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Condition Part (ConditionPart)

The more general form of table entries compared to IF-THEN-ELSE structures is mainly caused by the condition part:

As visible in the syntax diagram above, it consists not only of one but as many conditions as we want:

Furthermore there can also be assignments to variables:

Both kinds of units may be mixed up and put in any order. SCARLET will interprete them according to the rules given below:

 
• The boolean value of a condition part is given by the conjunction of its boolean expressions. If the result is TRUE, the devices in the consequence part will be executed; if it is FALSE, the consequence part will be ignored.
  
  

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  Example 47:
  
  

  Note that bool1 || bool2; bool3; and (bool1 || bool2) && bool3; are the same.

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• If ConditionPart has got no boolean expression at all, its boolean value is TRUE.
  
  
• The order in which the different units separated by semicolon appear in ConditionPart is also the order of their execution. Variables are updated immediately.
   

  Notice that SCARLET works nonstrictly, this means, as soon as the evaluation of one boolean expression leads to FALSE, SCARLET will skip the rest, because it is already sure that Consequence will be ignored.
  
  

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  Example 48:
  
  

  We give again a look at example 46. To calculate sum - instead of in the second entry - already in the first after center.state > 0; (as shown here), would lead to mistakes: In case that center.state == 0; is TRUE, center.state > 0; would be FALSE, so the evaluation of the first entry would be stopped immediately and sum would not be computed:

  
  center.state > 0; sum = left.state&1 + ... :
  
  state++; state%=3; :
  
  center.state == 0; sum >= 3; :
  
  SELF = {1}; :   
  

  ---

  
  
  

Hoping all these rules and conditions on the condition part become a bit clearer, we give a little view of what it is for. During the simulation, the table will be applied to each cell in order to update their states. As soon as a cell complies with the condition of a certain entry, its state changes according to the corresponding consequence part. Therefore, the state of a site can only be changed in Consequence, but not in the condition part. Once a site is updated, the rest of the table is no longer of interest to it: It can be skipped. (See also the algorithm.)
Besides, since the state usually depends on the states of the cell's neighbours, it is quite comfortable to just string the conditions on the neighbours in the condition part together.

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