The function setup(C) constructs a set of equations in a form with isolated variables on the left-hand side. Those variables form a basis for the corresponding linear system, and do not occur on the right hand side of any equation. Slack variables of the form _SL.i are introduced to deal with inequalities. Unrestricted variables are transformed to be the difference of two variables.

The resulting system is equivalent to the original system C, in that solutions to the new system can be transformed into solutions of the original system. The resulting system need not correspond to a feasible basic solution.

If the optional second parameter 'NONNEGATIVE' is present, all variables are assumed to be non-negative.  If a third parameter is present, then it is assigned the transformations used for any variable deemed to be unrestricted.

The command with(simplex,setup) allows the use of the abbreviated form of this command.

$\mathrm{with}\left(\mathrm{simplex}\right)\:$

$\mathrm{setup}\left(\left\{3x+4y\le 4\,4x+3y=5\right\}\right)$

$\left\{\mathrm{\_SL2}=-\frac{8}{3}+\frac{7x}{3}\,y=-\frac{4x}{3}+\frac{5}{3}\right\}$