Old NELWIN

Main Page

Overview

Simple Maple

Recursive Maple

Object Maple

Random Numbers

See also:
Report 1996

Introduction

In the present context, object-oriented programming can, with some right, be translated to actor-oriented programming. This means, that the units of the program are actors who react upon key words. These 'Requests' are names starting with a capital letter, like 'Supply', 'InvestmentDemand', 'Decide', etc. The requests may be supplemented by one or more arguments of importance for the response to the request. These arguments are names without an initial capital letter (except in the case of the standard names for the state variables: A and K).

All actors have to be created explicitly. The initial group of actors is created at the start of the computation but later new actors (firms) may emerge as the result of entrepreneurial activity. In order to create an actor, the creating procedure must be supplied with a sequence of parameter values which determine much of the behaviour of the actor. Later some actors may, however, change their behavioural pattern because of their decisions to change the rules underlying their behaviour.

An example procedure

CreateFirm := proc()

local Firm;

	Firm := subs(
		{args},
		proc(Request)
		local A, actualMarkUp, deprCapital, desCapital, desFinance,
			desMarkUp, expandContract, externalFinance, I_act, I_des,
			I-max, imiEffort, info, innoEffort, K, Lottery,
			marketShare, price, priceLid, profit, supply, targetMarkUp;

			A := proc()
			option remember;
			end;
			K := proc()
			option remember;
			end;

		# InitialiseState
			if Request = InitialiseState then
				A() := A_init;
				K() := K_init;

		# Supply (and change technology)
			elif Request = Supply then
				supply := A()*K();
				innoEffort := d_in*r_in*K();
				A(in) := TechnoSpace(Decide, innoEffort, A());
				imiEffort := d_im*r_im*K();
				A(im) := max(seq
                                   (Firm.i(TechnoInfo, country, imiEffort),i = 1..n));
				A(next) := max(A(), A(in), A(im));
				RETURN(supply);

		# InvestmentDemand
			elif Request = InvestmentDemand then
				totalSupply := args[2];
				price := args[3];
				profit := price*A()*K() - (c + r_in + r_im)*K();
				marketShare := A()*K()/totalSupply;
				targetMarkUp := eta + (1 - marketShare)*psi/
						(eta + (1 - marketShare)*psi - marketShare);
				priceLid := .999*(price + P_max)*A(next)/(2*c);
				desMarkUp := min(targetMarkUp, priceLid);
				actualMarkUp := price/(c/A(next));
				expandContract := 1 - desMarkUp/actualMarkUp;
				desCapital := K()*(1 + expandContract);
				deprCapital := K()*(1 - delta);
				I_des := desCapital - deprCapital;
				desFinance := I_des - profit - delta;
				externalFinance := 
					FinancialSector(Decide, desFinance, profit, K());
				if externalFinance = bankruptcy then
					A() := 0;
					K() := 0;
				else
					I_max := delta + profit + externalFinance;
					I_act := max(0, min(I_des, I_max));
					K() := K()*(1 - delta) + I_act;
					A() := A(next);
				fi;

		# OfficialStats
			elif Request = OfficialStats then
				RETURN(A(), K());
			fi;
		end);

	Firm(InitialiseState);

	RETURN(op(Firm));

end;

Other procedures

• TechnoSpace which can be requested to Initialise and to Decide about the outcome of a firm search.
• HouseholdSector which reacts to the output of firms.
• FinancialSector which reacts to the financial requests of firms.
• StatisticalOffice which collects information which can be analysed by researchers.