!! +var+ +exec+ +string+
tit:product
type:$type_both
alias:prod, multiply
syntax:!product ``fn'' for ``v''=``v1'' to ``v2'' [step ``st'']\
$ !product ``fn'' for ``v'' in ``v1,v2,v3,...''
mean:Computes the product of a function ``fn(v)'' with variable ``v'' replaced \
  successively by values ``v1'', ..., ``v2''. <p>\
  In the second syntax, the values are given with respect to each item in the list ``v1,v2,...''.\
  </p>
