 34 );
v = 38; v *= 2; assert( v == 76 );
v = 38; v /= 2; assert( v == 19 );
v = 38; v %= 2; assert( v == 0 );
v = 38; v &= 6; assert( v == 6 );
v = 38; v |= 9; assert( v == 47 );
v = 38; v ^= 5; assert( v == 35 );
v = 38; v <<= 1; assert( v == 76 );
v = 38; v >>= 1; assert( v == 19 );
v = 38; v += 1; assert( v < 40 );
v = "abc";
v ~= "def";
assert( v == "abcdef", *v.peek!(char[]) );
assert( Variant(0) < Variant(42) );
assert( Variant(42) > Variant(0) );
assert( Variant(42) > Variant(0.1) );
assert( Variant(42.1) > Variant(1) );
assert( Variant(21) == Variant(21) );
assert( Variant(0) != Variant(42) );
assert( Variant("bar") == Variant("bar") );
assert( Variant("foo") != Variant("bar") );
{
auto v1 = Variant(42);
auto v2 = Variant("foo");
auto v3 = Variant(1+2.0i);
int[Variant] hash;
hash[v1] = 0;
hash[v2] = 1;
hash[v3] = 2;
assert( hash[v1] == 0 );
assert( hash[v2] == 1 );
assert( hash[v3] == 2 );
}
/+
// @@@BUG@@@
// dmd: mtype.c:3886: StructDeclaration* TypeAArray::getImpl(): Assertion `impl' failed.
{
int[char[]] hash;
hash["a"] = 1;
hash["b"] = 2;
hash["c"] = 3;
Variant vhash = hash;
assert( vhash.get!(int[char[]])["a"] == 1 );
assert( vhash.get!(int[char[]])["b"] == 2 );
assert( vhash.get!(int[char[]])["c"] == 3 );
}
+/
}
unittest
{
// bug 1558
Variant va=1;
Variant vb=-2;
assert((va+vb).get!(int) == -1);
assert((va-vb).get!(int) == 3);
}
unittest
{
Variant a;
a=5;
Variant b;
b=a;
Variant[] c;
c = variantArray(1, 2, 3.0, "hello", 4);
assert(c[3] == "hello");
}
unittest
{
Variant v = 5;
assert (!__traits(compiles, v.coerce!(bool delegate())));
}
unittest
{
struct Huge {
real a, b, c, d, e, f, g;
}
Huge huge;
huge.e = 42;
Variant v;
v = huge; // Compile time error.
assert(v.get!(Huge).e == 42);
}
unittest
{
const x = Variant(42);
auto y1 = x.get!(const int);
// @@@BUG@@@
//auto y2 = x.get!(immutable int)();
}
// test iteration
unittest
{
auto v = Variant([ 1, 2, 3, 4 ][]);
auto j = 0;
foreach (int i; v)
{
assert(i == ++j);
}
assert(j == 4);
}
// test convertibility
unittest
{
auto v = Variant("abc".dup);
assert(v.convertsTo!(char[]));
}
// http://d.puremagic.com/issues/show_bug.cgi?id=5424
unittest
{
interface A {
void func1();
}
static class AC: A {
void func1() {
}
}
A a = new AC();
a.func1();
Variant b = Variant(a);
}
unittest
{
// bug 7070
Variant v;
v = null;
}
// Ordering comparisons of incompatible types, e.g. issue 7990.
unittest
{
assertThrown!VariantException(Variant(3) < "a");
assertThrown!VariantException("a" < Variant(3));
assertThrown!VariantException(Variant(3) < Variant("a"));
assertThrown!VariantException(Variant.init < Variant(3));
assertThrown!VariantException(Variant(3) < Variant.init);
}
// Handling of unordered types, e.g. issue 9043.
unittest
{
static struct A { int a; }
assert(Variant(A(3)) != A(4));
assertThrown!VariantException(Variant(A(3)) < A(4));
assertThrown!VariantException(A(3) < Variant(A(4)));
assertThrown!VariantException(Variant(A(3)) < Variant(A(4)));
}
/**
* Applies a delegate or function to the given Algebraic depending on the held type,
* ensuring that all types are handled by the visiting functions.
*
* The delegate or function having the currently held value as parameter is called
* with $(D_PARM variant)'s current value. Visiting handlers are passed
* in the template parameter list.
* It is statically ensured that all types of
* $(D_PARAM variant) are handled accross all handlers.
* $(D_PARAM visit) allows delegates and static functions to be passed
* as parameters.
*
* If a function without parameters is specified, this function is called
* when variant doesn't hold a value. Exactly one parameter-less function
* is allowed.
*
* Duplicate overloads matching the same type in one of the visitors are disallowed.
*
* Example:
* -----------------------
* Algebraic!(int, string) variant;
*
* variant = 10;
* assert(variant.visit!((string s) => cast(int)s.length,
* (int i) => i)()
* == 10);
* variant = "string";
* assert(variant.visit!((int i) => return i,
* (string s) => cast(int)s.length)()
* == 6);
*
* // Error function usage
* Algebraic!(int, string) emptyVar;
* assert(variant.visit!((string s) => cast(int)s.length,
* (int i) => i,
* () => -1)()
* == -1);
* ----------------------
* Returns: The return type of visit is deduced from the visiting functions and must be
* the same accross all overloads.
* Throws: If no parameter-less, error function is specified:
* $(D_PARAM VariantException) if $(D_PARAM variant) doesn't hold a value.
*/
template visit(Handler ...)
if (Handler.length > 0)
{
auto visit(VariantType)(VariantType variant)
if (isAlgebraic!VariantType)
{
return visitImpl!(true, VariantType, Handler)(variant);
}
}
unittest
{
Algebraic!(size_t, string) variant;
// not all handled check
static assert(!__traits(compiles, variant.visit!((size_t i){ })() ));
variant = cast(size_t)10;
auto which = 0;
variant.visit!( (string s) => which = 1,
(size_t i) => which = 0
)();
// integer overload was called
assert(which == 0);
// mustn't compile as generic Variant not supported
Variant v;
static assert(!__traits(compiles, v.visit!((string s) => which = 1,
(size_t i) => which = 0
)()
));
static size_t func(string s) {
return s.length;
}
variant = "test";
assert( 4 == variant.visit!(func,
(size_t i) => i
)());
Algebraic!(int, float, string) variant2 = 5.0f;
// Shouldn' t compile as float not handled by visitor.
static assert(!__traits(compiles, variant2.visit!(
(int) {},
(string) {})()));
Algebraic!(size_t, string, float) variant3;
variant3 = 10.0f;
auto floatVisited = false;
assert(variant3.visit!(
(float f) { floatVisited = true; return cast(size_t)f; },
func,
(size_t i) { return i; }
)() == 10);
assert(floatVisited == true);
Algebraic!(float, string) variant4;
assert(variant4.visit!(func, (float f) => cast(size_t)f, () => size_t.max)() == size_t.max);
// double error func check
static assert(!__traits(compiles,
visit!(() => size_t.max, func, (float f) => cast(size_t)f, () => size_t.max)(variant4))
);
}
/**
* Behaves as $(D_PARAM visit) but doesn't enforce that all types are handled
* by the visiting functions.
*
* If a parameter-less function is specified it is called when
* either $(D_PARAM variant) doesn't hold a value or holds a type
* which isn't handled by the visiting functions.
*
* Example:
* -----------------------
* Algebraic!(int, string) variant;
*
* variant = 10;
* auto which = -1;
* variant.tryVisit!((int i) { which = 0; })();
* assert(which = 0);
*
* // Error function usage
* variant = "test";
* variant.tryVisit!((int i) { which = 0; },
* () { which = -100; })();
* assert(which == -100);
* ----------------------
*
* Returns: The return type of tryVisit is deduced from the visiting functions and must be
* the same accross all overloads.
* Throws: If no parameter-less, error function is specified: $(D_PARAM VariantException) if
* $(D_PARAM variant) doesn't hold a value or
* if $(D_PARAM variant) holds a value which isn't handled by the visiting
* functions.
*/
template tryVisit(Handler ...)
if (Handler.length > 0)
{
auto tryVisit(VariantType)(VariantType variant)
if (isAlgebraic!VariantType)
{
return visitImpl!(false, VariantType, Handler)(variant);
}
}
unittest
{
Algebraic!(int, string) variant;
variant = 10;
auto which = -1;
variant.tryVisit!((int i){ which = 0; })();
assert(which == 0);
variant = "test";
assertThrown!VariantException(variant.tryVisit!((int i) { which = 0; })());
void errorfunc()
{
which = -1;
}
variant.tryVisit!((int i) { which = 0; }, errorfunc)();
assert(which == -1);
}
private template isAlgebraic(Type)
{
static if (is(Type _ == VariantN!T, T...))
enum isAlgebraic = T.length >= 2; // T[0] == maxDataSize, T[1..$] == AllowedTypesX
else
enum isAlgebraic = false;
}
unittest
{
static assert(!isAlgebraic!(Variant));
static assert( isAlgebraic!(Algebraic!(string)));
static assert( isAlgebraic!(Algebraic!(int, int[])));
}
private auto visitImpl(bool Strict, VariantType, Handler...)(VariantType variant)
if (isAlgebraic!VariantType && Handler.length > 0)
{
alias VariantType.AllowedTypes AllowedTypes;
/**
* Returns: Struct where $(D_PARAM indices) is an array which
* contains at the n-th position the index in Handler which takes the
* n-th type of AllowedTypes. If an Handler doesn't match an
* AllowedType, -1 is set. If a function in the delegates doesn't
* have parameters, the field $(D_PARAM exceptionFuncIdx) is set;
* otherwise it's -1.
*/
auto visitGetOverloadMap()
{
struct Result {
int[AllowedTypes.length] indices;
int exceptionFuncIdx = -1;
}
Result result;
foreach(tidx, T; AllowedTypes)
{
bool added = false;
foreach(dgidx, dg; Handler)
{
// Handle normal function objects
static if (isSomeFunction!dg)
{
alias ParameterTypeTuple!dg Params;
static if (Params.length == 0)
{
// Just check exception functions in the first
// inner iteration (over delegates)
if (tidx > 0)
continue;
else
{
if (result.exceptionFuncIdx != -1)
assert(false, "duplicate parameter-less (error-)function specified");
result.exceptionFuncIdx = dgidx;
}
}
else if (is(Unqual!(Params[0]) == T))
{
if (added)
assert(false, "duplicate overload specified for type '" ~ T.stringof ~ "'");
added = true;
result.indices[tidx] = dgidx;
}
}
// Handle composite visitors with opCall overloads
else
{
static assert(false, dg.stringof ~ " is not a function or delegate");
}
}
if (!added)
result.indices[tidx] = -1;
}
return result;
}
enum HandlerOverloadMap = visitGetOverloadMap();
if (!variant.hasValue)
{
// Call the exception function. The HandlerOverloadMap
// will have its exceptionFuncIdx field set to value != -1 if an
// exception function has been specified; otherwise we just through an exception.
static if (HandlerOverloadMap.exceptionFuncIdx != -1)
return Handler[ HandlerOverloadMap.exceptionFuncIdx ]();
else
throw new VariantException("variant must hold a value before being visited.");
}
foreach(idx, T; AllowedTypes)
{
if (T* ptr = variant.peek!T())
{
enum dgIdx = HandlerOverloadMap.indices[idx];
static if (dgIdx == -1)
{
static if (Strict)
static assert(false, "overload for type '" ~ T.stringof ~ "' hasn't been specified");
else
{
static if (HandlerOverloadMap.exceptionFuncIdx != -1)
return Handler[ HandlerOverloadMap.exceptionFuncIdx ]();
else
throw new VariantException("variant holds value of type '" ~ T.stringof ~ "' but no visitor has been provided");
}
}
else
{
return Handler[ dgIdx ](*ptr);
}
}
}
assert(false);
}
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