Amazing brand spanking new programming concept: Parameter Paths!

[TheHamster via Digitalmars-d]

Parameter paths, a thousand words summed up:

void foo(p1, p2|p3|p4, p5|p6, |*p7|p8){ ... }

Parameter paths provide a very simple way to express multiple 
parameter paths for a function.

It is similar but not the same as operator overloading.

Essentially, a symbol such as '|' is used to separate possible 
parameter paths in the signature of the function.

foo is essentially represented by the following functions:

void foo1(p1, p2, p5)
void foo4(p1, p3, p6, p7)
void foo4(p1, p8)

Writing foo a bit more verbose makes this clear:

void foo(|p1| | |, |p2|p3|p4|, |p5|p6| |, | |*p7|p8|)

which, if we associate entries,

|p1|   |  |
|p2| p3|p4|
|p5| p6|  |
|  |*p7|p8|


Whats interesting is that one can see these as matrix like 
functions(On the input space, rather than vectors as usual).

For this to work for functions. Each "path" must provide a 
distinct/unique "type" path. This is easily verifiable by the 
compiler as it can easily work out the type path(which is just 
the parameter paths but with types).



In some cases this allows one to present fewer arguments to the 
user.

e.g., instead of foo(p1,p2,p3,p4,p5,p6,p7,p8) we can use any of 
the "alias" above.

Essentially it could reduce overhead of writing common sets of 
overloaded functions.

e.g.,

[Overloading]
int Max(int a, int b) {...}
float Max(float a, float b) {...}

vs

[Templates]
T Max(T a, T b) if (is(T == float) || is(T == int)  { return (a < 
b) ? b : a; }


vs

[Parameter Paths]
auto Max(int a|float a, int b|float b) { return (a < b) ? b : a; }


Note that no constraints are needed, and only one function is 
required. Also note has much easier it is to maintain the 
Parameter Path'ed version. If one wants to add the ability to use 
doubles, it requires two changes, not one.

Note that with parameter paths, the same parameter name can be 
used since different types produce different functions.



I'm sure it's not worth the trouble of adding to D but maybe it 
will lead to bigger and brighter things!