[racket] disabling contracts again

Typed Racket's implementation uses conditional contracts internally.
There's a switch that determines, at syntax time, whether contracts
are added or not. This can completely eliminate the run time overhead
of contracts.

This cannot retroactively enable/disable contracts to compiled code; you
need to edit the file to flip the switch and then recompile Typed Racket.

The relevant code is in `collects/typed-racket/utils/utils'. Look for
`enable-contracts?', `provide/cond-contract', `define/cond-contract',
etc.

We've thought about packaging it up as a separate library, but since the
switch would have to belong to the library's client, we couldn't think
of a clean interface.

Vincent


At Fri, 18 May 2012 18:24:51 -0400,
Neil Van Dyke wrote:
> 
> Any new thoughts on adding a feature for disabling contracts?
> 
> In the past, I have been concerned about introducing contracts into 
> large performance-sensitive apps, since I didn't know the performance 
> impact.  I couldn't measure the performance impact without a large 
> amount of work that might have to then be thrown away.  The solution was 
> to simply not try using contracts.
> 
> I am newly interested in disabling contracts because my new code 
> documentation tool encourages the use of contracts, as well as 
> developing your modules as PLaneT packages.  However, as I am converting 
> all my PLaneT packages to use contracts, I fear this will make the 
> packages less useful to people who don't want the contract overhead.
> 
> Or, if no one is persuaded that this might be a good thing, perhaps 
> there's a submodules angle that makes implementing disable-able 
> contracts interesting to someone?  If so, it might also be relevant to 
> Typed Racket.
> 
> Neil V.
> 
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