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Alias std.functional.pipe

Pipes functions in sequence. Offers the same functionality as 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.

alias pipe(fun...) = compose!(Reverse!fun);

Parameters

NameDescription
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

compose

Example

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; }
writeln(compose!(baz, bar, foo)(1)); // 2.5
writeln(pipe!(foo, bar, baz)(1)); // 2.5

writeln(compose!(baz, `to!(int)(a) + 1`, foo)(1)); // 2.5
writeln(compose!(baz, bar)("1"[])); // 2.5

writeln(compose!(baz, bar)("1")); // 2.5

writeln(compose!(`a + 0.5`, `to!(int)(a) + 1`, foo)(1)); // 2.5
}

/**
* <a href="https://en.wikipedia.org/wiki/Memoization">Memoizes</a> 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 <a href="http://docs.google.com/viewer?url=http%3A%2F%2Fhop.perl.plover.com%2Fbook%2Fpdf%2F03CachingAndMemoization.pdf">this book chapter</a>.

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);

Authors

Andrei Alexandrescu

License

Boost License 1.0.