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New Mexico Computer Science For All

New Mexico Computer Science For All. Local Variables in Netlogo Maureen Psaila-Dombrowski. Variables in Computer Science. A variable is a container that holds a value It has the following fixed properties A name, used in the program to access the value.

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New Mexico Computer Science For All

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  1. New Mexico Computer Science For All Local Variables in Netlogo Maureen Psaila-Dombrowski

  2. Variables in Computer Science • A variable is a container that holds a value • It has the following fixed properties • A name, used in the program to access the value. • A type (number, text, boolean, etc.) • A physical location in memory • The value stored in the variable can be used and changed as the program is executed

  3. Steps for Using Variables • Three Steps for Using Variables • Declare – allocates the space for the variable and sets the name given to the variable • Initialize – set the initial value of the variable • Call/Modify – Use it in the program or change the value stored in the variable as the program is executed

  4. Local Variables • A local variable is a variable that can only be used in the procedure or command block where it is declared. • Cannot be accessed by the program in other locations

  5. Local Variables in NetLogo • Declare and initialize local variables using the let command example: let newvar 15 • Declares a variable named newvar and initializes to 15

  6. Local Variables in NetLogo • Call a local variable example: set color newvar • Sets the color of the turtle to color 15 (red) • Modify a local variable using the set command example: set newvar 25 • Modifies the value of newvar to 25

  7. NetLogo Example: Distance from (0,0) • Setup Procedure • Clears the NetLogo world, creates 50 turtle, scatters them and colors them red • Set the color of turtle #1 to white

  8. NetLogo Example: Distance from (0,0) • Walk Procedure • Declares and initializes the variable “dist” • Moves all turtles forward 1 step • Modifies the value of “dist” to be the distance of turtle #1 from the origin • Prints

  9. NetLogo Example: Distance from (0,0) • Walk Procedure • Declares and initializes the variable “dist” • Moves all turtles forward 1 step • Modifies the value of “dist” to be the distance of turtle #1 from the origin • Prints

  10. NetLogo Example: Distance from (0,0)

  11. Summary • A variable is a named memory location • Holds a value • Value can used and/or changed as the program is executed • Three steps for using variables • Declare • Initialize • Call/Modify • A Local Variable used locally in the program where it is declared (procedure or command block)

  12. Further Information • If you would like more information: • NetLogo Manual • NetLogo Dictionary

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