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From: gudeman@cs.arizona.edu (David Gudeman)
Newsgroups: comp.lang.misc
Subject: Re: Answers, Chapter 1: TeX
Message-ID: <27209@megaron.cs.arizona.edu>
Date: 6 Nov 90 21:28:12 GMT
Organization: U of Arizona CS Dept, Tucson
Lines: 38

In article  <5077@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
] The compiler must
]provide sufficient information to tell the loader which constraints
]must be promoted across the call-tree - but this information can
]exist in a language independent form.

Sounds like a fun new software tool -- a conditional linker.  I wish I
had time to work on it.  I visualize a linker with control constructs
roughly similar to the C preprocessor.  One necessary exension of
course, would be an error producer

#error "Declaration of function %s does not match definition" f1

I expect that it would also need some extra things in the expression
syntax for type checking and such, for example

#if type(X) = type(Y)

where X and Y are some sort of (language-independent) type expression.

It could be used to conditionaly compile code depending on things that
can't be determined until link time like

#if guaranteed_not_aliased(A,B)
/* highly optimized code that assumes no aliasing */
#else
/* less optimized code to do the same thing for the case where A and B
might be aliased */
#endif

Furthermore, this linker could be downward compatible with linkers
that don't have conditional statements, so that you could install the
new linker without changing the existing compilers on your system.
-- 
					David Gudeman
Department of Computer Science
The University of Arizona        gudeman@cs.arizona.edu
Tucson, AZ 85721                 noao!arizona!gudeman