// Written in the D programming language.
/**
Functions that manipulate other functions.
This module provides functions for compile time function composition. These
functions are helpful when constructing predicates for the algorithms in
$(MREF std, algorithm) or $(MREF std, range).
$(SCRIPT inhibitQuickIndex = 1;)
$(DIVC quickindex,
$(BOOKTABLE ,
$(TR $(TH Function Name) $(TH Description)
)
$(TR $(TD $(LREF adjoin))
$(TD Joins a couple of functions into one that executes the original
functions independently and returns a tuple with all the results.
))
$(TR $(TD $(LREF compose), $(LREF pipe))
$(TD Join a couple of functions into one that executes the original
functions one after the other, using one function's result for the next
function's argument.
))
$(TR $(TD $(LREF lessThan), $(LREF greaterThan), $(LREF equalTo))
$(TD Ready-made predicate functions to compare two values.
))
$(TR $(TD $(LREF memoize))
$(TD Creates a function that caches its result for fast re-evaluation.
))
$(TR $(TD $(LREF not))
$(TD Creates a function that negates another.
))
$(TR $(TD $(LREF partial))
$(TD Creates a function that binds the first argument of a given function
to a given value.
))
$(TR $(TD $(LREF curry))
$(TD Converts a multi-argument function into a series of single-argument
functions. f(x, y) == curry(f)(x)(y)
))
$(TR $(TD $(LREF reverseArgs))
$(TD Predicate that reverses the order of its arguments.
))
$(TR $(TD $(LREF toDelegate))
$(TD Converts a callable to a delegate.
))
$(TR $(TD $(LREF unaryFun), $(LREF binaryFun))
$(TD Create a unary or binary function from a string. Most often
used when defining algorithms on ranges.
))
$(TR $(TD $(LREF bind))
$(TD Passes the fields of a struct as arguments to a function.
))
))
Copyright: Copyright Andrei Alexandrescu 2008 - 2009.
License: $(HTTP boost.org/LICENSE_1_0.txt, Boost License 1.0).
Authors: $(HTTP erdani.org, Andrei Alexandrescu)
Source: $(PHOBOSSRC std/functional.d)
*/
/*
Copyright Andrei Alexandrescu 2008 - 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.functional;
import std.meta : AliasSeq, Reverse;
import std.traits : isCallable, Parameters;
import std.conv : toCtString;
import std.internal.attributes : betterC;
public import core.lifetime : forward;
private template needOpCallAlias(alias fun)
{
/* Determine whether or not unaryFun and binaryFun need to alias to fun or
* fun.opCall. Basically, fun is a function object if fun(...) compiles. We
* want is(unaryFun!fun) (resp., is(binaryFun!fun)) to be true if fun is
* any function object. There are 4 possible cases:
*
* 1) fun is the type of a function object with static opCall;
* 2) fun is an instance of a function object with static opCall;
* 3) fun is the type of a function object with non-static opCall;
* 4) fun is an instance of a function object with non-static opCall.
*
* In case (1), is(unaryFun!fun) should compile, but does not if unaryFun
* aliases itself to fun, because typeof(fun) is an error when fun itself
* is a type. So it must be aliased to fun.opCall instead. All other cases
* should be aliased to fun directly.
*/
static if (is(typeof(fun.opCall) == function))
{
enum needOpCallAlias = !is(typeof(fun)) && __traits(compiles, () {
return fun(Parameters!fun.init);
});
}
else
enum needOpCallAlias = false;
}
/**
Transforms a `string` representing an expression into a unary
function. The `string` must either use symbol name `a` as
the parameter or provide the symbol via the `parmName` argument.
Params:
fun = a `string` or a callable
parmName = the name of the parameter if `fun` is a string. Defaults
to `"a"`.
Returns:
If `fun` is a `string`, a new single parameter function
If `fun` is not a `string`, an alias to `fun`.
*/
template unaryFun(alias fun, string parmName = "a")
{
static if (is(typeof(fun) : string))
{
static if (!fun._ctfeMatchUnary(parmName))
{
import std.algorithm, std.conv, std.exception, std.math, std.range, std.string;
import std.meta, std.traits, std.typecons;
}
auto unaryFun(ElementType)(auto ref ElementType __a)
{
mixin("alias " ~ parmName ~ " = __a ;");
return mixin(fun);
}
}
else static if (needOpCallAlias!fun)
{
// https://issues.dlang.org/show_bug.cgi?id=9906
alias unaryFun = fun.opCall;
}
else
{
alias unaryFun = fun;
}
}
///
@safe unittest
{
// Strings are compiled into functions:
alias isEven = unaryFun!("(a & 1) == 0");
assert(isEven(2) && !isEven(1));
}
@safe unittest
{
static int f1(int a) { return a + 1; }
static assert(is(typeof(unaryFun!(f1)(1)) == int));
assert(unaryFun!(f1)(41) == 42);
int f2(int a) { return a + 1; }
static assert(is(typeof(unaryFun!(f2)(1)) == int));
assert(unaryFun!(f2)(41) == 42);
assert(unaryFun!("a + 1")(41) == 42);
//assert(unaryFun!("return a + 1;")(41) == 42);
int num = 41;
assert(unaryFun!"a + 1"(num) == 42);
// https://issues.dlang.org/show_bug.cgi?id=9906
struct Seen
{
static bool opCall(int n) { return true; }
}
static assert(needOpCallAlias!Seen);
static assert(is(typeof(unaryFun!Seen(1))));
assert(unaryFun!Seen(1));
Seen s;
static assert(!needOpCallAlias!s);
static assert(is(typeof(unaryFun!s(1))));
assert(unaryFun!s(1));
struct FuncObj
{
bool opCall(int n) { return true; }
}
FuncObj fo;
static assert(!needOpCallAlias!fo);
static assert(is(typeof(unaryFun!fo)));
assert(unaryFun!fo(1));
// Function object with non-static opCall can only be called with an
// instance, not with merely the type.
static assert(!is(typeof(unaryFun!FuncObj)));
}
/**
Transforms a `string` representing an expression into a binary function. The
`string` must either use symbol names `a` and `b` as the parameters or
provide the symbols via the `parm1Name` and `parm2Name` arguments.
Params:
fun = a `string` or a callable
parm1Name = the name of the first parameter if `fun` is a string.
Defaults to `"a"`.
parm2Name = the name of the second parameter if `fun` is a string.
Defaults to `"b"`.
Returns:
If `fun` is not a string, `binaryFun` aliases itself away to
`fun`.
*/
template binaryFun(alias fun, string parm1Name = "a",
string parm2Name = "b")
{
static if (is(typeof(fun) : string))
{
static if (!fun._ctfeMatchBinary(parm1Name, parm2Name))
{
import std.algorithm, std.conv, std.exception, std.math, std.range, std.string;
import std.meta, std.traits, std.typecons;
}
auto binaryFun(ElementType1, ElementType2)
(auto ref ElementType1 __a, auto ref ElementType2 __b)
{
mixin("alias "~parm1Name~" = __a ;");
mixin("alias "~parm2Name~" = __b ;");
return mixin(fun);
}
}
else static if (needOpCallAlias!fun)
{
// https://issues.dlang.org/show_bug.cgi?id=9906
alias binaryFun = fun.opCall;
}
else
{
alias binaryFun = fun;
}
}
///
@safe unittest
{
alias less = binaryFun!("a < b");
assert(less(1, 2) && !less(2, 1));
alias greater = binaryFun!("a > b");
assert(!greater("1", "2") && greater("2", "1"));
}
@safe unittest
{
static int f1(int a, string b) { return a + 1; }
static assert(is(typeof(binaryFun!(f1)(1, "2")) == int));
assert(binaryFun!(f1)(41, "a") == 42);
string f2(int a, string b) { return b ~ "2"; }
static assert(is(typeof(binaryFun!(f2)(1, "1")) == string));
assert(binaryFun!(f2)(1, "4") == "42");
assert(binaryFun!("a + b")(41, 1) == 42);
//@@BUG
//assert(binaryFun!("return a + b;")(41, 1) == 42);
// https://issues.dlang.org/show_bug.cgi?id=9906
struct Seen
{
static bool opCall(int x, int y) { return true; }
}
static assert(is(typeof(binaryFun!Seen)));
assert(binaryFun!Seen(1,1));
struct FuncObj
{
bool opCall(int x, int y) { return true; }
}
FuncObj fo;
static assert(!needOpCallAlias!fo);
static assert(is(typeof(binaryFun!fo)));
assert(unaryFun!fo(1,1));
// Function object with non-static opCall can only be called with an
// instance, not with merely the type.
static assert(!is(typeof(binaryFun!FuncObj)));
}
// skip all ASCII chars except a .. z, A .. Z, 0 .. 9, '_' and '.'.
private uint _ctfeSkipOp(ref string op)
{
if (!__ctfe) assert(false);
import std.ascii : isASCII, isAlphaNum;
immutable oldLength = op.length;
while (op.length)
{
immutable front = op[0];
if (front.isASCII() && !(front.isAlphaNum() || front == '_' || front == '.'))
op = op[1..$];
else
break;
}
return oldLength != op.length;
}
// skip all digits
private uint _ctfeSkipInteger(ref string op)
{
if (!__ctfe) assert(false);
import std.ascii : isDigit;
immutable oldLength = op.length;
while (op.length)
{
immutable front = op[0];
if (front.isDigit())
op = op[1..$];
else
break;
}
return oldLength != op.length;
}
// skip name
private uint _ctfeSkipName(ref string op, string name)
{
if (!__ctfe) assert(false);
if (op.length >= name.length && op[0 .. name.length] == name)
{
op = op[name.length..$];
return 1;
}
return 0;
}
// returns 1 if `fun` is trivial unary function
private uint _ctfeMatchUnary(string fun, string name)
{
if (!__ctfe) assert(false);
fun._ctfeSkipOp();
for (;;)
{
immutable h = fun._ctfeSkipName(name) + fun._ctfeSkipInteger();
if (h == 0)
{
fun._ctfeSkipOp();
break;
}
else if (h == 1)
{
if (!fun._ctfeSkipOp())
break;
}
else
return 0;
}
return fun.length == 0;
}
@safe unittest
{
static assert(!_ctfeMatchUnary("sqrt(ё)", "ё"));
static assert(!_ctfeMatchUnary("ё.sqrt", "ё"));
static assert(!_ctfeMatchUnary(".ё+ё", "ё"));
static assert(!_ctfeMatchUnary("_ё+ё", "ё"));
static assert(!_ctfeMatchUnary("ёё", "ё"));
static assert(_ctfeMatchUnary("a+a", "a"));
static assert(_ctfeMatchUnary("a + 10", "a"));
static assert(_ctfeMatchUnary("4 == a", "a"));
static assert(_ctfeMatchUnary("2 == a", "a"));
static assert(_ctfeMatchUnary("1 != a", "a"));
static assert(_ctfeMatchUnary("a != 4", "a"));
static assert(_ctfeMatchUnary("a< 1", "a"));
static assert(_ctfeMatchUnary("434 < a", "a"));
static assert(_ctfeMatchUnary("132 > a", "a"));
static assert(_ctfeMatchUnary("123 >a", "a"));
static assert(_ctfeMatchUnary("a>82", "a"));
static assert(_ctfeMatchUnary("ё>82", "ё"));
static assert(_ctfeMatchUnary("ё[ё(ё)]", "ё"));
static assert(_ctfeMatchUnary("ё[21]", "ё"));
}
// returns 1 if `fun` is trivial binary function
private uint _ctfeMatchBinary(string fun, string name1, string name2)
{
if (!__ctfe) assert(false);
fun._ctfeSkipOp();
for (;;)
{
immutable h = fun._ctfeSkipName(name1) + fun._ctfeSkipName(name2) + fun._ctfeSkipInteger();
if (h == 0)
{
fun._ctfeSkipOp();
break;
}
else if (h == 1)
{
if (!fun._ctfeSkipOp())
break;
}
else
return 0;
}
return fun.length == 0;
}
@safe unittest
{
static assert(!_ctfeMatchBinary("sqrt(ё)", "ё", "b"));
static assert(!_ctfeMatchBinary("ё.sqrt", "ё", "b"));
static assert(!_ctfeMatchBinary(".ё+ё", "ё", "b"));
static assert(!_ctfeMatchBinary("_ё+ё", "ё", "b"));
static assert(!_ctfeMatchBinary("ёё", "ё", "b"));
static assert(_ctfeMatchBinary("a+a", "a", "b"));
static assert(_ctfeMatchBinary("a + 10", "a", "b"));
static assert(_ctfeMatchBinary("4 == a", "a", "b"));
static assert(_ctfeMatchBinary("2 == a", "a", "b"));
static assert(_ctfeMatchBinary("1 != a", "a", "b"));
static assert(_ctfeMatchBinary("a != 4", "a", "b"));
static assert(_ctfeMatchBinary("a< 1", "a", "b"));
static assert(_ctfeMatchBinary("434 < a", "a", "b"));
static assert(_ctfeMatchBinary("132 > a", "a", "b"));
static assert(_ctfeMatchBinary("123 >a", "a", "b"));
static assert(_ctfeMatchBinary("a>82", "a", "b"));
static assert(_ctfeMatchBinary("ё>82", "ё", "q"));
static assert(_ctfeMatchBinary("ё[ё(10)]", "ё", "q"));
static assert(_ctfeMatchBinary("ё[21]", "ё", "q"));
static assert(!_ctfeMatchBinary("sqrt(ё)+b", "b", "ё"));
static assert(!_ctfeMatchBinary("ё.sqrt-b", "b", "ё"));
static assert(!_ctfeMatchBinary(".ё+b", "b", "ё"));
static assert(!_ctfeMatchBinary("_b+ё", "b", "ё"));
static assert(!_ctfeMatchBinary("ba", "b", "a"));
static assert(_ctfeMatchBinary("a+b", "b", "a"));
static assert(_ctfeMatchBinary("a + b", "b", "a"));
static assert(_ctfeMatchBinary("b == a", "b", "a"));
static assert(_ctfeMatchBinary("b == a", "b", "a"));
static assert(_ctfeMatchBinary("b != a", "b", "a"));
static assert(_ctfeMatchBinary("a != b", "b", "a"));
static assert(_ctfeMatchBinary("a< b", "b", "a"));
static assert(_ctfeMatchBinary("b < a", "b", "a"));
static assert(_ctfeMatchBinary("b > a", "b", "a"));
static assert(_ctfeMatchBinary("b >a", "b", "a"));
static assert(_ctfeMatchBinary("a>b", "b", "a"));
static assert(_ctfeMatchBinary("ё>b", "b", "ё"));
static assert(_ctfeMatchBinary("b[ё(-1)]", "b", "ё"));
static assert(_ctfeMatchBinary("ё[-21]", "b", "ё"));
}
//undocumented
template safeOp(string S)
if (S=="<"||S==">"||S=="<="||S==">="||S=="=="||S=="!=")
{
import std.traits : isIntegral;
private bool unsafeOp(ElementType1, ElementType2)(ElementType1 a, ElementType2 b) pure
if (isIntegral!ElementType1 && isIntegral!ElementType2)
{
import std.traits : CommonType;
alias T = CommonType!(ElementType1, ElementType2);
return mixin("cast(T)a "~S~" cast(T) b");
}
bool safeOp(T0, T1)(auto ref T0 a, auto ref T1 b)
{
import std.traits : mostNegative;
static if (isIntegral!T0 && isIntegral!T1 &&
(mostNegative!T0 < 0) != (mostNegative!T1 < 0))
{
static if (S == "<=" || S == "<")
{
static if (mostNegative!T0 < 0)
immutable result = a < 0 || unsafeOp(a, b);
else
immutable result = b >= 0 && unsafeOp(a, b);
}
else
{
static if (mostNegative!T0 < 0)
immutable result = a >= 0 && unsafeOp(a, b);
else
immutable result = b < 0 || unsafeOp(a, b);
}
}
else
{
static assert(is(typeof(mixin("a "~S~" b"))),
"Invalid arguments: Cannot compare types " ~ T0.stringof ~ " and " ~ T1.stringof ~ ".");
immutable result = mixin("a "~S~" b");
}
return result;
}
}
@safe unittest //check user defined types
{
import std.algorithm.comparison : equal;
struct Foo
{
int a;
auto opEquals(Foo foo)
{
return a == foo.a;
}
}
assert(safeOp!"!="(Foo(1), Foo(2)));
}
/**
Predicate that returns $(D_PARAM a < b).
Correctly compares signed and unsigned integers, ie. -1 < 2U.
*/
alias lessThan = safeOp!"<";
///
pure @safe @nogc nothrow unittest
{
assert(lessThan(2, 3));
assert(lessThan(2U, 3U));
assert(lessThan(2, 3.0));
assert(lessThan(-2, 3U));
assert(lessThan(2, 3U));
assert(!lessThan(3U, -2));
assert(!lessThan(3U, 2));
assert(!lessThan(0, 0));
assert(!lessThan(0U, 0));
assert(!lessThan(0, 0U));
}
/**
Predicate that returns $(D_PARAM a > b).
Correctly compares signed and unsigned integers, ie. 2U > -1.
*/
alias greaterThan = safeOp!">";
///
@safe unittest
{
assert(!greaterThan(2, 3));
assert(!greaterThan(2U, 3U));
assert(!greaterThan(2, 3.0));
assert(!greaterThan(-2, 3U));
assert(!greaterThan(2, 3U));
assert(greaterThan(3U, -2));
assert(greaterThan(3U, 2));
assert(!greaterThan(0, 0));
assert(!greaterThan(0U, 0));
assert(!greaterThan(0, 0U));
}
/**
Predicate that returns $(D_PARAM a == b).
Correctly compares signed and unsigned integers, ie. !(-1 == ~0U).
*/
alias equalTo = safeOp!"==";
///
@safe unittest
{
assert(equalTo(0U, 0));
assert(equalTo(0, 0U));
assert(!equalTo(-1, ~0U));
}
/**
N-ary predicate that reverses the order of arguments, e.g., given
$(D pred(a, b, c)), returns $(D pred(c, b, a)).
Params:
pred = A callable
Returns:
A function which calls `pred` after reversing the given parameters
*/
template reverseArgs(alias pred)
{
auto reverseArgs(Args...)(auto ref Args args)
if (is(typeof(pred(Reverse!args))))
{
return pred(Reverse!args);
}
}
///
@safe unittest
{
alias gt = reverseArgs!(binaryFun!("a < b"));
assert(gt(2, 1) && !gt(1, 1));
}
///
@safe unittest
{
int x = 42;
bool xyz(int a, int b) { return a * x < b / x; }
auto foo = &xyz;
foo(4, 5);
alias zyx = reverseArgs!(foo);
assert(zyx(5, 4) == foo(4, 5));
}
///
@safe unittest
{
alias gt = reverseArgs!(binaryFun!("a < b"));
assert(gt(2, 1) && !gt(1, 1));
int x = 42;
bool xyz(int a, int b) { return a * x < b / x; }
auto foo = &xyz;
foo(4, 5);
alias zyx = reverseArgs!(foo);
assert(zyx(5, 4) == foo(4, 5));
}
///
@safe unittest
{
int abc(int a, int b, int c) { return a * b + c; }
alias cba = reverseArgs!abc;
assert(abc(91, 17, 32) == cba(32, 17, 91));
}
///
@safe unittest
{
int a(int a) { return a * 2; }
alias _a = reverseArgs!a;
assert(a(2) == _a(2));
}
///
@safe unittest
{
int b() { return 4; }
alias _b = reverseArgs!b;
assert(b() == _b());
}
/**
Negates predicate `pred`.
Params:
pred = A string or a callable
Returns:
A function which calls `pred` and returns the logical negation of its
return value.
*/
template not(alias pred)
{
auto not(T...)(auto ref T args)
{
static if (is(typeof(!pred(args))))
return !pred(args);
else static if (T.length == 1)
return !unaryFun!pred(args);
else static if (T.length == 2)
return !binaryFun!pred(args);
else
static assert(0);
}
}
///
@safe unittest
{
import std.algorithm.searching : find;
import std.uni : isWhite;
string a = " Hello, world!";
assert(find!(not!isWhite)(a) == "Hello, world!");
}
@safe unittest
{
assert(not!"a != 5"(5));
assert(not!"a != b"(5, 5));
assert(not!(() => false)());
assert(not!(a => a != 5)(5));
assert(not!((a, b) => a != b)(5, 5));
assert(not!((a, b, c) => a * b * c != 125 )(5, 5, 5));
}
/**
$(LINK2 http://en.wikipedia.org/wiki/Partial_application, Partially
applies) $(D_PARAM fun) by tying its first argument to $(D_PARAM arg).
Params:
fun = A callable
arg = The first argument to apply to `fun`
Returns:
A new function which calls `fun` with `arg` plus the passed parameters.
*/
template partial(alias fun, alias arg)
{
import std.traits : isCallable;
// Check whether fun is a user defined type which implements opCall or a template.
// As opCall itself can be templated, std.traits.isCallable does not work here.
enum isSomeFunctor = (is(typeof(fun) == struct) || is(typeof(fun) == class)) && __traits(hasMember, fun, "opCall");
static if (isSomeFunctor || __traits(isTemplate, fun))
{
auto partial(Ts...)(Ts args2)
{
static if (is(typeof(fun(arg, args2))))
{
return fun(arg, args2);
}
else
{
static string errormsg()
{
string msg = "Cannot call '" ~ fun.stringof ~ "' with arguments " ~
"(" ~ arg.stringof;
foreach (T; Ts)
msg ~= ", " ~ T.stringof;
msg ~= ").";
return msg;
}
static assert(0, errormsg());
}
}
}
else static if (!isCallable!fun)
{
static assert(false, "Cannot apply partial to a non-callable '" ~ fun.stringof ~ "'.");
}
else
{
import std.meta : Filter;
static if (__traits(compiles, __traits(getOverloads,
__traits(parent, fun), __traits(identifier, fun))))
alias overloads = __traits(getOverloads, __traits(parent, fun),
__traits(identifier, fun));
else
alias overloads = AliasSeq!(fun);
enum isCallableWithArg(alias fun) = Parameters!fun.length > 0 &&
is(typeof(arg) : Parameters!fun[0]);
alias candidates = Filter!(isCallableWithArg, overloads);
static if (overloads.length == 1 && Parameters!fun.length == 0)
{
static assert(0, "Cannot partially apply '" ~ fun.stringof ~ "'." ~
"'" ~ fun.stringof ~ "' has 0 arguments.");
}
else static if (candidates.length == 0)
{
import std.meta : NoDuplicates, staticMap;
enum hasParameters(alias fun) = Parameters!fun.length > 0;
alias firstParameter(alias fun) = Parameters!fun[0];
alias firstParameters = NoDuplicates!(
staticMap!(firstParameter, Filter!(hasParameters, overloads)));
string errorMsg()
{
string msg = "Argument mismatch for '" ~ fun.stringof ~
"': expected " ~ firstParameters[0].stringof;
static foreach (firstParam; firstParameters[1 .. $])
msg ~= " or " ~ firstParam.stringof;
msg ~= ", but got " ~ typeof(arg).stringof ~ ".";
return msg;
}
static assert(0, errorMsg());
}
else
{
import std.traits : ReturnType;
static foreach (candidate; candidates)
ReturnType!candidate partial(Parameters!candidate[1..$] args2)
{
return candidate(arg, args2);
}
}
}
}
///
@safe unittest
{
int fun(int a, int b) { return a + b; }
alias fun5 = partial!(fun, 5);
assert(fun5(6) == 11);
// Note that in most cases you'd use an alias instead of a value
// assignment. Using an alias allows you to partially evaluate template
// functions without committing to a particular type of the function.
}
// https://issues.dlang.org/show_bug.cgi?id=21457
///
@safe unittest
{
// Overloads are resolved when the partially applied function is called
// with the remaining arguments.
struct S
{
static char fun(int i, string s) { return s[i]; }
static int fun(int a, int b) { return a * b; }
}
alias fun3 = partial!(S.fun, 3);
assert(fun3("hello") == 'l');
assert(fun3(10) == 30);
}
// tests for partially evaluating callables
@safe unittest
{
static int f1(int a, int b) { return a + b; }
assert(partial!(f1, 5)(6) == 11);
int f2(int a, int b) { return a + b; }
int x = 5;
assert(partial!(f2, x)(6) == 11);
x = 7;
assert(partial!(f2, x)(6) == 13);
static assert(partial!(f2, 5)(6) == 11);
auto dg = &f2;
auto f3 = &partial!(dg, x);
assert(f3(6) == 13);
static int funOneArg(int a) { return a; }
assert(partial!(funOneArg, 1)() == 1);
static int funThreeArgs(int a, int b, int c) { return a + b + c; }
alias funThreeArgs1 = partial!(funThreeArgs, 1);
assert(funThreeArgs1(2, 3) == 6);
static assert(!is(typeof(funThreeArgs1(2))));
enum xe = 5;
alias fe = partial!(f2, xe);
static assert(fe(6) == 11);
}
// tests for partially evaluating templated/overloaded callables
@safe unittest
{
static auto add(A, B)(A x, B y)
{
return x + y;
}
alias add5 = partial!(add, 5);
assert(add5(6) == 11);
static assert(!is(typeof(add5())));
static assert(!is(typeof(add5(6, 7))));
// taking address of templated partial evaluation needs explicit type
auto dg = &add5!(int);
assert(dg(6) == 11);
int x = 5;
alias addX = partial!(add, x);
assert(addX(6) == 11);
static struct Callable
{
static string opCall(string a, string b) { return a ~ b; }
int opCall(int a, int b) { return a * b; }
double opCall(double a, double b) { return a + b; }
}
Callable callable;
assert(partial!(Callable, "5")("6") == "56");
assert(partial!(callable, 5)(6) == 30);
assert(partial!(callable, 7.0)(3.0) == 7.0 + 3.0);
static struct TCallable
{
auto opCall(A, B)(A a, B b)
{
return a + b;
}
}
TCallable tcallable;
assert(partial!(tcallable, 5)(6) == 11);
static assert(!is(typeof(partial!(tcallable, "5")(6))));
static struct NonCallable{}
static assert(!__traits(compiles, partial!(NonCallable, 5)), "Partial should not work on non-callable structs.");
static assert(!__traits(compiles, partial!(NonCallable.init, 5)),
"Partial should not work on instances of non-callable structs.");
static A funOneArg(A)(A a) { return a; }
alias funOneArg1 = partial!(funOneArg, 1);
assert(funOneArg1() == 1);
static auto funThreeArgs(A, B, C)(A a, B b, C c) { return a + b + c; }
alias funThreeArgs1 = partial!(funThreeArgs, 1);
assert(funThreeArgs1(2, 3) == 6);
static assert(!is(typeof(funThreeArgs1(1))));
auto dg2 = &funOneArg1!();
assert(dg2() == 1);
}
// Fix https://issues.dlang.org/show_bug.cgi?id=15732
@safe unittest
{
// Test whether it works with functions.
auto partialFunction(){
auto fullFunction = (float a, float b, float c) => a + b / c;
alias apply1 = partial!(fullFunction, 1);
return &apply1;
}
auto result = partialFunction()(2, 4);
assert(result == 1.5f);
// And with delegates.
auto partialDelegate(float c){
auto fullDelegate = (float a, float b) => a + b / c;
alias apply1 = partial!(fullDelegate, 1);
return &apply1;
}
auto result2 = partialDelegate(4)(2);
assert(result2 == 1.5f);
}
/**
Takes a function of (potentially) many arguments, and returns a function taking
one argument and returns a callable taking the rest. f(x, y) == curry(f)(x)(y)
Params:
F = a function taking at least one argument
t = a callable object whose opCall takes at least 1 object
Returns:
A single parameter callable object
*/
template curry(alias F)
if (isCallable!F && Parameters!F.length)
{
//inspired from the implementation from Artur Skawina here:
//https://forum.dlang.org/post/mailman.1626.1340110492.24740.digitalmars-d@puremagic.com
//This implementation stores a copy of all filled in arguments with each curried result
//this way, the curried functions are independent and don't share any references
//eg: auto fc = curry!f; auto fc1 = fc(1); auto fc2 = fc(2); fc1(3) != fc2(3)
struct CurryImpl(size_t N)
{
alias FParams = Parameters!F;
FParams[0 .. N] storedArguments;
static if (N > 0)
{
this(U : FParams[N - 1])(ref CurryImpl!(N - 1) prev, ref U arg)
{
storedArguments[0 .. N - 1] = prev.storedArguments[];
storedArguments[N-1] = arg;
}
}
auto opCall(U : FParams[N])(auto ref U arg) return scope
{
static if (N == FParams.length - 1)
{
return F(storedArguments, arg);
}
else
{
return CurryImpl!(N + 1)(this, arg);
}
}
}
auto curry()
{
CurryImpl!0 res;
return res; // return CurryImpl!0.init segfaults for delegates on Windows
}
}
///
pure @safe @nogc nothrow unittest
{
int f(int x, int y, int z)
{
return x + y + z;
}
auto cf = curry!f;
auto cf1 = cf(1);
auto cf2 = cf(2);
assert(cf1(2)(3) == f(1, 2, 3));
assert(cf2(2)(3) == f(2, 2, 3));
}
///ditto
auto curry(T)(T t)
if (isCallable!T && Parameters!T.length)
{
static auto fun(ref T inst, ref Parameters!T args)
{
return inst(args);
}
return curry!fun()(t);
}
///
pure @safe @nogc nothrow unittest
{
//works with callable structs too
struct S
{
int w;
int opCall(int x, int y, int z)
{
return w + x + y + z;
}
}
S s;
s.w = 5;
auto cs = curry(s);
auto cs1 = cs(1);
auto cs2 = cs(2);
assert(cs1(2)(3) == s(1, 2, 3));
assert(cs1(2)(3) == (1 + 2 + 3 + 5));
assert(cs2(2)(3) ==s(2, 2, 3));
}
@safe pure @nogc nothrow unittest
{
//currying a single argument function does nothing
int pork(int a){ return a*2;}
auto curryPork = curry!pork;
assert(curryPork(0) == pork(0));
assert(curryPork(1) == pork(1));
assert(curryPork(-1) == pork(-1));
assert(curryPork(1000) == pork(1000));
//test 2 argument function
double mixedVeggies(double a, int b, bool)
{
return a + b;
}
auto mixedCurry = curry!mixedVeggies;
assert(mixedCurry(10)(20)(false) == mixedVeggies(10, 20, false));
assert(mixedCurry(100)(200)(true) == mixedVeggies(100, 200, true));
// struct with opCall
struct S
{
double opCall(int x, double y, short z) const pure nothrow @nogc
{
return x*y*z;
}
}
S s;
auto curriedStruct = curry(s);
assert(curriedStruct(1)(2)(short(3)) == s(1, 2, short(3)));
assert(curriedStruct(300)(20)(short(10)) == s(300, 20, short(10)));
}
pure @safe nothrow unittest
{
auto cfl = curry!((double a, int b) => a + b);
assert(cfl(13)(2) == 15);
int c = 42;
auto cdg = curry!((double a, int b) => a + b + c);
assert(cdg(13)(2) == 57);
static class C
{
int opCall(int mult, int add) pure @safe nothrow @nogc scope
{
return mult * 42 + add;
}
}
scope C ci = new C();
scope cc = curry(ci);
assert(cc(2)(4) == ci(2, 4));
}
// Disallows callables without parameters
pure @safe @nogc nothrow unittest
{
static void noargs() {}
static assert(!__traits(compiles, curry!noargs()));
static struct NoArgs
{
void opCall() {}
}
static assert(!__traits(compiles, curry(NoArgs.init)));
}
private template Iota(size_t n)
{
static if (n == 0)
alias Iota = AliasSeq!();
else
alias Iota = AliasSeq!(Iota!(n - 1), n - 1);
}
/**
Takes multiple functions and adjoins them together.
Params:
F = the call-able(s) to adjoin
Returns:
A new function which returns a $(REF Tuple, std,typecons). Each of the
elements of the tuple will be the return values of `F`.
Note: In the special case where only a single function is provided
($(D F.length == 1)), adjoin simply aliases to the single passed function
(`F[0]`).
*/
template adjoin(F...)
if (F.length >= 1)
{
static if (F.length == 1)
alias adjoin = F[0];
else
auto adjoin(V...)(auto ref V a)
{
import std.typecons : tuple;
import std.meta : staticMap;
auto resultElement(size_t i)()
{
return F[i](a);
}
return tuple(staticMap!(resultElement, Iota!(F.length)));
}
}
///
@safe unittest
{
import std.typecons : Tuple;
static bool f1(int a) { return a != 0; }
static int f2(int a) { return a / 2; }
auto x = adjoin!(f1, f2)(5);
assert(is(typeof(x) == Tuple!(bool, int)));
assert(x[0] == true && x[1] == 2);
}
@safe unittest
{
import std.typecons : Tuple;
static bool F1(int a) { return a != 0; }
auto x1 = adjoin!(F1)(5);
static int F2(int a) { return a / 2; }
auto x2 = adjoin!(F1, F2)(5);
assert(is(typeof(x2) == Tuple!(bool, int)));
assert(x2[0] && x2[1] == 2);
auto x3 = adjoin!(F1, F2, F2)(5);
assert(is(typeof(x3) == Tuple!(bool, int, int)));
assert(x3[0] && x3[1] == 2 && x3[2] == 2);
bool F4(int a) { return a != x1; }
alias eff4 = adjoin!(F4);
static struct S
{
bool delegate(int) @safe store;
int fun() { return 42 + store(5); }
}
S s;
s.store = (int a) { return eff4(a); };
auto x4 = s.fun();
assert(x4 == 43);
}
@safe unittest
{
import std.meta : staticMap;
import std.typecons : Tuple, tuple;
alias funs = staticMap!(unaryFun, "a", "a * 2", "a * 3", "a * a", "-a");
alias afun = adjoin!funs;
assert(afun(5) == tuple(5, 10, 15, 25, -5));
static class C{}
alias IC = immutable(C);
IC foo(){return typeof(return).init;}
Tuple!(IC, IC, IC, IC) ret1 = adjoin!(foo, foo, foo, foo)();
static struct S{int* p;}
alias IS = immutable(S);
IS bar(){return typeof(return).init;}
enum Tuple!(IS, IS, IS, IS) ret2 = adjoin!(bar, bar, bar, bar)();
}
// https://issues.dlang.org/show_bug.cgi?id=21347
@safe @betterC unittest
{
alias f = (int n) => n + 1;
alias g = (int n) => n + 2;
alias h = (int n) => n + 3;
alias i = (int n) => n + 4;
auto result = adjoin!(f, g, h, i)(0);
assert(result[0] == 1);
assert(result[1] == 2);
assert(result[2] == 3);
assert(result[3] == 4);
}
/**
Composes passed-in functions $(D fun[0], fun[1], ...).
Params:
fun = the call-able(s) or `string`(s) to compose into one function
Returns:
A new function `f(x)` that in turn returns `fun[0](fun[1](...(x)))...`.
See_Also: $(LREF pipe)
*/
template compose(fun...)
if (fun.length > 0)
{
static if (fun.length == 1)
{
alias compose = unaryFun!(fun[0]);
}
else
{
alias fun0 = unaryFun!(fun[0]);
alias rest = compose!(fun[1 .. $]);
auto compose(Args...)(Args args)
{
return fun0(rest(args));
}
}
}
///
@safe unittest
{
import std.algorithm.comparison : equal;
import std.algorithm.iteration : map;
import std.array : split;
import std.conv : to;
// First split a string in whitespace-separated tokens and then
// convert each token into an integer
assert(compose!(map!(to!(int)), split)("1 2 3").equal([1, 2, 3]));
}
// https://issues.dlang.org/show_bug.cgi?id=6484
@safe unittest
{
int f(int a) { return a; }
int g(int a) { return a; }
int h(int a,int b,int c) { return a * b * c; }
alias F = compose!(f,g,h);
assert(F(1,2,3) == f(g(h(1,2,3))));
}
/**
Pipes functions in sequence. Offers the same functionality as $(D
compose), but with functions specified in reverse order. This may
lead to more readable code in some situation because the order of
execution is the same as lexical order.
Params:
fun = the call-able(s) or `string`(s) to compose into one function
Returns:
A new function `f(x)` that in turn returns `fun[$-1](...fun[1](fun[0](x)))...`.
Example:
----
// Read an entire text file, split the resulting string in
// whitespace-separated tokens, and then convert each token into an
// integer
int[] a = pipe!(readText, split, map!(to!(int)))("file.txt");
----
See_Also: $(LREF compose)
*/
alias pipe(fun...) = compose!(Reverse!(fun));
///
@safe unittest
{
import std.conv : to;
string foo(int a) { return to!(string)(a); }
int bar(string a) { return to!(int)(a) + 1; }
double baz(int a) { return a + 0.5; }
assert(compose!(baz, bar, foo)(1) == 2.5);
assert(pipe!(foo, bar, baz)(1) == 2.5);
assert(compose!(baz, `to!(int)(a) + 1`, foo)(1) == 2.5);
assert(compose!(baz, bar)("1"[]) == 2.5);
assert(compose!(baz, bar)("1") == 2.5);
assert(compose!(`a + 0.5`, `to!(int)(a) + 1`, foo)(1) == 2.5);
}
/**
* $(LINK2 https://en.wikipedia.org/wiki/Memoization, Memoizes) a function so as
* to avoid repeated computation. The memoization structure is a hash table keyed by a
* tuple of the function's arguments. There is a speed gain if the
* function is repeatedly called with the same arguments and is more
* expensive than a hash table lookup. For more information on memoization, refer to $(HTTP docs.google.com/viewer?url=http%3A%2F%2Fhop.perl.plover.com%2Fbook%2Fpdf%2F03CachingAndMemoization.pdf, this book chapter).
Example:
----
double transmogrify(int a, string b)
{
... expensive computation ...
}
alias fastTransmogrify = memoize!transmogrify;
unittest
{
auto slow = transmogrify(2, "hello");
auto fast = fastTransmogrify(2, "hello");
assert(slow == fast);
}
----
Params:
fun = the call-able to memozie
maxSize = The maximum size of the GC buffer to hold the return values
Returns:
A new function which calls `fun` and caches its return values.
Note:
Technically the memoized function should be pure because `memoize` assumes it will
always return the same result for a given tuple of arguments. However, `memoize` does not
enforce that because sometimes it is useful to memoize an impure function, too.
*/
template memoize(alias fun)
{
import std.traits : ReturnType;
// https://issues.dlang.org/show_bug.cgi?id=13580
// alias Args = Parameters!fun;
ReturnType!fun memoize(Parameters!fun args)
{
alias Args = Parameters!fun;
import std.typecons : Tuple;
import std.traits : Unqual;
static Unqual!(ReturnType!fun)[Tuple!Args] memo;
auto t = Tuple!Args(args);
if (auto p = t in memo)
return *p;
auto r = fun(args);
memo[t] = r;
return r;
}
}
/// ditto
template memoize(alias fun, uint maxSize)
{
import std.traits : ReturnType;
// https://issues.dlang.org/show_bug.cgi?id=13580
// alias Args = Parameters!fun;
ReturnType!fun memoize(Parameters!fun args)
{
import std.meta : staticMap;
import std.traits : hasIndirections, Unqual;
import std.typecons : tuple;
static struct Value { staticMap!(Unqual, Parameters!fun) args; Unqual!(ReturnType!fun) res; }
static Value[] memo;
static size_t[] initialized;
if (!memo.length)
{
import core.memory : GC;
// Ensure no allocation overflows
static assert(maxSize < size_t.max / Value.sizeof);
static assert(maxSize < size_t.max - (8 * size_t.sizeof - 1));
enum attr = GC.BlkAttr.NO_INTERIOR | (hasIndirections!Value ? 0 : GC.BlkAttr.NO_SCAN);
memo = (cast(Value*) GC.malloc(Value.sizeof * maxSize, attr))[0 .. maxSize];
enum nwords = (maxSize + 8 * size_t.sizeof - 1) / (8 * size_t.sizeof);
initialized = (cast(size_t*) GC.calloc(nwords * size_t.sizeof, attr | GC.BlkAttr.NO_SCAN))[0 .. nwords];
}
import core.bitop : bt, bts;
import core.lifetime : emplace;
size_t hash;
foreach (ref arg; args)
hash = hashOf(arg, hash);
// cuckoo hashing
immutable idx1 = hash % maxSize;
if (!bt(initialized.ptr, idx1))
{
emplace(&memo[idx1], args, fun(args));
// only set to initialized after setting args and value
// https://issues.dlang.org/show_bug.cgi?id=14025
bts(initialized.ptr, idx1);
return memo[idx1].res;
}
else if (memo[idx1].args == args)
return memo[idx1].res;
// FNV prime
immutable idx2 = (hash * 16_777_619) % maxSize;
if (!bt(initialized.ptr, idx2))
{
emplace(&memo[idx2], memo[idx1]);
bts(initialized.ptr, idx2);
}
else if (memo[idx2].args == args)
return memo[idx2].res;
else if (idx1 != idx2)
memo[idx2] = memo[idx1];
memo[idx1] = Value(args, fun(args));
return memo[idx1].res;
}
}
/**
* To _memoize a recursive function, simply insert the memoized call in lieu of the plain recursive call.
* For example, to transform the exponential-time Fibonacci implementation into a linear-time computation:
*/
@safe nothrow
unittest
{
ulong fib(ulong n) @safe nothrow
{
return n < 2 ? n : memoize!fib(n - 2) + memoize!fib(n - 1);
}
assert(fib(10) == 55);
}
/**
* To improve the speed of the factorial function,
*/
@safe unittest
{
ulong fact(ulong n) @safe
{
return n < 2 ? 1 : n * memoize!fact(n - 1);
}
assert(fact(10) == 3628800);
}
/**
* This memoizes all values of `fact` up to the largest argument. To only cache the final
* result, move `memoize` outside the function as shown below.
*/
@safe unittest
{
ulong factImpl(ulong n) @safe
{
return n < 2 ? 1 : n * factImpl(n - 1);
}
alias fact = memoize!factImpl;
assert(fact(10) == 3628800);
}
/**
* When the `maxSize` parameter is specified, memoize will used
* a fixed size hash table to limit the number of cached entries.
*/
@system unittest // not @safe due to memoize
{
ulong fact(ulong n)
{
// Memoize no more than 8 values
return n < 2 ? 1 : n * memoize!(fact, 8)(n - 1);
}
assert(fact(8) == 40320);
// using more entries than maxSize will overwrite existing entries
assert(fact(10) == 3628800);
}
@system unittest // not @safe due to memoize
{
import core.math : sqrt;
alias msqrt = memoize!(function double(double x) { return sqrt(x); });
auto y = msqrt(2.0);
assert(y == msqrt(2.0));
y = msqrt(4.0);
assert(y == sqrt(4.0));
// alias mrgb2cmyk = memoize!rgb2cmyk;
// auto z = mrgb2cmyk([43, 56, 76]);
// assert(z == mrgb2cmyk([43, 56, 76]));
//alias mfib = memoize!fib;
static ulong fib(ulong n) @safe
{
alias mfib = memoize!fib;
return n < 2 ? 1 : mfib(n - 2) + mfib(n - 1);
}
auto z = fib(10);
assert(z == 89);
static ulong fact(ulong n) @safe
{
alias mfact = memoize!fact;
return n < 2 ? 1 : n * mfact(n - 1);
}
assert(fact(10) == 3628800);
// https://issues.dlang.org/show_bug.cgi?id=12568
static uint len2(const string s) { // Error
alias mLen2 = memoize!len2;
if (s.length == 0)
return 0;
else
return 1 + mLen2(s[1 .. $]);
}
int _func(int x) @safe { return 1; }
alias func = memoize!(_func, 10);
assert(func(int.init) == 1);
assert(func(int.init) == 1);
}
// https://issues.dlang.org/show_bug.cgi?id=16079
// memoize should work with arrays
@system unittest // not @safe with -dip1000 due to memoize
{
int executed = 0;
T median(T)(const T[] nums) {
import std.algorithm.sorting : sort;
executed++;
auto arr = nums.dup;
arr.sort();
if (arr.length % 2)
return arr[$ / 2];
else
return (arr[$ / 2 - 1]
+ arr[$ / 2]) / 2;
}
alias fastMedian = memoize!(median!int);
assert(fastMedian([7, 5, 3]) == 5);
assert(fastMedian([7, 5, 3]) == 5);
assert(executed == 1);
}
// https://issues.dlang.org/show_bug.cgi?id=16079: memoize should work with structs
@safe unittest
{
int executed = 0;
T pickFirst(T)(T first)
{
executed++;
return first;
}
struct Foo { int k; }
Foo A = Foo(3);
alias first = memoize!(pickFirst!Foo);
assert(first(Foo(3)) == A);
assert(first(Foo(3)) == A);
assert(executed == 1);
}
// https://issues.dlang.org/show_bug.cgi?id=20439 memoize should work with void opAssign
@safe unittest
{
static struct S
{
void opAssign(S) {}
}
assert(memoize!(() => S()) == S());
}
// https://issues.dlang.org/show_bug.cgi?id=16079: memoize should work with classes
@system unittest // not @safe with -dip1000 due to memoize
{
int executed = 0;
T pickFirst(T)(T first)
{
executed++;
return first;
}
class Bar
{
size_t k;
this(size_t k)
{
this.k = k;
}
override size_t toHash()
{
return k;
}
override bool opEquals(Object o)
{
auto b = cast(Bar) o;
return b && k == b.k;
}
}
alias firstClass = memoize!(pickFirst!Bar);
assert(firstClass(new Bar(3)).k == 3);
assert(firstClass(new Bar(3)).k == 3);
assert(executed == 1);
}
// https://issues.dlang.org/show_bug.cgi?id=20302
@system unittest
{
version (none) // TODO change `none` to `all` and fix remaining limitations
struct S { const int len; }
else
struct S { int len; }
static string fun000( string str, S s) { return str[0 .. s.len] ~ "123"; }
static string fun001( string str, const S s) { return str[0 .. s.len] ~ "123"; }
static string fun010(const string str, S s) { return str[0 .. s.len] ~ "123"; }
static string fun011(const string str, const S s) { return str[0 .. s.len] ~ "123"; }
static const(string) fun100( string str, S s) { return str[0 .. s.len] ~ "123"; }
static const(string) fun101( string str, const S s) { return str[0 .. s.len] ~ "123"; }
static const(string) fun110(const string str, S s) { return str[0 .. s.len] ~ "123"; }
static const(string) fun111(const string str, const S s) { return str[0 .. s.len] ~ "123"; }
static foreach (fun; AliasSeq!(fun000, fun001, fun010, fun011, fun100, fun101, fun110, fun111))
{{
alias mfun = memoize!fun;
assert(mfun("abcdefgh", S(3)) == "abc123");
alias mfun2 = memoize!(fun, 42);
assert(mfun2("asd", S(3)) == "asd123");
}}
}
private struct DelegateFaker(F)
{
import std.typecons : FuncInfo, MemberFunctionGenerator;
// for @safe
static F castToF(THIS)(THIS x) @trusted
{
return cast(F) x;
}
/*
* What all the stuff below does is this:
*--------------------
* struct DelegateFaker(F) {
* extern(linkage)
* [ref] ReturnType!F doIt(Parameters!F args) [@attributes]
* {
* auto fp = cast(F) &this;
* return fp(args);
* }
* }
*--------------------
*/
// We will use MemberFunctionGenerator in std.typecons. This is a policy
// configuration for generating the doIt().
template GeneratingPolicy()
{
// Inform the genereator that we only have type information.
enum WITHOUT_SYMBOL = true;
// Generate the function body of doIt().
template generateFunctionBody(unused...)
{
enum generateFunctionBody =
// [ref] ReturnType doIt(Parameters args) @attributes
q{
// When this function gets called, the this pointer isn't
// really a this pointer (no instance even really exists), but
// a function pointer that points to the function to be called.
// Cast it to the correct type and call it.
auto fp = castToF(&this);
return fp(args);
};
}
}
// Type information used by the generated code.
alias FuncInfo_doIt = FuncInfo!(F);
// Generate the member function doIt().
mixin( MemberFunctionGenerator!(GeneratingPolicy!())
.generateFunction!("FuncInfo_doIt", "doIt", F) );
}
/**
* Convert a callable to a delegate with the same parameter list and
* return type, avoiding heap allocations and use of auxiliary storage.
*
* Params:
* fp = a function pointer or an aggregate type with `opCall` defined.
* Returns:
* A delegate with the context pointer pointing to nothing.
*
* Example:
* ----
* void doStuff() {
* writeln("Hello, world.");
* }
*
* void runDelegate(void delegate() myDelegate) {
* myDelegate();
* }
*
* auto delegateToPass = toDelegate(&doStuff);
* runDelegate(delegateToPass); // Calls doStuff, prints "Hello, world."
* ----
*
* BUGS:
* $(UL
* $(LI Does not work with `@safe` functions.)
* $(LI Ignores C-style / D-style variadic arguments.)
* )
*/
auto toDelegate(F)(auto ref F fp)
if (isCallable!(F))
{
static if (is(F == delegate))
{
return fp;
}
else static if (is(typeof(&F.opCall) == delegate)
|| (is(typeof(&F.opCall) V : V*) && is(V == function)))
{
return toDelegate(&fp.opCall);
}
else
{
alias DelType = typeof(&(new DelegateFaker!(F)).doIt);
static struct DelegateFields {
union {
DelType del;
//pragma(msg, typeof(del));
struct {
void* contextPtr;
void* funcPtr;
}
}
}
// fp is stored in the returned delegate's context pointer.
// The returned delegate's function pointer points to
// DelegateFaker.doIt.
DelegateFields df;
df.contextPtr = cast(void*) fp;
DelegateFaker!(F) dummy;
auto dummyDel = &dummy.doIt;
df.funcPtr = dummyDel.funcptr;
return df.del;
}
}
///
@system unittest
{
static int inc(ref uint num) {
num++;
return 8675309;
}
uint myNum = 0;
auto incMyNumDel = toDelegate(&inc);
auto returnVal = incMyNumDel(myNum);
assert(myNum == 1);
}
@system unittest // not @safe due to toDelegate
{
static int inc(ref uint num) {
num++;
return 8675309;
}
uint myNum = 0;
auto incMyNumDel = toDelegate(&inc);
int delegate(ref uint) dg = incMyNumDel;
auto returnVal = incMyNumDel(myNum);
assert(myNum == 1);
interface I { int opCall(); }
class C: I { int opCall() { inc(myNum); return myNum;} }
auto c = new C;
auto i = cast(I) c;
auto getvalc = toDelegate(c);
assert(getvalc() == 2);
auto getvali = toDelegate(i);
assert(getvali() == 3);
struct S1 { int opCall() { inc(myNum); return myNum; } }
static assert(!is(typeof(&s1.opCall) == delegate));
S1 s1;
auto getvals1 = toDelegate(s1);
assert(getvals1() == 4);
struct S2 { static int opCall() { return 123456; } }
static assert(!is(typeof(&S2.opCall) == delegate));
S2 s2;
auto getvals2 =&S2.opCall;
assert(getvals2() == 123456);
/* test for attributes */
{
static int refvar = 0xDeadFace;
static ref int func_ref() { return refvar; }
static int func_pure() pure { return 1; }
static int func_nothrow() nothrow { return 2; }
static int func_property() @property { return 3; }
static int func_safe() @safe { return 4; }
static int func_trusted() @trusted { return 5; }
static int func_system() @system { return 6; }
static int func_pure_nothrow() pure nothrow { return 7; }
static int func_pure_nothrow_safe() pure nothrow @safe { return 8; }
auto dg_ref = toDelegate(&func_ref);
int delegate() pure dg_pure = toDelegate(&func_pure);
int delegate() nothrow dg_nothrow = toDelegate(&func_nothrow);
int delegate() @property dg_property = toDelegate(&func_property);
int delegate() @safe dg_safe = toDelegate(&func_safe);
int delegate() @trusted dg_trusted = toDelegate(&func_trusted);
int delegate() @system dg_system = toDelegate(&func_system);
int delegate() pure nothrow dg_pure_nothrow = toDelegate(&func_pure_nothrow);
int delegate() @safe pure nothrow dg_pure_nothrow_safe = toDelegate(&func_pure_nothrow_safe);
//static assert(is(typeof(dg_ref) == ref int delegate())); // [BUG@DMD]
assert(dg_ref() == refvar);
assert(dg_pure() == 1);
assert(dg_nothrow() == 2);
assert(dg_property() == 3);
assert(dg_safe() == 4);
assert(dg_trusted() == 5);
assert(dg_system() == 6);
assert(dg_pure_nothrow() == 7);
assert(dg_pure_nothrow_safe() == 8);
}
/* test for linkage */
{
struct S
{
extern(C) static void xtrnC() {}
extern(D) static void xtrnD() {}
}
auto dg_xtrnC = toDelegate(&S.xtrnC);
auto dg_xtrnD = toDelegate(&S.xtrnD);
static assert(! is(typeof(dg_xtrnC) == typeof(dg_xtrnD)));
}
}
/**
* Passes the fields of a struct as arguments to a function.
*
* Can be used with a $(LINK2 https://dlang.org/spec/expression.html#function_literals,
* function literal) to give temporary names to the fields of a struct or
* tuple.
*
* Params:
* fun = Callable that the struct's fields will be passed to.
*
* Returns:
* A function that accepts a single struct as an argument and passes its
* fields to `fun` when called.
*/
template bind(alias fun)
{
/**
* Params:
* args = The struct or tuple whose fields will be used as arguments.
*
* Returns: `fun(args.tupleof)`
*/
auto ref bind(T)(auto ref T args)
if (is(T == struct))
{
import std.meta : Map = staticMap;
import core.lifetime : move;
// Forwards the i'th member of `args`
// Needed because core.lifetime.forward doesn't work on struct members
template forwardArg(size_t i)
{
static if (__traits(isRef, args) || !is(typeof(move(args.tupleof[i]))))
enum forwardArg = "args.tupleof[" ~ toCtString!i ~ "], ";
else
enum forwardArg = "move(args.tupleof[" ~ toCtString!i ~ "]), ";
}
static if (args.tupleof.length == 0)
enum argList = "";
else
alias argList = Map!(forwardArg, Iota!(args.tupleof.length));
return mixin("fun(", argList, ")");
}
}
/// Giving names to tuple elements
@safe unittest
{
import std.typecons : tuple;
auto name = tuple("John", "Doe");
string full = name.bind!((first, last) => first ~ " " ~ last);
assert(full == "John Doe");
}
/// Passing struct fields to a function
@safe unittest
{
import std.algorithm.comparison : min, max;
struct Pair
{
int a;
int b;
}
auto p = Pair(123, 456);
assert(p.bind!min == 123); // min(p.a, p.b)
assert(p.bind!max == 456); // max(p.a, p.b)
}
/// In a range pipeline
@safe unittest
{
import std.algorithm.iteration : map, filter;
import std.algorithm.comparison : equal;
import std.typecons : tuple;
auto ages = [
tuple("Alice", 35),
tuple("Bob", 64),
tuple("Carol", 21),
tuple("David", 39),
tuple("Eve", 50)
];
auto overForty = ages
.filter!(bind!((name, age) => age > 40))
.map!(bind!((name, age) => name));
assert(overForty.equal(["Bob", "Eve"]));
}
// Zero arguments
@safe unittest
{
struct Empty {}
assert(Empty().bind!(() => 123) == 123);
}
// Non-copyable arguments
@safe unittest
{
import std.typecons : tuple;
static struct NoCopy
{
int n;
@disable this(this);
}
static struct Pair
{
NoCopy a, b;
}
static auto fun(NoCopy a, NoCopy b)
{
return tuple(a.n, b.n);
}
auto expected = fun(NoCopy(1), NoCopy(2));
assert(Pair(NoCopy(1), NoCopy(2)).bind!fun == expected);
}
// ref arguments
@safe unittest
{
import std.typecons : tuple;
auto t = tuple(123, 456);
t.bind!((ref int a, int b) { a = 789; b = 1011; });
assert(t[0] == 789);
assert(t[1] == 456);
}
// auto ref arguments
@safe unittest
{
import std.typecons : tuple;
auto t = tuple(123);
t.bind!((auto ref x) {
static assert(__traits(isRef, x));
});
tuple(123).bind!((auto ref x) {
static assert(!__traits(isRef, x));
});
}