ls:let

ls:let variable-name value

Creates a variable containing the given data that can be accessed by the child models.

ask turtles [
  ls:let my-color color
  ls:ask my-model [
    ask turtles [ set color my-color ]
  ]
]

ls:let works quite similar to let in that the variable is only locally accessible:

ask turtles [
  ls:let my-color color
]
;; my-color is innaccessible here

ls:let is very similar to let, except in a few cases.

• ls:let will overwrite previous values in the variable

If you do

ls:let my-var 5
ls:let my-var 6

my-var will be set equal to 6. There is no ls:set.

• ls:let supports variable shadowing

If you do

ls:let my-var 5
ask turtles [
  ls:let my-var 6
  ls:ask child-model [ show my-var ]
]
ls:ask child-model [ show my-var ]

child-model will show 6 and then 5. This is known as variable shadowing.

• The parent model cannot directly read the value of an ls variable

For example, this does not work.

ls:let my-var 5
show my-var

This is intentional. ls variables are meant to be used for sharing data with child models. The parent model already has access to the data.

Furthermore, changing the value of an ls let variable in a child model will not affect it in any other model. For example:

ls:let my-var 0
ls:ask ls:models [
  set my-var my-var + 1
  show my-var
]

All models will print 1.