### changeset 514:3b21f4395178

Fix a word that was only included in LaTeX version
author Adam Chlipala Thu, 26 Sep 2013 15:26:12 -0400 a4b3386ae140 ffe99c02fa18 src/GeneralRec.v 1 files changed, 1 insertions(+), 1 deletions(-) [+]
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--- a/src/GeneralRec.v	Thu Sep 19 17:28:32 2013 -0400
+++ b/src/GeneralRec.v	Thu Sep 26 15:26:12 2013 -0400
@@ -169,7 +169,7 @@
red; intro; eapply lengthOrder_wf'; eauto.
Defined.

-  (** Notice that we end these proofs with %\index{Vernacular commands!Defined}%[Defined], not [Qed].  Recall that [Defined] marks the theorems as %\emph{transparent}%, so that the details of their proofs may be used during program execution.  Why could such details possibly matter for computation?  It turns out that [Fix] satisfies the primitive recursion restriction by declaring itself as _recursive in the structure of [Acc] proofs_.  This is possible because [Acc] proofs follow a predictable inductive structure.  We must do work, as in the last theorem's proof, to establish that all elements of a type belong to [Acc], but the automatic unwinding of those proofs during recursion is straightforward.  If we ended the proof with [Qed], the proof details would be hidden from computation, in which case the unwinding process would get stuck.
+  (** Notice that we end these proofs with %\index{Vernacular commands!Defined}%[Defined], not [Qed].  Recall that [Defined] marks the theorems as %\emph{%#<i>#transparent#</i>#%}%, so that the details of their proofs may be used during program execution.  Why could such details possibly matter for computation?  It turns out that [Fix] satisfies the primitive recursion restriction by declaring itself as _recursive in the structure of [Acc] proofs_.  This is possible because [Acc] proofs follow a predictable inductive structure.  We must do work, as in the last theorem's proof, to establish that all elements of a type belong to [Acc], but the automatic unwinding of those proofs during recursion is straightforward.  If we ended the proof with [Qed], the proof details would be hidden from computation, in which case the unwinding process would get stuck.

To justify our two recursive [mergeSort] calls, we will also need to prove that [split] respects the [lengthOrder] relation.  These proofs, too, must be kept transparent, to avoid stuckness of [Fix] evaluation.  We use the syntax [@foo] to reference identifier [foo] with its implicit argument behavior turned off.  (The proof details below use Ltac features not introduced yet, and they are safe to skip for now.) *)