rust - How do I implement commutative (scalar) multiplication with a built-in type like `f64`? -

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i'd implement commutative scalar f64 multiplication operation using * operator. implementing mul<f64> trait type gives me right side multiplication like.

struct foo(f64);  impl mul<f64> foo {     type output = foo;      fn mul(self, _rhs: f64) -> foo {         // implementation     } }  let = foo(1.23); * 3.45; // works 3.45 * a; // error: trait bound `{float}: std::ops::mul<foo>` not satisfied [e0277]

for non-builtin scalar type, can implement same trait other way round on scalar, i.e. implementing mul<foo> on scalar type.

how left side implementation built-in type f64 too?

you can reverse implementation, swapping f64 foo

impl std::ops::mul<foo> f64 {     type output = foo;      fn mul(self, rhs: foo) -> foo {         rhs * self     } }

try out in playground


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