macros

What makes Lisp macros so special?

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To give the short answer, macros are used for defining language syntax extensions to Common Lisp or Domain Specific Languages (DSLs). These languages are embedded right into the existing Lisp code. Now, the DSLs can have syntax similar to Lisp (like Peter Norvig’s Prolog Interpreter for Common Lisp) or completely different (e.g. Infix Notation Math … Read more

What is “:-!!” in C code?

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This is, in effect, a way to check whether the expression e can be evaluated to be 0, and if not, to fail the build. The macro is somewhat misnamed; it should be something more like BUILD_BUG_OR_ZERO, rather than …ON_ZERO. (There have been occasional discussions about whether this is a confusing name.) You should read … Read more

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