Re: [Python-ideas] Statements vs Expressions... why?
On Thu, 2008-09-11 at 11:01 -0400, Mike Meyer wrote:
On Wed, 10 Sep 2008 14:54:44 -0700 Cliff Wells email@example.com wrote:
There were several design decisions to be made when designing Breve, the first and foremost being "will Breve templates be full-blown Python programs or will they be limited to expressions?". I chose the latter for a few reasons:
That seems to be a very poor decision. If you want Breve templates to play well with Python code (i.e. - be able to have Breve classes inherit from Python classes and vice versa - but I guess without statements, you don't have classes, so all of that is moot. Of course, not having classes seems like a bad idea as well.
Just to be clear because it appears to me you aren't quite following: Breve templates *are* Python code, or more exactly, they are a single Python expression. There is no preprocessor or interpreter that turns Breve into Python. It's just a bunch of class-magic.
The decision to be a single large expression is largely because this is a *template* engine and an expression maps most directly to XML because XML is structured similarly:
html [ head [ title [ 'A Brevé Template' ] ],
body [ h1 [ 'Briefly, Brevé' ], br, div ( style = 'text-align: center;' ) [ span [ ''' As you can see, Brevé maps very directly to the final HTML output. ''' ] ] ] ]
This is opposed to allowing the full of Python which would require a lot of syntax that is extraneous to the markup being generated (and most importantly would have caused a visual disjoint between the Breve source template and the final output).
Further, why do you feel that Breve templates - even if limited to expressions - need to be limited to what Python expressions can do?
Again, because Breve *is* Python. It's an internal DSL. Please see
for a definition of what that means. Another example of an internal DSL that's more widely used would be SQLAlchemy.