This is documentation for Mathematica 6, which was
based on an earlier version of the Wolfram Language.

Scan

 Scan[f, expr]evaluates f applied to each element of expr in turn. Scan[f, expr, levelspec]applies f to parts of expr specified by levelspec.
• Scan[f, expr] discards the results of applying f to the subexpressions in expr. Unlike Map, Scan does not build up a new expression to return.
• You can use Return to exit from Scan. Return[ret] causes the final value of Scan to be ret. If no explicit return values are specified, the final result from Scan is Null.
• Scan is useful in carrying out an operation on parts of expressions where the operation has a "side effect", such as making an assignment.
• Scan uses standard level specifications:
 n levels 1 through n Infinity levels 1 through Infinity {n} level n only {n1,n2} levels n1 through n2
• The default value for levelspec in Scan is {1}.
• A positive level n consists of all parts of expr specified by n indices.
• A negative level -n consists of all parts of expr with depth n.
• Level -1 consists of numbers, symbols and other objects that do not have subparts.
• Level 0 corresponds to the whole expression.
• With the option setting , Scan includes heads of expressions, and their parts. »
• Scan traverses the parts of expr in a depth-first order, with leaves visited before roots.
• If expr is a SparseArray object, Scan[f, expr] applies f only to the values or subarrays that explicitly appear in expr.
 Scope   (5)
 Options   (1)
 Applications   (2)