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| |
| _Cycles_ |
| |
| # Reference cycles |
| |
| CUE can handle many types of cycles just fine. |
| Because all values are final, a field with a concrete value of, say `200`, |
| can only be valid if it is that value. |
| So if it is unified with another expression, we can delay the evaluation of |
| this until later. |
| |
| By postponing that evaluation, we can often break cycles. |
| This is very useful for template writers that may not know what fields |
| a user will want to fill out. |
| |
| |
| <!-- CUE editor --> |
| _cycle.cue:_ |
| ``` |
| // CUE knows how to resolve the following: |
| x: 200 |
| x: y + 100 |
| y: x - 100 |
| |
| // If a cycle is not broken, CUE will just report it. |
| a: b + 100 |
| b: a - 100 |
| ``` |
| |
| <!-- result --> |
| `$ cue eval -i -c cycle.cue` |
| ``` |
| x: 200 |
| y: 100 |
| a: _|_ /* cycle detected */ |
| b: _|_ /* cycle detected */ |
| ``` |
