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Cleaning causality in rejected alternative application

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I imagine a reader misunderstanding the causal relationship in the sentence as currently written. I hope for this to disambiguate. I believe this point in the document describes a design decision we the reader are presently considering. The reader should not imagine that an existing capacity to change `x` itself materially /prevents/ substitution---that we cannot substitute---the way a buoy's ability to float prevents it from sinking. I believe the writer means to say that the intended goal, supporting mutation, makes us (the author + the reader) reject direct substitution as an evaluation strategy.
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Jason Hemann 2021-05-29 14:53:58 -04:00 committed by Matthew Flatt
parent 46d3ea2bb8
commit 839b7f78f8
1 changed files with 3 additions and 3 deletions
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pkgs/racket-doc/scribblings/reference/eval-model.scrbl
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@ -386,9 +386,9 @@ an @tech{object}, so evaluating @racket[(f 7)] starts with a
Unlike in algebra, however, the @tech{value} associated with a procedure
argument variable can be changed in the body of a procedure by using
@racket[set!], as in the example @racket[(lambda (x) (begin (set! x 3)
x))]. Since the @tech{value} associated with argument variable @racket[x] can be
changed, the value cannot be substituted for @racket[x] when
the procedure is first applied.
x))]. Since the @tech{value} associated with argument variable @racket[x] should be
able to change, we cannot just substitute the value in for @racket[x] when
we first apply the procedure.
@margin-note{We do not use the term ``parameter variable'' to refer to
the argument variable names declared with a function. This choice avoids