Procedures

Procedures are a kind of ``program''. When a procedure is called, the instructions in the body of the procedure are executed. A procedure is defined with the keyword to.

  to name_of_procedure :v1 :v2 :v3 .... [:v4 ....] [:v5 ....]
  Body of the procedure
  end

• name_of_procedure is the name given to the procedure.
• :v1 :v2 :v3 stand for the variables used internally in this procedure. (local variables).
• [:v4 ... ], [:v5 ...] are optional variables that we could add into the procedure (go below for more explanations).
• Body of the procedure represents the commands to be executed when this procedure is called.
  

Eg:

  to square :s
  repeat 4[fd :s rt 90]
  end

The procedure is called square and takes a parameter called s. square 100 will therefore produce a square, the length of whose sides is 100. (See the examples of procedures at the end of this manual.)

Since version 0.7c, it is possible to insert comments in the code preceded by #.

to square :s 
#this procedure allows a square to be drawn whose side equals :s. 
repeat 4[fd :s rt 90] # handy, isn't it? 
end