use case for "alias this"

[spir]

Hello,

For what it's worth, I have finally found one use case for the famous "alias 
this" trick for structs:

struct ScienceConstant {
     float value;
     string name;
     alias value this;
     string toString () { return this.name; }
}

unittest {
     auto PI = ScienceConstant(3.14, "pi");
     writefln("%s/3 = %s", PI, PI/3);
     // --> pi/3 = 1.04667
}

For people who don't know it: the point is that "alias this" implicitely 
delegates messages (here requests for arithmetic operations) to the actual 
element (here value) on which they should apply, that happens to be embedded in 
a struct object. Or rather: that's how I conceive this feature.

Denis
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