clarify relation of CTFE correctness and const safety

diff --git a/ralf/_posts/2018-07-19-const.md b/ralf/_posts/2018-07-19-const.md
index 590763062154d9ead86e1f5afe76acba48c95fcd..23e9325ba43555e8b20de0e12f2b0f7783887fc7 100644 (file)
--- a/ralf/_posts/2018-07-19-const.md
+++ b/ralf/_posts/2018-07-19-const.md
@@ -138,7 +138,8 @@ So, we will likely have to live with either considering floating point operation
 I think it is possible to achieve CTFE correctness for all other operations, and I think we should strive to do so.
 
 Before we go on, notice that CTFE correctness as defined above does not say anything about the case where CTFE fails with an error, e.g. because of an unsupported operation.
 I think it is possible to achieve CTFE correctness for all other operations, and I think we should strive to do so.
 
 Before we go on, notice that CTFE correctness as defined above does not say anything about the case where CTFE fails with an error, e.g. because of an unsupported operation.

-That is a deliberate choice because it lets us gradually improve the operations supported by CTFE, but it is a choice that not everyone might agree with.
+CTFE would be trivially correct (in the above sense) if it just always immediately returned an error.
+However, since const-safe programs cannot error during CTFE, we know from CTFE correctness that *those* programs *do* in fact behave exactly the same at compile-time and at run-time.

 
 ## Unsafe Blocks in Const Context
 
 
 ## Unsafe Blocks in Const Context