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What are Common Lisp macros?
The Common Lisp macro facility allows the user to define arbitrary functions that convert certain Lisp forms into different forms before evaluating or compiling them. This is done at the expression level, not at the character-string level as in most other languages.
How are macros defined in LISP?
Defining a Macro In LISP, a named macro is defined using another macro named defmacro. Syntax for defining a macro is − (defmacro macro-name (parameter-list)) “Optional documentation string.” body-form.
What does Setf do in Lisp?
setf is actually a macro that examines an access form and produces a call to the corresponding update function. Given the existence of setf in Common Lisp, it is not necessary to have setq, rplaca, and set; they are redundant. They are retained in Common Lisp because of their historical importance in Lisp.
Is Common Lisp fast?
At 25000 values, Common Lisp is almost 1.8 times as fast as the C version, and the compilation time is 65% of the total evaluation time. In Figure 2, for programs of depth 8, Common Lisp passes C at between 5000 and 6000 values, and the compilation time is 16.2 seconds.
What is SETQ in LISP?
(setq var1 form1 var2 form2 …) is the simple variable assignment statement of Lisp. First form1 is evaluated and the result is stored in the variable var1, then form2 is evaluated and the result stored in var2, and so forth. setq may be used for assignment of both lexical and dynamic variables.
Is a macro not a function?
Macros are typically faster than functions as they don’t involve actual function call overhead….Conclusion:
| Macro | Function |
|---|---|
| Macro is Preprocessed | Function is Compiled |
| No Type Checking is done in Macro | Type Checking is Done in Function |
What is Progn LISP?
The general purpose special operator progn is used for evaluating zero or more forms. The value of the last form is returned. For instance, in the following, (print ‘hello) is evaluated (and its result is ignored), and then 42 is evaluated and its result (42) is returned: (progn (print ‘hello) 42) ;=> 42.
What is let in Lisp?
The let expression is a special form in Lisp that you will need to use in most function definitions. let is used to attach or bind a symbol to a value in such a way that the Lisp interpreter will not confuse the variable with a variable of the same name that is not part of the function.
What is SETQ in Lisp?
Is Common Lisp faster than C++?
Contrary to popular belief, Lisp code can be very ef- ficient today: it can run as fast as equivalent C code or even faster in some cases. language, there are very good and effi- cient compilers out there, that can deliver not only byte-code, but also native machine code from Lisp source.
What does cons do in Lisp?
cons constructs memory objects which hold two values or pointers to values. These objects are referred to as (cons) cells, conses, non-atomic s-expressions (“NATSes”), or (cons) pairs. In Lisp jargon, the expression “to cons x onto y” means to construct a new object with (cons x y) .
Where do you find the word macro in Lisp?
You’d better read it on the Cookbook: https://lispcookbook.github.io/cl-cookbook/macros.html The word macro is used generally in computer science to mean a syntactic extension to a programming language. (Note: The name comes from the word “macro-instruction,” which was a useful feature of many second-generation assembly languages.
How to call macroexpand with slime in Lisp?
Note: with Slime, you can call macroexpand by putting the cursor at the left of the parenthesis of the s-expr to expand and call the function M-x slime-macroexpand- [1,all], or C-c M-m: Our macro is very close to the following function definition:
Which is the shortcut for quote in Lisp?
In Lisp, because code is represented as lists, we can simply return a list that represents code. We also use the quote: each quoted symbol evaluates to itself, aka it is returned as is: the quote character, ‘, is a shortcut for quote, a special operator (not a function nor a macro, but one of a few special operators forming the core of Lisp).