BUILT-IN MATHEMATICA SYMBOL

Scan

evaluates f applied to each element of expr in turn.

applies f to parts of expr specified by levelspec.

Scan 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.

Level consists of numbers, symbols, and other objects that do not have subparts.

With the option setting Heads->True, 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 applies f only to the values or subarrays that explicitly appear in expr.

Scan level 1 (default):

Scan down to level 2:

Scan only level 2:

Scan levels 0 through 2:

Scan down to level 3:

Scan all levels, starting at level 1:

Scan also level 0:

Negative levels:

Positive and negative levels can be mixed:

Different heads at each level:

Scan can be used on expressions with any head:

Throw works inside Scan:

By default, heads are not scanned:

Make assignments based on data:

Find all leaves in an expression:

Leaves are visited before roots:

Scan does the same as Map, but without returning a result:

Use Sow and Reap to collect results: