Primitive Operators and Properties

From Nova Documentation
Jump to: navigation, search

The Properties/Primops list is correct as of Release 12, which became available on March 31, 2014
Primops added subsequently are identified by the version number in which they first appeared.

Nova supports a large set of primitives divided into properties and primitive operators, or primops.

A property is an identifier assigned a value at the beginning of a simulation run which is not expected to change. For example, the rows and cols properties of a CellMatrix are fixed at the start of a run and don’t change. A special type of property, called a state object, is used to look up the current values of components.

Primops are functions of zero or more arguments. Some primitives may be used without restriction; others make sense only in specific contexts; for example rows and cols are only useful in spatial contexts such as CellMatrices, AgentVectors and SimWorlds.

Here are the properties and primops supported by the current Nova implementation, organized by type and area of applicability. All properties begin with a lower case letter, state objects begin with a capital letter, and primops are composed entirely of capital letters. Primops are always functions, and therefore require an argument list (even if empty) in order to be invoked.

Notation: x, y represent values (numbers or string constants or expressions); fn represents a Javascript function; exp represents a string expression; [x, y] represents one or more optional arguments.

Universal Properties and Primops

These can be used in any expression in any component.

Properties

Self
The state object of the enclosing simulator (Capsule, CellMatrix, etc.) Used to look up component values (see the section on state objects, coming soon).

Control Primops

ALERT(s)
Displays message s in a dialog box.
COUNT(fn, l)
fn is a boolean function of one argument and a l is list.
Returns: COUNT(f, l) applies f to each element of l and returns the number of times the result is true.
DATA_RECORDING()
Returns: the current Data Recording Interval. This is the number of simulation steps between the posting of model data to displays (i.e. graphs and tables). This primop can be used to insert the same interval into data saved to files. The Data Recording Interval is set using the Tools | Data Recording Interval ... menu item. Default value is 1. As of version 13.4.2.
DELAY(comp, x, [y])
Returns: the value of component comp delayed by x time units. Comp is a string naming a stateful component (i.e., stock, variable or sequence).
Optional y is returned if the current time is less than x. If y is omitted then 0 is returned.
PULSE(amount, start, interval)
Returns: amount when current time is start, start + interval, start + 2*interval, etc.; 0 otherwise
STEP(x, y)
Returns: the value of x if the current time is y or greater; 0 otherwise.
TERMINATE()
Terminates the running simulation
TOTAL(fn, l)
fn is a numerical function of one argument and a l is list.
Returns: TOTAL(fn, l) applies fn to each element of l and returns the sum of the results.

Convenience Primops

These primops perform useful functions that could otherwise be programmed.

FLIP(p)
Simulates a Bernoulli trial.
Returns: true with probability p and false with probability 1-p.
Available as of release 12.1.

Input/Output Primops

BASEDIR()
Returns: the current model directory.
LOAD(l)
l is a list of JavaScript or NovaScript filenames contained in the current model directory. Each is loaded into the runtime system. Should be part of simulation initialization.

In each of the following path designates a textfile. if path begins with “/” it is treated as an absolute pathname; otherwise it is treated as relative to the current model directory.

OPENREAD(path)
Opens path for reading and returns a Java BufferedReader object. The latter contains methods read and readLine to perform input. See http://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html for complete details.
OPENWRITE(path)
Opens path for writing and returns a Java PrintWriter object. The latter contains methods print and println to perform output. See http://docs.oracle.com/javase/7/docs/api/java/io/PrintWriter.html for complete details.
READFILE(path)
Returns: the content of the file path as a string.

Mathematical Primops

BINOMIAL(n, p)
n is an integer; 0 ≤ p ≤ 1
Returns: a random number from the binomial distribution with n trials and success probability p.
COS(x)
Returns: the trigonometric cosine of x.
COSWAVE(x, y)
Returns: x*cos(2πt/y), where t is the current time.
DERIVN(fn, n)
Returns: the value of the nth derivative of fn at the current time, with precision based on the value of dt.
DISTANCE(x0, y0, x1, y1)
Returns: Euclidean distance between points (x0, y0) and (x1, y1).
Math.XXX
The JavaScript Math functions and constants; see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math.
MULTIBINOMIAL(n, p, k)
Returns: Sum of k independent executions of BINOMIAL(n, p).
MULTINOMIAL(n, [p0, p1, ... pm])
Returns: an m-element vector of outcomes from performing n independent generalized Bernoulli trials. As of Version 13.5.
NORMAL(x, y)
Returns: a random number from the normal distribution with mean x and standard deviation y.
POISSON(lambda)
Returns: a random number from the Poisson distribution with density lambda.
RANDOM()
Returns: a uniformly distributed random number between 0 and 1.
SEED(x)
Returns: nothing; sets the seed of the random number generator. Should be part of simulation initialization.
SIN(x)
Returns: the trigonometric sin of x.
SINWAVE(x, y)
Returns: x*sin(2πt/y), where t is the current time.
UNIFORM(x, y)
Returns: a uniformly distributed random variable between x and y.

Matrix Primops

COLUMNSPLIT(tab)
tab is a 2-dimensional array derived from a table, where the first row contains column headers.
Returns: an object in which each property name is a column header with property value an array comprising the corresponding column.
CSVTOMAT(csv)
csv is a string where line is a comma separated sequence of values.
Returns: the matrix in which each row corresponds to a line in csv.
ROWSTOOBJS(tab)
tab is a 2-dimensional array derived from a table, where the first row contains column headers.
Returns: an array of objects, one for each non-header row. In each object properties are column headers bound to the entry for that column in the corresponding row.
TRANSPOSE(mat)
mat is a matrix (i.e. 2-dimensional array)
Returns: the transpose of mat.

Simulation Primops

CLOCK()
Returns the current clock as an object.
DT()
Returns: current delta value (dt).
SIMSTART()
SIMEND()
SIMMETHOD()
Returns: simulation start time, end time and integration method, respectively.
TIME()
Returns: current simulation time.

Miscellaneous Primops

RECONFIGURE(agg, map)
agg must refer either to an AgentVector, SimWorld, or NetWorld, and map must be an object with property names matching initializable components in the agg agent capsule (i.e., properties or stocks). Each property name must be bound to an array of values, with each array at least as long a the initial agent count in agg. RECONFIGURE reconfigures the initial AgentVector in agg by rebinding each of the properties named in map, matching the agg agent vector to the values in the array bound to that property in map.
_.XXX
The underscore.js library of useful functions. See http://underscorejs.org.

Clocked Chip Primops

The following may only be used by a capsule in a Clocked Chip.

SUPERCLOCK()
Returns: the clock associated with the container of the Clocked Chip.
SUPERTIME()
Returns: the model time of the container of the Clocked Chip.

Cell Properties and Primops

The following may only be used by capsules contained in a CellMatrix, or cell capsule in a SimWorld. row and col are integers representing row-column coordinates within the CellMatrix. coords is a Coords object As of Release 12 all primops expecting coordinate pairs as parameters can either be called with separate row-column arguments or with a Coords object.

Cartesian coordinates will generally be automatically wrapped; i.e. if the coordinate space has dimension rows x cols, then a negative value for row or col is treated respectively as rows + row and cols + col. Values that exceed the dimensions respectively become row – rows and col – cols. This type of space is topologically equivalent to a torus.

Neighborhood function BLOCK and RING come in two versions, one that includes wrapping (WBLOCK and WRING), and one that treats the edges as boundaries (BLOCK and RING).

Properties

coords
Object whose row and col properties respectively reference the caller’s row and column coordinates within the CellMatrix.
rows
cols
Bound to the total number of rows and columns, respectively.
Super
The state object of the enclosing container.

Primops

BLOCK(n)
WBLOCK(n)
Returns: a list (array) of coordinate objects (i.e., containing row and col properties) comprising the square block of cells n units away from the caller or less. (WBLOCK is the “wrapped” version, which treats the surface as a torus).
CELL(row, col)
CELL(coords)
Returns the state object for the cell at the given coordinates, which may be passed either as separate parameters or in a coords object. The fields of the state object bind each of the Stocks, Terms and Flows in the cell to the current value of the corresponding component.
CELLS()
Returns the entire matrix (i.e., 2-dimensional array) of state objects for the CellMatrix.
  CELLS()[row][col] == CELL(row, col).
CELL_VALUE(row, col, comp)
CELL_VALUE(coords, comp)
comp is a String naming a Stock, Flow or Term in the cell capsule.
Returns: the current value of that component in the cell with the given coordinates.
  CELL VALUE(row, col, comp) == CELL(row, col)[comp]
RING(n)
WRING(n)
Returns: a list (array) of coordinate objects (i.e., containing row and col properties) for all cells comprising the square exactly n units away from the caller. (WRING is the “wrapped” version, which treats the surface as a torus).
WRAP(row, col)
WRAP(coords)
Performs a “wraparound” of the coordinates if they exceed the size of the matrix (or are negative).
WRAP(row, col) returns an array containing the new row and column;
WRAP(coords) returns a Coords object containing the new row and column.

Hexagonal Primops

The following should only be used if the CellMatrix is in hexagonal mode.

HEXRING(n)
Returns: a list (array) of coordinate objects (i.e., containing row and col properties) for all cells comprising the hexagon exactly n units away from the caller.
HEXBLOCK(n)
Returns: a list (array) of coordinate objects (i.e., containing row and col properties) comprising the hexagonal block of cells n units away from the caller or less.
HEXPATH(dir, dist)
Returns: a list of coordinates comprising the path of length dist in the direction indicated by dir. Directions are denoted by compass directions; i.e., “N”, “NE”, “SE”, “S”, “SW”, “NW”.

Convenience Primops

These primops perform useful functions that could otherwise be programmed.

CELLBLOCK(n)
CELLWBLOCK(n)
CELLRING(n)
CELLWRING(n)
Returns: a list of state objects for all cells in the ring or block (wrapped or otherwise) specified by n.
Available as of Nova 12.1.
COUNT_CELLS(l, comp, value)
l is a list of cell state objects, comp is a string naming a component in those cells (stock, term, flow, etc.), and value is any JavaScript data element.
Returns: Returns the number of objects in l for which the current value of comp is value.
Available as of Nova 12.1.
ALL_CELLS(l, comp, value)
NO_CELL(l, comp, value)
SOME_CELL(l, comp, value)
l is a list of cell state objects, comp is a string naming a component in those cells (stock, term, flow, etc.), and value is any JavaScript data element.
Returns: Respectively returns true if for all, none or some state objects in l the current value of comp is value; false otherwise.
Available as of Nova 12.1.

Agent Properties and Primops

The following may only be used by capsules contained in an AgentVector. id is an integer representing agent id of an agent. The term “caller” is used to identify the agent in which the primop is being executed, or the property value is being looked up.

Properties

birth
The point in model time at which the caller was created.
myId
The unique agent ID that has been assigned to the caller.
rows
cols
Bound to the total number of rows and columns in the space occupied by this AgentVector.
Super
The state object of the enclosing container.

Primops

AGE(id)
MYAGE()
Returns: the age (i.e., time since birth) of agent id, or of the caller, respectively.
AGENT(id)
Returns: the state object of the agent identified by id, if it exists.
AGENTS()
Returns: the list of live agent state objects.
AGENTS_AT(row, col)
AGENTS_AT(coords)
Returns: a list of agents contained in the cell at specified coordinates.
AGENT_COUNT()
Returns: the total number of agents.
AGENT_IDS()
Returns: the array of ids for currently living agents.
AGENT_VALUE(id, comp)
comp is a String naming a Stock, Flow or Term in the agent capsule.
Returns: the current value of that component in agent id.
  AGENT VALUE(id, comp) == AGENT(id)[comp]
CELL_COORDS(id)
Returns: a coords object containing the row/col coordinates of the current position of the agent identified by id. If id is omitted, returns the row/col coordinates of the caller.
CREATE([init], [n])
Schedules the creation of a n new agents (n is assumed to be 1 if omitted). init is an initializer object containing bindings for properties in the new agent. These may include init_x, init_ y and init_heading, to indicate the new agent’s initial position and direction. It may also include alternate initialization expressions for Stocks, Local Variables and Properties. If init is omitted, the new agent is a clone of the caller. All new agents are created at the end of the cycle.
CWRAP(row, col)
CWRAP(coords)
Identical to CellMatrix WRAP.
Available as of Nova 12.1.
KILL(id)
Schedules the elimination of agent id. All agent eliminations are carried out at the end of the cycle.
LOCATION(id)
Returns: the cartesian location of the agent identified by id in an object with properties x and y, and the current heading of the agent with property theta. If id is omitted, returns these data for the caller.
LWRAP(x, y)
LWRAP(loc)
Performs a “wraparound” of the location if either coordinate exceeds the size of the agent coordinate space (or is negative).
LWRAP(x, y) returns an array containing the new x and y;
LWRAP(loc) returns a location object containing the new coordinates as values of the properties x and y.
Available as of Nova 12.1
MOVE(x, y)
Sets the location of the caller to (x, y). All moves occur at the end of the cycle.
SET_HEADING(theta)
Sets the directional heading of the caller to theta (given in radians).

Convenience Primops

These primops perform useful functions that could otherwise be programmed.

COUNT_AGENTS(l, comp, value)
l is a list of agent state objects, comp is a string naming a component in those agents (stock, term, flow, etc.), and value is any JavaScript data element.
Returns: Returns the number of objects in l for which the current value of comp is value.
Available as of Nova 12.1.
ALL_AGENTS(l, comp, value)
NO_AGENT(l, comp, value)
SOME_AGENT(l, comp, value)
l is a list of agent state objects, comp is a string naming a component in those agents, and value is any JavaScript data element.
Returns: Respectively returns true if for all, none or some state object in l the current value of comp is value; false otherwise.
Available as of Nova 12.1.
RANDOM_MOVE(loc)
WRANDOM_MOVE(loc)
Returns: a location object (i.e., with fields x and y) representing a random move (non-wrapping and wrapping, respectively) of one unit from the location object loc. If loc is omitted it defaults to the location of the caller.
Available as of Nova 12.1.

SimWorld Primops

Cell and agent capsules in a SimWorld may respectively use the Cell and Agent properties and primops described above. Also in a SimWorld, cell capsules may call some agent primops and agent capsules may call some cell primops, as detailed below.

Cell Primops in a SimWorld

Cell capsules may call the following agent primops:

AGENT
AGENTS AT
AGENT_COUNT
AGENT_IDS
AGENT_VALUE
AGENTS
CREATE
KILL

Cell capsules in a SimWorld may call the following new primops:

MYAGENTS()
Returns: the list of agents currently contained in the caller.
MYAGENT_COUNT()
Returns: the number of agents currently contained in the caller.

Agent Primops in a SimWorld

Agent capsules may call the following cell primops:

CELL
CELLS
CELL_VALUE

Agent capsules in a SimWorld may call the following new primop:

MYCELL()
Returns: the state object of the cell containing the caller.

Hexagonal Agent Primop

The following should only be used by an agent if the cell component of the SimWorld is in hexagonal mode.

HEXMOVE(dist, dir)
Moves the calling agent distance dist in the direction dir. Directions are denoted by compass directions; i.e., “N”, “NE”, “SE”, “S”, “SW”, “NW”.

Convenience Primops

These primops perform useful functions that could otherwise be programmed.

AGENTBLOCK(n, ["sort"])
AGENTWBLOCK(n, ["sort"])
AGENTRING(n, ["sort"])
AGENTWRING(n, ["sort"])
Returns: a list of state objects for all agents in the ring or block (wrapped or otherwise) specified by n. If “sort” is included, the list is sorted in order of increasing distance from the caller.
Available as of Nova 12.1.

Node Properties and Primops

The following may only be used by capsules contained in a NodeNetwork. id is an integer representing node id of a node.

Properties

myId
Bound to the caller’s node id.
count
Bound to the number of nodes in the NodeNetwork.

Primops

CONNECTIONS_IN([id])
Returns: the array of connections into the node id (if id is omitted, it is assumed to be the caller). Each connection is an object with 3 properties: id, the node id of the source; strength, the raw strength of the connection; and n_strength, the normalized strength of the connection, where the total normalized strength of all connections into the caller is 1.
CONNECTIONS_OUT([id])
Returns: the array of connections from the node id (if id is omitted, it is assumed to be the caller). Each connection is an object with 3 properties: id, the node id of the target; strength, the raw strength of the connection; and n_strength, the normalized strength of the connection, where the total normalized strength of all connections from the caller is 1.
NODE(id)
Returns: a state object for node id.
NODE_COUNT()
Returns: the total number of nodes.
NODE VALUE(id, comp)
comp is a String naming a Stock, Flow or Term in the node capsule.
Returns: the current value of that component in node id.
 NODE VALUE(id, comp) == NODE(id)[comp]
NODES()
Returns: the array of node state objects.
INFLOW([id])
Returns: the total strength of connections into node id (if id is omitted, it is assumed to be the caller).
OUTFLOW([id])
Returns: the total strength of connections from node id (if id is omitted, it is assumed to be the caller).

NetWorld Primops

Cell and agent capsules in a NetWorld may respectively use the Node and Agent properties and primops described above. Also in a NetWorld, node capsules may call some agent primops and agent capsules may call some node primops, as detailed below.

Node Primops in a NodeWorld

Node capsules may call the following agent primops:

AGENT
AGENTS AT
AGENT_COUNT
AGENT_IDS
AGENT_VALUE
AGENTS
CREATE
KILL

Node capsules in a NetWorld may call the following new primops:

MYAGENTS()
Returns: the list of agents currently contained in the caller.
MYAGENT_COUNT()
Returns: the number of agents currently contained in the caller.

Agent Primops in a NetWorld

Agent capsules may call the following node primops:

NODE
NODES
NODE_VALUE

Agent capsules in a NetWorld may call the following new primops:

MYNODE()
Returns: the state object of the node containing the caller.
NETMOVE(nodeId)
Changes current location of caller to node indicated by nodeId. All moves occur at the end of the cycle.
NODE_NEIGHBORS(agentId)
Returns: a list of state objects corresponding to the the nodes to which the node currently occupied by agent agentId has outward links. If agentId is omitted, it is assumed to be the caller.