If you're using CMUCL and have to integrate with other people's C code (or your own), you might want to look at cparse
However, the poor soul obliged to program in C may benefit from: ILFIVE library.
For C++ damned souls, there's: Lily, LPP and InteLib libraries.
Pages in this topic: c-amplify CLiCC cparse SC Language
Also linked from: Bjarne Stroustrup C GNOME GPL Gtk s-exp syntax
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