Copied from a comp.lang.lisp post by Ray Dillinger. Also see PPR:LispSchemeDifferences ,common-lisp.
What Common Lisp has got: What Scheme has got:
Much better developed standard SLIB + SRFI's + a hundred little
libraries libs that each do things differently
and aren't very standardized.
(Arguably Scheme is the place where new ideas fight for mindshare
and prove themselves - but the fights and the multiplicity
of contenders commits most code to one idea or another and
limits the code's interoperability, longevity, and/or
portability.)
A well-defined comprehensive A well-defined minimal spec plus
spec and several implementations dozens of variously comprehensive
which provide some extensions. implementations.
Escaping continuations only. Fully reentrant continuations.
Scheme just wins on this point.
(I have heard the arguments about whether fully reentrant
continuations are worth the cost of stack copying, or the
cost of heap-allocating and garbage collecting invocation
frames. I don't care. I'm just noting here that you can
do a *LOT* of things with them that are hard to do without
them.)
Lots of iterative constructs Memory-safe tail recursion avoids
the need for iteration syntax.
There's a looping construct, but
it's more complicated than tail
recursion so hardly anyone uses it.
If you care for them, you can
roll your own using continuations.
Both Lexically and Dynamically Lexical scope only, per the standard.
scoped special vars. Common Dynamically scoped vars are provided
Lisp just wins on this point. by some implementations as an extension
but code using them is not portable.
(I have heard the arguments about whether Dynamic scoping
is or is not a Bad Idea in the first place. I don't care.
I'm just noting that you can do things with it that you
can't easily do without it.)
C numeric types plus bignums Implementation-defined numeric types,
and complex nums, but no exact/ in some implementations failing to
inexact distinction. include bignums or complex nums. An
exact/inexact distinction is required
by the standard but properly implemented
in only about 3/4 of scheme systems.
In a good implementation, numerics
(capabilities and correctness) are
better than most CLs; on average,
they are worse.
Optional type declarations Optional type declarations provided
allow blazing fast numeric by a few implementations as extensions.
code to skip typechecking. Code using them is nonportable. Some
Common Lisp just wins on numeric implementations provide blazing speed
calculation speed. but generally at the expense of numeric
type richness and/or standard
conformance.
Signals and conditions, catch Roll your own using fully reentrant
and throw. continuations, or use any of several
libraries.
CLOS Roll your own objects using closures
and macros, or any of several OO
libraries. TinyCLOS and Meroon are
the most popular.
Well-defined standard module At least three competing well-defined
system. Common Lisp just wins module systems which it's a pain in
on this point. the butt to move modules between.
(or roll your own using scope, macros,
and/or preprocessing code).
Readtables for low-level Implementation-defined means of doing
macrology. Common Lisp wins low-level macrology - none of it
here. portable.
gensym tricks to avoid implicit hygienic macros with define-syntax and
variable captures in high-level syntax-case. You *can't* capture a
macros. variable in a macro except explicitly.
(Different people claim this as a "win" for both languages.
I don't care. There is little difference in what I can do
with it, nor in how hard it is to do it, so I'm not the guy
to judge a winner here.)
One-argument eval assumes environment specifier is second arg to
environment eval, allowing access to multiple
environments. Scheme just wins here.
Lambda syntax supports keyword Available as add-on library developed
arguments & default vals for using macros, but widely ignored.
optional arguments.
Symbols have properties, Variables have values and also names.
including but not limited to The names are lexically indistinguishable
function value and data value. from symbols but the value of a variable
is not a property of its name symbol.
Property lists are an extension
provided by relatively few schemes.
Native hash tables. Library hash tables.
Well-defined means of doing A fragile hack that depends on common
binary I/O. Common Lisp just character encodings and/or assumption
wins here. that character ports act as byte ports.
Assertions. Common Lisp just In scheme you have to do this as two
wins here. macros; one for development, that signals
an error if the condition isn't true, and
one for production code which "expands"
into nothing and gets out of the way.
The compiler will not use your assertions
to produce better code.
Large runtime environment Small runtime environment, easily
embeddable. Scheme wins here.