mirror of
https://github.com/dlang/phobos.git
synced 2025-04-29 14:40:30 +03:00
512 lines
14 KiB
D
512 lines
14 KiB
D
// Written in the D programming language.
|
|
|
|
/**
|
|
Functions that manipulate other functions.
|
|
|
|
Macros:
|
|
|
|
WIKI = Phobos/StdFunctional
|
|
|
|
Author:
|
|
|
|
$(WEB erdani.org, Andrei Alexandrescu)
|
|
*/
|
|
|
|
/*
|
|
* Copyright (C) 2004-2006 by Digital Mars, www.digitalmars.com
|
|
* Written by Andrei Alexandrescu, www.erdani.org
|
|
*
|
|
* This software is provided 'as-is', without any express or implied
|
|
* warranty. In no event will the authors be held liable for any damages
|
|
* arising from the use of this software.
|
|
*
|
|
* Permission is granted to anyone to use this software for any purpose,
|
|
* including commercial applications, and to alter it and redistribute it
|
|
* freely, subject to the following restrictions:
|
|
*
|
|
* o The origin of this software must not be misrepresented; you must not
|
|
* claim that you wrote the original software. If you use this software
|
|
* in a product, an acknowledgment in the product documentation would be
|
|
* appreciated but is not required.
|
|
* o Altered source versions must be plainly marked as such, and must not
|
|
* be misrepresented as being the original software.
|
|
* o This notice may not be removed or altered from any source
|
|
* distribution.
|
|
*/
|
|
|
|
module std.functional;
|
|
|
|
import std.metastrings, std.stdio, std.traits, std.typecons, std.typetuple;
|
|
// for making various functions visible in *naryFun
|
|
import std.algorithm, std.contracts, std.conv, std.math, std.range, std.string;
|
|
|
|
/**
|
|
Transforms a string representing an expression into a unary
|
|
function. The string must use symbol name $(D a) as the parameter.
|
|
|
|
Example:
|
|
|
|
----
|
|
alias unaryFun!("(a & 1) == 0") isEven;
|
|
assert(isEven(2) && !isEven(1));
|
|
----
|
|
*/
|
|
|
|
template unaryFun(alias funbody, bool byRef = false, string parmName = "a")
|
|
{
|
|
alias unaryFunImpl!(funbody, byRef, parmName).result unaryFun;
|
|
}
|
|
|
|
template unaryFunImpl(alias fun, bool byRef, string parmName = "a")
|
|
{
|
|
static if (is(typeof(fun) : string))
|
|
{
|
|
template Body(ElementType)
|
|
{
|
|
enum testAsExpression = "{"~ElementType.stringof
|
|
~" "~parmName~"; return ("~fun~");}()";
|
|
enum testAsStmts = "{"~ElementType.stringof
|
|
~" "~parmName~"; "~fun~"}()";
|
|
// pragma(msg, "Expr: "~testAsExpression);
|
|
// pragma(msg, "Stmts: "~testAsStmts);
|
|
static if (__traits(compiles, mixin(testAsExpression)))
|
|
{
|
|
enum string code = "return (" ~ fun ~ ");";
|
|
alias typeof(mixin(testAsExpression)) ReturnType;
|
|
}
|
|
// else static if (__traits(compiles, mixin(testAsStmts)))
|
|
// {
|
|
// enum string code = fun;
|
|
// alias typeof(mixin(testAsStmts)) ReturnType;
|
|
// }
|
|
else
|
|
{
|
|
// Credit for this idea goes to Don Clugston
|
|
// static assert is a bit broken,
|
|
// better to do it this way to provide a backtrace.
|
|
// pragma(msg, "Bad unary function: " ~ fun ~ " for type "
|
|
// ~ ElementType.stringof);
|
|
static assert(false, "Bad unary function: " ~ fun ~
|
|
" for type " ~ ElementType.stringof);
|
|
}
|
|
}
|
|
static if (byRef)
|
|
{
|
|
Body!(ElementType).ReturnType result(ElementType)(ref ElementType a)
|
|
{
|
|
mixin(Body!(ElementType).code);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
Body!(ElementType).ReturnType result(ElementType)(ElementType __a)
|
|
{
|
|
mixin("alias __a "~parmName~";");
|
|
mixin(Body!(ElementType).code);
|
|
}
|
|
// string mixme = "Body!(ElementType).ReturnType"
|
|
// " result(ElementType)(ElementType a)
|
|
// { " ~ Body!(ElementType).code ~ " }";
|
|
// mixin(mixme);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
alias fun result;
|
|
}
|
|
}
|
|
|
|
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);
|
|
}
|
|
|
|
/**
|
|
Transforms a string representing an expression into a Boolean binary
|
|
predicate. The string must use symbol names $(D a) and $(D b) as the
|
|
compared elements.
|
|
|
|
Example:
|
|
|
|
----
|
|
alias binaryFun!("a < b") less;
|
|
assert(less(1, 2) && !less(2, 1));
|
|
alias binaryFun!("a > b") greater;
|
|
assert(!greater("1", "2") && greater("2", "1"));
|
|
----
|
|
*/
|
|
|
|
template binaryFun(alias funbody, string parm1Name = "a",
|
|
string parm2Name = "b")
|
|
{
|
|
alias binaryFunImpl!(funbody, parm1Name, parm2Name).result binaryFun;
|
|
}
|
|
|
|
template binaryFunImpl(alias fun,
|
|
string parm1Name, string parm2Name)
|
|
{
|
|
static if (is(typeof(fun) : string))
|
|
{
|
|
template Body(ElementType1, ElementType2)
|
|
{
|
|
enum testAsExpression = "{"~ElementType1.stringof
|
|
~" "~parm1Name~"; "~ElementType2.stringof
|
|
~" "~parm2Name~"; return ("~fun~");}()";
|
|
enum testAsStmts = "{"~ElementType1.stringof
|
|
~" "~parm1Name~"; "~ElementType2.stringof
|
|
~" "~parm2Name~"; "~fun~"}()";
|
|
static if (__traits(compiles, mixin(testAsExpression)))
|
|
{
|
|
enum string code = "return (" ~ fun ~ ");";
|
|
alias typeof(mixin(testAsExpression)) ReturnType;
|
|
}
|
|
// else static if (__traits(compiles, mixin(testAsStmts)))
|
|
// {
|
|
// enum string code = fun;
|
|
// alias typeof(mixin(testAsStmts)) ReturnType;
|
|
// }
|
|
else
|
|
{
|
|
// Credit for this idea goes to Don Clugston
|
|
enum string msg =
|
|
"Bad binary function q{" ~ fun ~ "}."
|
|
~" You need to use a valid D expression using symbols "
|
|
~parm1Name~" of type "~ElementType1.stringof~" and "
|
|
~parm2Name~" of type "~ElementType2.stringof~"."
|
|
~(fun.length && fun[$ - 1] == ';'
|
|
? " The trailing semicolon is _not_ needed."
|
|
: "")
|
|
~(fun.length && fun[$ - 1] == '}'
|
|
? " The trailing bracket is mistaken."
|
|
: "");
|
|
static assert(false, msg);
|
|
}
|
|
}
|
|
Body!(ElementType1, ElementType2).ReturnType
|
|
result(ElementType1, ElementType2)
|
|
(ElementType1 __a, ElementType2 __b)
|
|
{
|
|
mixin("alias __a "~parm1Name~";");
|
|
mixin("alias __b "~parm2Name~";");
|
|
mixin(Body!(ElementType1, ElementType2).code);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
alias fun result;
|
|
}
|
|
// static if (is(typeof(comp) : string))
|
|
// {
|
|
// // @@@BUG1816@@@: typeof(mixin(comp)) should work
|
|
// typeof({
|
|
// static ElementType1 a;
|
|
// static ElementType2 b;
|
|
// return mixin(comp);
|
|
// }())
|
|
// binaryFun(ElementType1, ElementType2)
|
|
// (ElementType1 a, ElementType2 b)
|
|
// {
|
|
// return mixin(comp);
|
|
// }
|
|
// }
|
|
// else
|
|
// {
|
|
// alias comp binaryFun;
|
|
// }
|
|
}
|
|
|
|
unittest
|
|
{
|
|
alias binaryFun!(q{a < b}) less;
|
|
assert(less(1, 2) && !less(2, 1));
|
|
assert(less("1", "2") && !less("2", "1"));
|
|
|
|
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);
|
|
}
|
|
|
|
/*
|
|
Predicate that returns $(D_PARAM a < b).
|
|
*/
|
|
//bool less(T)(T a, T b) { return a < b; }
|
|
//alias binaryFun!(q{a < b}) less;
|
|
|
|
/*
|
|
Predicate that returns $(D_PARAM a > b).
|
|
*/
|
|
//alias binaryFun!(q{a > b}) greater;
|
|
|
|
/*
|
|
Predicate that returns $(D_PARAM a == b).
|
|
*/
|
|
//alias binaryFun!(q{a == b}) equalTo;
|
|
|
|
/*
|
|
Binary predicate that reverses the order of arguments, e.g., given
|
|
$(D pred(a, b)), returns $(D pred(b, a)).
|
|
*/
|
|
template binaryRevertArgs(alias pred)
|
|
{
|
|
typeof({ ElementType1 a; ElementType2 b; return pred(b, a);}())
|
|
binaryRevertArgs(ElementType1, ElementType2)(ElementType1 a, ElementType2 b)
|
|
{
|
|
return pred(b, a);
|
|
}
|
|
}
|
|
|
|
unittest
|
|
{
|
|
alias binaryRevertArgs!(binaryFun!("a < b")) gt;
|
|
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 binaryRevertArgs!(foo) zyx;
|
|
assert(zyx(5, 4) == foo(4, 5));
|
|
}
|
|
|
|
/**
|
|
Negates predicate $(D pred).
|
|
|
|
Example:
|
|
----
|
|
string a = " Hello, world!";
|
|
assert(find!(not!isspace)(a) == "Hello, world!");
|
|
----
|
|
*/
|
|
template not(alias pred)
|
|
{
|
|
bool not(T...)(T args) { return !pred(args); }
|
|
}
|
|
|
|
/**
|
|
Curries $(D fun) by tying its first argument to a particular value.
|
|
|
|
Example:
|
|
|
|
----
|
|
int fun(int a, int b) { return a + b; }
|
|
assert(curry!(fun, 5)(6) == 11);
|
|
----
|
|
*/
|
|
template curry(alias fun, alias arg)
|
|
{
|
|
ReturnType!fun curry(ParameterTypeTuple!(fun)[1] arg2)
|
|
{
|
|
return fun(arg, arg2);
|
|
}
|
|
}
|
|
|
|
unittest
|
|
{
|
|
static int f1(int a, int b) { return a + b; }
|
|
assert(curry!(f1, 5)(6) == 11);
|
|
int x = 5;
|
|
int f2(int a, int b) { return a + b; }
|
|
assert(curry!(f2, x)(6) == 11);
|
|
auto f3 = &curry!(f2, x);
|
|
assert(f3(6) == 11);
|
|
}
|
|
|
|
/*private*/ template Adjoin(F...)
|
|
{
|
|
template For(V...)
|
|
{
|
|
static if (F.length == 0)
|
|
{
|
|
alias TypeTuple!() Result;
|
|
}
|
|
else
|
|
{
|
|
alias F[0] headFun;
|
|
alias typeof({ V values; return headFun(values); }()) Head;
|
|
alias TypeTuple!(Head, Adjoin!(F[1 .. $]).For!(V).Result) Result;
|
|
}
|
|
|
|
Tuple!(Result) fun(V...)(V a)
|
|
{
|
|
typeof(return) result;
|
|
foreach (i, Unused; Result)
|
|
{
|
|
result.field[i] = F[i](a);
|
|
}
|
|
return result;
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
Takes multiple functions and adjoins them together. The result is a
|
|
$(XREF typecons, Tuple) with one element per passed-in function. Upon
|
|
invocation, the returned tuple is the adjoined results of all
|
|
functions.
|
|
|
|
Example:
|
|
|
|
----
|
|
static bool f1(int a) { return a != 0; }
|
|
static int f2(int a) { return a / 2; }
|
|
auto x = adjoin!(f1, f2)(5);
|
|
assert(is(typeof(x) == Tuple!(bool, int)));
|
|
assert(x._0 == true && x.field[1] == 2);
|
|
----
|
|
*/
|
|
template adjoin(F...)
|
|
{
|
|
Tuple!(Adjoin!(F).For!(V).Result) adjoin(V...)(V a)
|
|
{
|
|
typeof(return) result;
|
|
foreach (i, Unused; Adjoin!(F).For!(V).Result)
|
|
{
|
|
result.field[i] = F[i](a);
|
|
}
|
|
return result;
|
|
}
|
|
}
|
|
|
|
unittest
|
|
{
|
|
static bool F1(int a) { return a != 0; }
|
|
static int F2(int a) { return a / 2; }
|
|
auto x = adjoin!(F1, F2)(5);
|
|
alias Adjoin!(F1, F2).For!(int).Result R;
|
|
assert(is(typeof(x) == Tuple!(bool, int)));
|
|
assert(x.field[0] && x.field[1] == 2);
|
|
}
|
|
|
|
// /*private*/ template NaryFun(string fun, string letter, V...)
|
|
// {
|
|
// static if (V.length == 0)
|
|
// {
|
|
// enum args = "";
|
|
// }
|
|
// else
|
|
// {
|
|
// enum args = V[0].stringof~" "~letter~"; "
|
|
// ~NaryFun!(fun, [letter[0] + 1], V[1..$]).args;
|
|
// enum code = args ~ "return "~fun~";";
|
|
// }
|
|
// alias void Result;
|
|
// }
|
|
|
|
// unittest
|
|
// {
|
|
// writeln(NaryFun!("a * b * 2", "a", int, double).code);
|
|
// }
|
|
|
|
// /**
|
|
// naryFun
|
|
// */
|
|
// template naryFun(string fun)
|
|
// {
|
|
// //NaryFun!(fun, "a", V).Result
|
|
// int naryFun(V...)(V values)
|
|
// {
|
|
// enum string code = NaryFun!(fun, "a", V).code;
|
|
// mixin(code);
|
|
// }
|
|
// }
|
|
|
|
// unittest
|
|
// {
|
|
// alias naryFun!("a + b") test;
|
|
// test(1, 2);
|
|
// }
|
|
|
|
/**
|
|
Composes passed-in functions $(D fun[0], fun[1], ...) returning a
|
|
function $(D f(x)) that in turn returns $(D
|
|
fun[0](fun[1](...(x)))...). Each function can be a regular
|
|
functions, a delegate, or a string.
|
|
|
|
Example:
|
|
|
|
----
|
|
// 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") == [1, 2, 3]);
|
|
----
|
|
*/
|
|
|
|
template compose(fun...) { alias composeImpl!(fun).doIt compose; }
|
|
|
|
// Implementation of compose
|
|
template composeImpl(fun...)
|
|
{
|
|
static if (fun.length == 2)
|
|
{
|
|
// starch
|
|
static if (is(typeof(fun[0]) : string))
|
|
alias unaryFun!(fun[0]) fun0;
|
|
else
|
|
alias fun[0] fun0;
|
|
static if (is(typeof(fun[1]) : string))
|
|
alias unaryFun!(fun[1]) fun1;
|
|
else
|
|
alias fun[1] fun1;
|
|
// protein: the core composition operation
|
|
typeof({ E a; return fun0(fun1(a)); }()) doIt(E)(E a)
|
|
{
|
|
return fun0(fun1(a));
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// protein: assembling operations
|
|
alias composeImpl!(fun[0], composeImpl!(fun[1 .. $]).doIt).doIt doIt;
|
|
}
|
|
}
|
|
|
|
/**
|
|
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.
|
|
|
|
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");
|
|
----
|
|
*/
|
|
|
|
template pipe(fun...)
|
|
{
|
|
alias compose!(Reverse!(fun)) pipe;
|
|
}
|
|
|
|
unittest
|
|
{
|
|
// 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);
|
|
|
|
// @@@BUG@@@
|
|
//assert(compose!(baz, bar)("1") == 2.5);
|
|
|
|
// @@@BUG@@@
|
|
//assert(compose!(`a + 0.5`, `to!(int)(a) + 1`, foo)(1) == 2.5);
|
|
}
|