View source for Template:Calculator/Tutorial/Cyclic formulas

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Sometimes you might want the user to be able to enter in one of two fields, and have the other one update no matter which one they chose.

For example, in a unit converter, you might want them to be able to input into either unit.

You can accomplish this with a cyclic formula, where the two fields have formulas that depend on each other

e.g.

<syntaxhighlight lang="wikitext">
{{calculator
  |id=km
  |type=number
  |size=9
  |default=1.609344
  |formula=miles*1.609344
}} {{calculator label|label=km|for=km}} = 
{{calculator
  |id=miles
  |type=number
  |size=9
  |default=1
  |formula=km/1.609344
}} {{calculator label|label=miles|for=miles}}
</syntaxhighlight>

{{calculator
  |id=km
  |type=number
  |size=9
  |default=1.609344
  |formula=miles*1.609344
}} {{calculator label|label=km|for=km}} = 
{{calculator
  |id=miles
  |type=number
  |size=9
  |default=1
  |formula=km/1.609344
}} {{calculator label|label=miles|for=miles}}

Formulas that have a loop in them will stop propagating once they reach the original field that was edited. Thus if you have more than two fields as part of a cycle, you must ensure the path through the dependency graph of fields you want updated does not go through any node twice.

<!-- TODO explain this clearer, give example -->




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