BUILT-IN MATHEMATICA SYMBOL

Reap

Reap[expr]
gives the value of expr together with all expressions to which Sow has been applied during its evaluation. Expressions sown using Sow[e] or Sow

with different tags are given in different lists.

Reap

reaps only expressions sown with tags that match patt.

Reap

puts expressions associated with each of the

in a separate list.

Reap

returns

.

MORE INFORMATION

Sow and Reap provide a convenient way to accumulate a list of intermediate results in a computation.

Reap accumulates expressions in the order in which Sow is applied to them.

Expressions sown with a particular tag are collected by the innermost Reap whose pattern matches the tag.

Reap[expr] is equivalent to Reap.

Reap has attribute HoldFirst.

EXAMPLES

CLOSE ALL

Basic Examples (2)

Evaluate a sequence of expressions, "reaping" ones that have been "sown":

Compute a sum, "reaping"

"sown" at each step:

Evaluate a sequence of expressions, "reaping" ones that have been "sown":

In[1]:=

Out[1]=

Compute a sum, "reaping"

"sown" at each step:

In[1]:=

Out[1]=

Scope (2)

Make a separate sublist for each tag being reaped:

Count the number of instances of each integer separating the negative:

Generalizations & Extensions (1)

Apply

to each distinct tag and list of values:

Applications (3)

Find the unique elements in a list, in the order they first occur (unsorted union):

Find the list of values sampled by Plot:

Remove duplicates from a list, keeping original order:

This is like Union without the sorting:

Properties & Relations (3)

If no expressions are sown, Reap returns an empty list of expressions it has reaped:

Reap collects expressions in exactly the order they are sown:

The list associated with the first tag to be encountered is given first: