Re: Object-relational impedence
Date: Mon, 10 Mar 2008 13:30:40 +0100 (CET)
Marshall <marshall.spight_at_gmail.com> wrote in news:95abb6fb-e5e1-4604-b0f9-9fe3d5bcfadc_at_e10g2000prf.googlegroups.com:
>> Marshall <marshall.spi..._at_gmail.com> wrote in >> news:b5ab6022-5cea-45a1- >> >> Superficially, you can perform the translation, but the assignment >> required to imitate the projection makes any such language not >> referentially transparent. You may consider the non-transparency a >> non- issue of course.
> Um, how so? I'm not sure I see what you mean.
"A language that supports the concept that ``equals can be substituted for equals'' in an expresssion without changing the value of the expression is said to be referentially transparent. Referential transparency is violated when we include set! in our computer language. This makes it tricky to determine when we can simplify expressions by substituting equivalent expressions. Consequently, reasoning about programs that use assignment becomes drastically more difficult."
http://mitpress.mit.edu/sicp/full-text/sicp/book/node54.html Received on Mon Mar 10 2008 - 13:30:40 CET