Conditionals statements in circuit definition

[gbotrel]

In an imperative programming language, that would be a if / else.

However, it doesn't translate well in a declarative API to define the circuit, as the output of the frontend.Compile method is an arithmetic representation that must encode the various branches.

gnark offers cs.Select(...) API, which is similar to Prolog-like languages.

// Select if b is true, yields i1 else yields i2
func (cs *ConstraintSystem) Select(b Variable, i1, i2 interface{}) Variable {

At a minimum, gnark should provide some syntactic sugar to wrap several instructions, maybe in a lambda, into a a if-like statement.

[SherLzp]

Recently wants to use it, could you give some ideas about how to add if in circuit?

[gbotrel]

hi @SherLzp --> there is a branch, a bit outdated to explore some ideas: https://github.com/ConsenSys/gnark/tree/feat/conditional

this is going to get some attention quite soon, but first we have some PlonK efficiency work on the plate.

[gbotrel]

in particular: https://github.com/ConsenSys/gnark/blob/feat/conditional/internal/backend/circuits/conditional.go

[SherLzp]

Noted. Thanks

[SherLzp]

When will this issue be implemented? @gbotrel