Obtaining real-time solutions to non-linear programming problems is required in some engineering systems. Recently, a special circuit has been proposed that allows one to solve such problems by analogue simulation. This circuit is made of ideal diodes, non-linear VCCSs and non-linear CCVSs, and is capable of simulating any non-linear programming problem in a systematic way. The purpose in this paper is to show that there exist other circuits that exhibit the same remarkable properties and hence can also be used to solve any non-linear programming problems. The new circuits are canonic in the same sense as the above circuits, but two of them require only one type of controlled source, thus making these circuits more attractive from an implementation point of view.