On Wed, 23 Jan 2002, Keith Wansbrough wrote:
No, it was because they led to extremely confusing error messages. This was a particular concern because list comprehensions tend to be used a lot by beginners, in assignments designed to demonstrate the power and compactness of the language. If simple typos lead to error messages about functors and monads and other arcane and unknown concepts, these beginners are liable to be put off; if instead the error messages talk about lists then they will be much more useful.
Was it not possible to specialize the error message rather than the comprehensions? Alternatively, if the underlying type information really isn't available, why not give errors in terms of lists and have language sophisticates deal with the error message wierdness (they have to know that "list" in error messages really means monad). Or the implementation could simply have a beginner/advanced error message setting. I realize this is all water under the bridge, but personally, I would trade off more simple code for less readable error messages. -Alex- ___________________________________________________________________ S. Alexander Jacobson i2x Media 1-212-787-1914 voice 1-603-288-1280 fax