parameterize in R7RS

[Marc Nieper-Wißkirchen]

The parameterize form in R7RS is, at best, underspecified if read favorably.

The R7RS reads: "The 〈param〉 and 〈value〉 expressions are evaluated in an unspecified order. The 〈body〉 is evaluated in a dynamic environment in which calls to the parameters return the results of passing the corresponding values to the conver-
sion procedure specified when the parameters were created. Then the previous values of the parameters are restored without passing them to the conversion procedure. The results of the last expression in the 〈body〉 are returned as the results of the entire parameterize expression."

Now, if I didn't know parameterize and the sample implementation of it in R7RS's appendix, this would lead me to assume that the conversion procedure is called everytime I invoke the reparameterized parameters.

This is certainly not what was meant.  It was certainly meant that the conversion procedure is once called per parameter in the dynamic environment of the parameterize expression.