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Re: learning languages [Was: Re: Y Store now C++]

Sundar Narasimhan wrote:

> Why are languages viewed as all or nothing deals.. why don't they have
> a gradual light-dark setting (to (ab)use Dan's Toaster analogy) that
> could help people learn them. Are people thinking about changing the
> "interface" such programming language work-products present to the
> target market?

DrScheme is a step in this direction.  We recognized that textbooks do
not present languages as all-or-nothing deals, so why should
programming languages?  We therefore built a series of language
"levels" that grow semantically more complex.  In the more restrictive
language levels, the environment can place certain restrictions that
catch errors sooner.  (For instance, in a language level without
first-class functions, certain syntactic patterns that would be
syntactically legal but lead to erroneous programs in full Scheme can
be rejected statically.)

Many of the institutions that use DrScheme employ language levels; a
few are, however, too proud to do so.