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added a clarification to the redex docs ala Carl's post on icfp-test

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svn: r17307
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Robby Findler 2009-12-15 16:41:55 +00:00
parent 3687048bbb
commit dd18cc837f
1 changed files with 5 additions and 4 deletions
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9
collects/redex/redex.scrbl
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@ -700,18 +700,19 @@ The fresh variables clause generates variables that do not
occur in the term being matched. If the @scheme[fresh-clause] is a occur in the term being matched. If the @scheme[fresh-clause] is a
variable, that variable is used both as a binding in the variable, that variable is used both as a binding in the
rhs-exp and as the prefix for the freshly generated rhs-exp and as the prefix for the freshly generated
variable. variable. (The variable does not have to be
a non-terminal in the language of the reduction relation.)
The second case of a @scheme[fresh-clause] is used when you want to The second case of a @scheme[fresh-clause] is used when you want to
generate a sequence of variables. In that case, the ellipses generate a sequence of variables. In that case, the ellipses
are literal ellipses; that is, you must actually write are literal ellipses; that is, you must actually write
ellipses in your rule. The variable var1 is like the ellipses in your rule. The variable @scheme[var1] is like the
variable in first case of a @scheme[fresh-clause], namely it is variable in first case of a @scheme[fresh-clause], namely it is
used to determine the prefix of the generated variables and used to determine the prefix of the generated variables and
it is bound in the right-hand side of the reduction rule, it is bound in the right-hand side of the reduction rule,
but unlike the single-variable fresh clause, it is bound to but unlike the single-variable fresh clause, it is bound to
a sequence of variables. The variable var2 is used to a sequence of variables. The variable @scheme[var2] is used to
determine the number of variables generated and var2 must be determine the number of variables generated and @scheme[var2] must be
bound by the left-hand side of the rule. bound by the left-hand side of the rule.
The side-conditions are expected to all hold, and have the The side-conditions are expected to all hold, and have the