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Formula Syntax

Definition: Visual AgenTalk (VAT) Formula Syntax is used to create VAT formulas. The following Formula Syntax is accepted by Ristretto :

Operation
Definition Example Result
Arithmetic Operations x + y
x - y
x * y
x / y
Basic arithmetic operations 3 + 4 7
Agent Attribute Access attribute Access the value of an agent attribute. An agent can have any number of attributes defined by the user Diameter

Diameter * 3.14
value of the agent attribute "Diameter"

value of attribute "Diameter" multiplied by 3.14
Remote Agent Attribute Access attribute[up]
attribute[down]
attribute[left]
attribute[right]
attribute[top]
attribute[bottom]
attribute[bottom]
attribute[row, col]

attribute[stacked_above]
attribute[stacked_below]
Access the value of other agents' attribute using relative coordinates.

Valid coordinates are up, down, left, right, top and bottom. Coordinates can also be specified numerically as row, column. Valid values for row and column are -1, 0, 1. Positive row values indicates right, positive column indicates down.

You may also use attribute[stacked_above]
to access the value of attribute in the agent that is stacked directly above and attribute[stacked_below]
to access the value of attribute in the agent that is stacked directly below.
age[left]


age[top]


Temperature[-1,-1]



0.25 * (Temp[left] + Temp[right]+ Temp[up] + Temp[down])

height[stacked_above]
value of the "Age" attribute of agent to the left

value of the "Age" attribute of the agent on top

value of the "Temperature" attribute of the agent above to the left

The average of the value of the "Temp" attribute of the agents left, right, up and down.

value of the "height" attribute of the agent stacked directly above
Simulation Property Access @simproperty Access the value of a global simulation property

Simulation Properties are used to share information between agents. Users can inspect and edit the values of simulation properties using the simulation property editor. The "@" sign is used to differentiate the simulation properties from agent attributes.
@Time value of simulation property "Time"
Agent Query Functions agents_with_depiction(depiction_name) Query function that returns the number of agents with a given depiction. agents_with_depiction(dead_frog) returns the number of agents that have a depiction with the name "dead_frog" in the simulation.
agents_of_type(agent_name) Query function that returns the number of agents with a given name. agents_with_name(frog) returns the number of "frog" agents in the simulation.
Trigonometric Functions sin(x) Trigonometric function sine, where x is expressed in radians sin(3) 0.1411
cos(x) Trigonometric function cosine, where x is expressed in radians cos(3) -0.9900
tan(x) Trigonometric function tangent, where x is expressed in radians tan(3) -0.1425
Random Number Generator random(number) Returns a pseudo random number between zero and number .

AgentSheets differentiates between integers and decimal numbers. If the number is an integer (e.g. 4), an integer between 0 and number is returned, whereas if number is a decimal number, a decimal number between 0 and number is returned.
random(4.0)


random(4)
returns decimal number between 0 (inclusive) and 4.0 (exclusive)

returns either 0.0, 1.0, 2.0, or 3.0
Other x ^^ y Exponentiation function. Raises the base number x to the exponent y 15^^4 50625
sqrt(x) Square root function. Takes the square root of number x, where x is a non-negative integer or a decimal number (x>=0). sqrt(256) 16
x % y Modulo function. Gives the remainder of the division of x / y. 17 % 4 1

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