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

# 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[e, tagi] with different tags are given in different lists. Reap[expr, patt]reaps only expressions sown with tags that match patt. Reap[expr, {patt1, patt2, ...}]puts expressions associated with each of the patti in a separate list. Reap[expr, patt, f]returns {expr, {f[tag1, {e11, e12, ...}], ...}}.
• 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[expr, _].
Evaluate a sequence of expressions, "reaping" ones that have been "sown":
 Out[1]=

Compute a sum, "reaping" i^2 "sown" at each step:
 Out[1]=
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