Syntax: | flat_sequence(s)
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Description: | Returns TRUE (1) if, and only if, s is a sequence that contains only atoms. |
Syntax: | non_empty(s)
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Description: | Returns TRUE (1) if, and only if, s is a sequence that is not empty. |
Syntax: | pair(s)
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Description: | Returns TRUE (1) if, and only if, s is a sequence that contains only two elements. |