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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.
Parameters
Name | Description |
---|---|
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
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
License
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