Purpose: Definition and discussion of set functionality, especially the function to check for membership of elements.
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::setops::contains set element

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2 Arguments:

   * The set to check, as a tcl-list, by value.
   * The text of the element to check for membership in the set.

Return value:

   * A number, in the set {0, 1}. 0 = element is no member of the set. 1 = element is a member of the set.

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Implementation:

 proc ::setops::contains {set element} {
    expr {[lsearch -exact $set $element] < 0 ? 0 : 1}
 }

   Speed:   O(n). n = Length of the list representing the set.

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C implementation using a hash table:

   Speed:   Basically O(1), O(n) in worst-case = transformation of a string or list into the hash-table representation.

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-- AK