• Heads is an option for functions which use level specifications that specifies whether heads of expressions should be included.
• Heads -> True treats heads just like other elements of expressions for the purpose of levels.
• Heads -> False never includes heads as part of any level of an expression.
• Most functions which use level specifications have the default setting Heads -> False
. One exception is Position
, for which the default is Heads -> True
• New in Version 2.