- All expressions are numeric with units.
- Any quantity is converted into a coherent derived units of the SI (International System of Units), for example, a length will be converted into meters, a weight into kilograms.
| name | syntax | description |
|---|---|---|
| decimal | decimal | decimal number with or without a sign and a decimal point |
| π | π pi |
the ratio of a circle's circumference to its diameter, approximately equal to 3.14159 |
| name | syntax | description |
|---|---|---|
| numeric with unit | numeric [unit] |
numeric as a quantity with the specified unit |
| numeric without unit | numeric numeric [] |
numeric without a unit or with a dimensionless unit |
| name | syntax | description |
|---|---|---|
| en-unit conversion | expr[unit] |
the dimensionless value _expr_ makes a quantity with the given unit,e.g. (100+200)[m] is equivalent to 300[m] |
| de-unit conversion | (unit) expr |
the quantity unit is converted to a number in the given unit, e.g. (m)(1 [km]) is equivalent to 1000.0 |
Various variables can be read in a task definition. Most variables except utility variables can be either the current value, the increment since the last time step, or the derivative value.
Simple references can be used in any agent.
Utility variables are those defined in the where clause of a task.
Because they are temporary storage to perform the task, you can refer only to its current value.
The time represents the duration since the start of the simulation.
The increment of the time variable is naturally the time step of the simulation.
| name | syntax | description |
|---|---|---|
| utility variable | identifier | the value of the variable defined in the where clause in the task |
| time | time |
the current time |
| time step | Δtime delta time |
the time step of the simulation |
The attributes of the performer of the task can be accessed in the following ways. The performer can be either the world, a patch, or an animat.
| name | syntax | description |
|---|---|---|
| my attribute | my identifier |
the value of the individual's attribute |
| my incremental attribute | my Δ attribute my delta attribute |
the increment of the individual's attribute |
| my differential attribute | my d/dt attribute |
the derivative of the individual's attribute |
Patch attributes can be used in the tasks of located agents, namely animats and patches.
| name | syntax | description |
|---|---|---|
| spatial attribute | here's attribute |
the value of the patch's attribute where the individual is located |
| spatial incremental attribute | here's Δ attribute here's delta attribute |
the increment of the patch's attribute where the individual is located |
| spatial differential attribute | here's d/dt attribute |
the derivative of the patch's attribute where the individual is located |
Any task definition can refer to the value of an attribute of the World agent.
| name | syntax | description |
|---|---|---|
| global attribute | world's attribute |
the value of the world global attribute |
| global incremental attribute | world's Δ attribute |
the increment of the world global attribute |
| global differential attribute | world's d/dt attribute |
the derivative of the world global attribute |
Tasks that defines an interaction between two animats takes a peer animat, which is called object.
For example, a task that a wolf eat a goat, goat is the object in the task.
The attributes of the object can be accessed in the following ways.
| name | syntax | description |
|---|---|---|
| object attribute | object's attribute |
the value of the object's attribute specified as the object of the task |
| object incremental attribute | object's Δ attribute object 's delta attribute |
the increment of the object's attribute specified as the object of the task |
| object differential attribute | object's d/dt attribute |
the derivative of the object's attribute specified as the object of the task |
| name | syntax | description |
|---|---|---|
| direction of agent | direction agent |
the direction of the agent from the individual |
| distance to agent | distance agent |
the distance between the individual and the agent |
| direction of spatial gradient | direction neighbor's attribute |
the direction of the gradient of attribute at the current patch |
| length of a patch | length of here |
the length of the current patch |
| area of a patch | area of here |
the area of the current patch |
| name | syntax | description |
|---|---|---|
| number of agents in radius | number of agent in expression radius |
the number of individual agents in the given radius |
| number of local agents | number of agent here |
the number of individual agents in the same patch |
| number of agents | number of agent in world |
the number of individual agents in the simulation |
| density of agents in radius | number of agent in expression radius |
the number of individual agents per area in the given radius |
| density of local agents | density of agent here |
the number of individual agents per area in the patch |
| density of agents | density of agent in world |
the number of individual agents per area in the simulation |
| name | syntax | description |
|---|---|---|
| parenthesis | ( expr ) |
the value of the expr |
| negation | - expr |
flips the sign of the value |
| addition | expr1 + expr2 |
sums the two values |
| subtraction | expr1 - expr2 |
diffs the two values |
| product | expr1 * expr2 |
multiplies the two values |
| fraction | expr1 / expr2 |
the left-value over the right-value |
| remainder | expr1 % expr2 |
the remainder of the left-value by the right-value |
| repeated multiplication | expr ^ digit |
expr powered to digit |
| square root | sqrt(expr) |
the square root of expr which must be non-negative |
| power | power(expr1, expr2) |
the left value powered to the right value expr1 and expr2 must be non-dimensional |
| exponential | exp(expr) |
e powered to expr the expr must be non-dimensional |
| natural logarithm | ln(expr) |
the x such that e powered to x equals to expr the expr must be non-dimensional |
| sine | sin(expr) |
the sine of expr the expr must be an angle, such as radians and degrees |
| cosine | cos(expr) |
the cosine of expr where the expr must be an angle the expr must be an angle, such as radians and degrees |
| absolute value | abs(expr) |
the value without the sign |
| positive | positive(expr) |
the value if positive, otherwise 0 |
| round | round(expr) |
the rounded value |
| floor | floor(expr) |
the rounded-down value |
| ceiling | ceiling(expr) |
the rounded-up value |
| maximum | max(expr1, expr2, ..., exprn) |
the most value among arguments all expr must have the same dimension |
| minimum | min(expr1, expr2, ..., exprn) |
the least value among arguments all expr must have the same dimension |
| average(mean) | mean(expr1, expr2, ..., exprn) |
the mean value of arguments all expr must have the same dimension |
| name | syntax | description |
|---|---|---|
| uniform distribution | uniform expr1 to expr2 |
a random number from the uniform distribtion in [expr1, expr2] expr1 and expr2 must have the same dimension |
| uniform integer distribution | uniform_integer expr1 to expr2 |
a random integer from the uniform distribtion in [expr1, expr2] expr1 and expr2 must have the same dimension |
| normal distribution | normal expr1 sigma expr2 |
a random number from the normal distribtion with the mean=expr1 and sigma=expr2 expr1 and expr2 must have the same dimension |
| gamma distribution | gamma expr1 scale expr2 |
a random number from the gamma distribution with the shape=expr1 and scale=expr2 expr2 must be non-dimensional |
| log-logistic (or Fisk) distribution | loglogistic expr1 shape expr2 fisk expr1 shape expr2 |
a random number from the log-logistic distribution with the scale=expr1 and shape=expr2 expr2 must be non-dimensional |