arithmetic

CVXPy visitors for arithmetic expressions.

Visitors: Add, Sub, Mul, Div, MatMul, Neg, Power

Lowers the arithmetic AST nodes to CVXPy expressions that build the convex subproblem. Add, Sub, and Neg are affine and always DCP; Mul, Div, MatMul, and Power are admitted structurally but are only disciplined-convex under the usual conditions (one operand constant, a valid exponent), which CVXPy verifies when the problem is assembled rather than here.