How to explicitly mark an instance of frontend.Variable as constant, or create so?

[weijiguo]

The data may have been processed somehow, hex-decoding, type conversion, etc. For example, we need to supply a Domain Separation Tag when calculating the HashToG2 function. We need to make this dst a constant and ensure that its value impacts the circuit structure, rather than a witness which could be replaced with another value without impacting the circuit structure.

[gbotrel]

hi -- anything you pass to an frontend.API will be a constant (if it's not a variable :)). So:

api.Mul(1,2)
a := big.NewInt(...)
api.Mul(a, 2)

are all constant params.

[weijiguo]

Thanks, that's simple enough. I used to program with Arkworks and got used to creating a constant.