@@ -325,6 +325,22 @@ traversal][traversal] that performs the following steps for each node _N_: |
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2. **R**: traverse [_tail_][term-tail] |
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3. **N**: visit _N_ itself |
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+###### Enter |
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+ |
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+**Enter** is a step right before other steps performed on a given node _N_ when |
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+[**traversing**][traversal] a tree. |
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+ |
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+For example, when performing _preorder_ traversal, **enter** is the first step |
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+taken, right before visiting _N_ itself. |
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+ |
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+###### Exit |
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+ |
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+**Exit** is a step right after other steps performed on a given node _N_ when |
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+[**traversing**][traversal] a tree. |
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+ |
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+For example, when performing _preorder_ traversal, **exit** is the last step |
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+taken, right after traversing the [_tail_][term-tail] of _N_. |
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+ |
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## Tree traversal |
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**Tree traversal** is a common task when working with a [_tree_][term-tree] to |