“Tasks” in NetLogo 5.0beta1

“Tasks” in NetLogo 5.0beta1 March 21, 2011

What are tasks? chunks of code to be run once,run repeatedly, passed around, stored in variables, etc.

Known elsewhere as closures first-class functions lambda

Tasks in NetLogo 5.0 2 new data types 3 new primitives 8 primitives altered

2 new data types Command tasks Reporter tasks

3 new primitives task is-command-task? is-reporter-task?

6 altered primitives map, filter, reduce,n-values, sort-by foreach

2 more altered primitives run runresult

NOT altered (for now) ifelse, while, repeat, loop, ...

NOT altered (for now) ask, of, with, all?, ...

Backward compatible syntax square brackets inputs: ?1 (aka ?), ?2, ?3, ...

Implicit task syntax map [? * ?] [1 2 3] => [1 4 9] filter [? mod 2 = 0] [1 2 3 4] => [2 4] foreach sort turtles [ print ? ]

Explicit task syntax set next-task task [ fd 1 ] set coloring task [ ifelse-value (wealth > 100) [ red ] [ blue ] ]

Disambiguation of task type command or reporter?look at first token after the opening bracket (skipping left parens)

No tasks “escape” unless you use the explicit syntax

Running tasks run task [ print 5 ] => 5 print runresult task [5] => 5

Running tasks (variadic) let printer task [ print ?1 + ?2 ] (run print 2 3) => 5 let square task [? * ?] print (runresult square 5) => 25

Concise task syntax task die short for task [ die ] task fd short for task [ fd ? ] task + short for task [?1 + ?2]

Concise + implicit syntax map abs [1 -2 3 -4] => [1 2 3 4] reduce + [1 2 3 4] => 10 filter is-number? [1 “x” 3] => [1 3]

Extra inputs are ignored (runresult task [? * 2] 1 10 100)=> 2

Tasks are closures close over procedure inputs close over local variables

Closing over procedure inputs to-report printer [x] report task [ print x ] end run printer 5 => 5

Closing over local variables let x 5 let y task [ print x ] run y => 5

Close over bindings, not values let x 5 let y task [x] set x 10 print runresult y => 10

Current agent not closed over globals [g] ask turtle 0 [ set g task [ print who ] ] ask turtle 1 [ run g ] => 1

Nonlocal exits stop and report refer to dynamically enclosing procedure, not enclosing task(backwards compatible)

It’s fast 100x faster than compiling a string

Models using explicit tasks State Machine Example Termites 3D (afraid that’s all at the moment)

Use tasks, not strings! but, still need strings with run/runresult for running code entered by end user

Possible future work:named inputs [x => x * x] (or something like that?not sure yet)

Possible future work:complex reporter tasks task [ let x ... ... report ... ]

Wouldn’t it be cool if?:automatic updating set label task [energy] set color task [ ifelse-value (wealth < 100) [red] [blue] ]

Wouldn’t it be cool if?:scheduling in-ticks 5 task [ fd 1 ]

Questions? http://groups.yahoo.com/group/netlogo-users

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