2006-08-09 11:55:00 2006-08-17 14:14:17.044484 False True 2006-08-09 11:58:00 - If a list is quoted, evaluation returns the list itself; if it is not quoted, the list is treated as code, and evaluation returns its value. - > (list '(+ 2 1) (+ 2 1)) - ((+ 2 1) 3) What is a list? 2006-08-17 02:02:11.278895 A list can be either a program or data. E.g.: - () - (()) - ((())) - ((a b c)) - ((1 2) 3 4) - (mouse (monitor 512 342) (keyboard US)) - (defun factorial (x) (if (eql x 0) 1 (* x (factorial (- x 1))))) 2006-08-17 01:43:16.108773 * @comport funny%stuff 9^ case-2 What is an atom? 2006-08-17 02:02:11.287606 - A number or a symbol. - Any sequence of letters, digits, and punctuation characters is an atom if it is preceded and followed by a blank space (this includes the beginning or end of a line) or a parenthesis. 2006-08-17 01:43:16.116772 What is a symbol? 2006-08-17 02:02:11.295456 - A symbol is essentially a unique named item (it is identical to any other symbol spelled the same way), - written as an alphanumeric string in source code, - used either as a variable name or as a data item in symbolic processing - it doesn't matter whether you use uppercase or lowercase letters in your symbol names - a symbol can have a value as a function and a variable (and documentation, property list, and print name) at the same time 2006-08-17 01:43:16.120406 What is a form? 2006-08-17 02:02:11.303924 A form can be either an atom or a list. The important thing is that the form is meant to be evaluated. 2006-08-17 01:43:16.124685 How does evaluation of a form work? 2006-08-17 02:02:11.311861 - If the form is an atom, Lisp treats the atom as a name, and retrieves the value for the name (if a value exists). - If the form is a list, then the first element must be either a symbol or a special form called a lambda expression. It is applied to the remaining elements. - There are two kinds of forms that don't evaluate all of their arguments: special forms and macros. 2006-08-17 01:43:16.128910 What do (atom 123) and (numberp 123) do? 2006-08-17 02:02:11.319712 - ATOM and NUMBERP are predicates. - Predicates return a true or false value. - ATOM returns T if its one argument is a Lisp atom. - NUMBERP returns T if its argument is a number. 2006-08-17 01:43:16.133123 The right way to return multiple values from a function is ... 2006-08-17 02:02:11.327600 ... to use the VALUES form. -? (values 1 2 3 :hi "Hello") -> 1 -> 2 -> 3 -> :HI -> "Hello" VALUES is a function, and so evaluates its arguments. 2006-08-17 01:43:16.137495 SETQ 2006-08-17 02:02:11.335431 - Sets the value of a variable, e.g. (setq my-name "David") - SETQ's first argument is a symbol. This is not evaluated. - The second argument is assigned as the variable's value. - SETQ returns the value of its last argument. 2006-08-17 01:43:16.141705 -? (setq var-1 'var-2) -> VAR-2 -? var-1 -> VAR-2 -? var-2 ->| Error: Unbound variable -? (set var-1 99) -> 99 SET 2006-08-17 02:02:11.343280 - Similar to SETQ but the first argument gets evaluated. - Assigns a value to the symbol that is the value of the first argument. 2006-08-17 01:43:16.145914 ? (let ((a 3) (b 4) (c 5)) (* (+ a b) c)) => 35 LET 2006-08-17 02:02:11.351108 - In general, LET looks like this: (let (bindings) forms) - where bindings is any number of two-element lists -- each list containing a symbol and a value -- and forms is any number of Lisp forms. - The forms are evaluated, in order, using the values established by the bindings. - LET returns the value(s) returned by the last form. 2006-08-17 02:01:46.102947 IF 2006-08-17 02:02:11.359084 Takes three arguments: a test expression, a then expression, and an else expression. 2006-08-17 01:43:16.150131 COND 2006-08-17 02:02:11.366937 - The COND macro lets you evaluate Lisp forms conditionally. - (cond ((conditition1) value1) ((condition2) value2)) - The clauses are selected in order -- as soon as one test succeeds, the corresponding body forms are evaluated and the value of the last body form becomes the value of the COND form. - Conventional use of COND uses T as the test form in the final clause ("else"). 2006-08-17 01:43:16.154366 EQL 2006-08-17 02:02:11.374794 - EQL returns T if its two arguments are identical (or the same number), otherwise NIL. - (eql a b) 2006-08-17 01:43:16.158584 QUOTE 2006-08-17 02:02:11.382657 - Suppresses Lisp's normal evaluation rules. - Useful when we'd like a symbol to stand for itself, rather than its value. - (SETQ A B) vs. (SETQ A (QUOTE B)) - Shorthand: 'form ≡ (QUOTE form) 2006-08-17 01:43:16.163062 CONS 2006-08-17 02:02:11.390513 - (cons item list) → adds a item to the beginning of list. - The second argument must be a list or NIL (empty list is equivalent to NIL). 2006-08-17 01:43:16.167256 NIL 2006-08-17 02:02:11.398405 - NIL is one of two symbols in Lisp that isn't a keyword but still has itself as its constant value (T is the other symbol that works like this). - The fact that NIL evaluates to itself, combined with () ≡ NIL, means that you can write () rather than (QUOTE ()). 2006-08-17 01:43:16.171654 LIST 2006-08-17 02:02:11.406310 - Constructs a list from its arguments. - (list 1 2 3) → (1 2 3) 2006-08-17 01:43:16.175855 FIRST 2006-08-17 02:02:11.414199 - Returns the first value of a list. - Also known as: CAR 2006-08-17 01:43:16.180061 REST 2006-08-17 02:02:11.422100 - Returns all values of a list except for the first one. - Also known as: CDR 2006-08-17 01:43:16.184277 Binding (let) vs. Assignment (setq) 2006-08-17 02:02:11.430249 - Binding creates a new place to hold a value - Assignment gives an old place a new value (changes the value of an existing binding). 2006-08-17 01:43:16.188478 DEFUN 2006-08-17 02:02:11.438717 - Defines a named function. - Does not evaluate its arguments. - Returns the name of the defined function. Has three arguments: # the name of the function # a list of argument names # the body of the function 2006-08-17 01:43:16.193002 LAMBDA 2006-08-17 02:02:11.446662 - Defines an anonymous (unnamed) function. - Can't be evaluated. - A lambda form must appear only where Lisp expects to find a function -- normally as the first element of a form. Has two arguments: # a list of argument names # the body of the function 2006-08-17 01:43:16.197236 Macros can be considered functions that accept and return abstract syntax trees (Lisp S-expressions). These functions are invoked before the evaluator or compiler to produce the final source code. (defmacro until (test &body body) `(do () (,test) ,@body)) DEFMACRO 2006-08-17 02:02:11.454586 - Defines a named macro. - Has three arguments: a name, a list of argument names, and a body. - Macros return a form, not values. - When Lisp evaluates a call to your macro, it first evaluates the body of your macro definition, then evaluates the result of the first evaluation. 2006-08-17 01:43:16.201682 How does a backquote (`) change the evaluation of a form? 2006-08-17 02:02:11.462614 - Backquotes behave like quotes -- suppressing evaluation of all the enclosed forms -- except where a comma appears within the backquoted form. - A symbol following the comma is evaluated. 2006-08-17 01:43:16.206570 MACROEXPAND 2006-08-17 02:02:11.470579 - A function that shows how a macro body appears before evaluation. - Since MACROEXPAND is a function, it evaluates its arguments. This is why you have to quote the form you want expanded. 2006-08-17 01:43:16.210856 MULTIPLE-VALUE-BIND 2006-08-17 02:02:11.478522 - Binds each value to a separate symbol. - e.g. (multiple-value-bind (a b c) (values 2 3 5) (+ a b c)) - Excess values are ignored. - Excess symbols are bound to NIL. 2006-08-17 01:43:16.215095 PROGN 2006-08-17 02:02:11.486842 (PROGN form1 form2 ... formN) evaluates form1 through formN in order, and returns the value of formN. 2006-08-17 01:43:16.219331 READ, READ-CHAR 2006-08-17 02:02:11.495276 - READ reads the input until enter is pressed. - READ accepts Lisp data. - READ takes an input stream as an optional argument. - READ-CHAR reads one character. 2006-08-17 01:43:16.223685 WRITE, WRITE-CHAR 2006-08-17 02:02:11.503286 - WRITE prints the value so that it could be presented to READ to create the same value. - WRITE-CHAR prints just the readable character, without the extra Lisp syntax (the #\) that would identify it to READ as a character. 2006-08-17 01:43:16.228159 MAKE-ARRAY 2006-08-17 02:02:11.511283 - Takes a list of dimensions and returns an array. - By default, an array can contain any kind of data; optional arguments let you restrict the element data types for the sake of efficiency. - An array's rank is the same as its number of dimensions. 2006-08-17 01:43:16.232415 AREF 2006-08-17 02:02:11.519274 - Retrieves an element of an array. - AREF's first argument is the array. - The remaining arguments specify the index along each dimension. 2006-08-17 01:43:00 (setf (first mylist) 'n) SETF 2006-08-17 03:05:31.001187 - SETF is similar to SETQ, except where SETQ assigns a value to a symbol, SETF assigns a value to a place. - You can give any (even) number of arguments to setf. 2006-08-17 01:43:16.241265 To set an element of an array ... 2006-08-17 02:02:11.535308 ... use AREF inside a SETF form. 2006-08-17 01:43:16.245540 Vectors 2006-08-17 02:02:11.543335 - Vectors are one-dimensional arrays. - You can create a vector using MAKE-ARRAY, and access its elements using AREF. - - e.g. (make-array 3). - You can create a vector from a list of values, using the VECTOR form. 2006-08-17 01:43:16.249794 ELT 2006-08-17 02:02:11.551443 - (elt sequence index) - Accesses the element of sequence specified by index. 2006-08-17 01:43:16.254048 STRING 2006-08-17 02:02:11.559472 Changes characters or symbols to strings. 2006-08-17 01:43:16.258301 LENGTH 2006-08-17 02:02:11.567499 Returns the length of a sequence. 2006-08-17 01:43:16.262813 MAKE-STRING 2006-08-17 02:02:11.575559 - make-string size {&key initial-element element-type} => string - make-string returns a simple string of length size whose elements have been initialized to initial-element. 2006-08-17 01:43:16.267056 Properties are less often used in modern Lisp programs. Hash tables (see below), structures (described in the next section), and CLOS objects (see Chapter 7 and Chapter 14) provide all of the capabilities of property lists in ways that are easier to use and more efficient. A symbol's property list ... 2006-08-17 02:02:11.583614 - ... is like a miniature database which associates a number of key/value pairs with the symbol. - e.g. (setf (get 'object-1 'color) 'red) - (get 'object-1 'color) → red 2006-08-17 01:43:16.271567 TYPE-OF 2006-08-17 02:02:11.591678 TYPE-OF returns a symbol or a list indicating the type of its argument. 2006-08-17 01:43:16.275835 What is a structure? 2006-08-17 02:02:11.599741 A Lisp structure gives you a way to create an object which stores related data in named slots. 2006-08-17 01:43:16.280103 DEFSTRUCT 2006-08-17 02:02:11.607826 - e.g. (defstruct struct-1 color size shape position weight) - Defines a structured type, named struct-1, with named slots as specified by the slot-options (color, size, ...). - Lisp generates the make-_structname_ and _structname-slotname_ functions when you define a structure using DEFSTRUCT. 2006-08-17 01:43:16.284386 MAKE-_STRUCTNAME_ 2006-08-17 02:02:11.615919 Creates a new structure of type STRUCTNAME (which was defined before). 2006-08-17 01:43:16.288666 _STRUCTNAME-SLOTNAME_ 2006-08-17 02:02:11.623984 - (_STRUCTNAME-SLOTNAME_ object1) - Function that accesses slots of a struct instance assigned to the variable object1. 2006-08-17 01:43:16.292935 A hash table ... 2006-08-17 02:02:11.632072 - ... associates a value with a unique key. - Unlike a property list, a hash table is well suited to a large number of key/value pairs, but suffers from excessive overhead for smaller sets of associations. 2006-08-17 01:43:16.297209 MAKE-HASH-TABLE 2006-08-17 02:02:11.640383 Creates and returns a new hash table. 2006-08-17 01:43:16.301471 - If you want to use numbers for keys, you must create a hash table using the form: (make-hash-table :test #'eql) - If you want to use lists for keys, create your hash table with: (make-hash-table :test #'equal) GETHASH 2006-08-17 02:02:11.648543 - (gethash key hash-table) - Accesses values of a hash table. - Returns two values: The first is the value associated with the key. The second is T if the key was found, and NIL otherwise. 2006-08-17 01:43:16.305976 REMHASH 2006-08-17 02:02:11.656764 - (REMHASH key hash-table) - Removes a key from a hash table. 2006-08-17 01:43:16.310526 (setf (gethash 'baz ht1) 'baz-value) If you want to change the value for a hash table key ... 2006-08-17 02:02:11.664885 ... use GETHASH with SETF, just as if you were adding a new key/value pair. 2006-08-17 01:43:16.314812 DEFPACKAGE 2006-08-17 02:02:11.673027 - The DEFPACKAGE macro provides most package operations. - e.g. (defpackage util1 (:export init func1 func2) (:use common-lisp)) - The :USE option specifies that names from another package may be used without qualification - The :IMPORT-FROM options bring in specific names. - The :EXPORT option specifies the names that are exposed to clients of the package. 2006-08-17 01:43:16.319105 IN-PACKAGE 2006-08-17 02:02:11.681185 The IN-PACKAGE macro sets the current package. 2006-08-17 01:43:16.323361 USE-PACKAGE 2006-08-17 02:02:11.689347 The USE-PACKAGE form causes the current (or a given) package to inherit all the external symbols of the named packages. 2006-08-17 01:43:16.327712 - PRIN1 behaves as PRINT, but does not surround its output with whitespace. - PRINC behaves as PRIN1, but generates output intended for display, rather than READ; for example, PRINC omits the quotes around a string, and does not print escape characters. PRINT 2006-08-17 02:02:11.697526 - The PRINT function changes a Lisp object into the sequence of characters that READ would need to reconstruct it. - Takes an output stream as an optional argument. 2006-08-17 01:43:16.332204 OPEN 2006-08-17 02:02:11.705798 - Attaches a stream to a file. - e.g. (setq out-stream (open "my-temp-file" :direction :output)) - e.g. (setq in-stream (open "my-temp-file" :direction :input)) - To finish operations on the stream and close the associated file, use the CLOSE function. 2006-08-17 01:43:16.336694 6 Characters Which characters are reserved for the programmer? 2006-08-17 02:02:11.714138 [ ] { } ! ? 2006-08-17 01:43:16.340973 READ-DELIMITED-LIST 2006-08-17 02:02:11.722373 - Expects one argument: The terminating character. - The other two arguments are optional -- the input stream and a flag which is normally set to T when used in reader macro functions. - Reads objects from the input stream until it encounters the terminating character, then returns all of the objects in a list. 2006-08-17 01:43:16.345548 What does `',form do? 2006-08-17 02:02:11.730597 Evaluates form and returns the result, quoted. 2006-08-17 01:10:00 SET-MACRO-CHARACTER 2006-08-17 02:02:11.738816 - (set-macro-character char new-function) - causes char to be a macro character associated with the reader macro function new-function. 2006-08-17 01:11:00 GET-MACRO-CHARACTER 2006-08-17 02:02:11.747048 - (get-macro-character char) - returns as its primary value, function, the reader macro function associated with char. 2006-08-17 01:43:16.358427 - (defun open-bracket-macro-character (stream char) `',(read-delimited-list #\] stream t)) - (set-macro-character #\[ #'open-bracket-macro-character) - (set-macro-character #\] (get-macro-character #\))) Reader macro function 2006-08-17 02:02:11.755293 - You can use reader macros to alter the behavior of the Lisp reader. - Every reader macro function gets called with two arguments: the input stream and the character that caused the macro to be invoked. 2006-08-17 01:56:28.639815 LISTP 2006-08-17 02:02:11.763520 A function that returns true if its argument is a list. 2006-08-17 02:00:35.640696 NULL / NOT 2006-08-17 02:02:11.771748 Returns true of the empty list / if the argument is false (NIL). 2006-08-17 02:04:40.323243 AND 2006-08-17 02:04:40.323243 If all arguments are true (that is, not nil), then AND returns the value of the last one. 2006-08-17 02:05:40.619214 OR 2006-08-17 02:05:40.619214 Returns the first argument that is not NIL. 2006-08-17 02:26:00 (format t "~A plus ~A equals ~A.~%" 2 3 (+ 2 3)) FORMAT 2006-08-17 02:27:15.942398 - The most general output function. - The first argument indicates where the output is to be printed, - the second is a string template, - the remaining arguments are usually objects whose printed representations are to be inserted into the template. 2006-08-17 02:56:00 DEFPARAMETER 2006-08-17 02:57:07.671183 - Creates a global variable. - It's conventional to give global variables names that begin and end with asterisks. 2006-08-17 02:57:58.646366 DEFCONSTANT 2006-08-17 02:57:58.646366 - Creates a global constant. - Raises an error if the name given already exists. 2006-08-17 02:58:54.192341 BOUNDP 2006-08-17 02:58:54.192341 Returns true if a symbol is the name of a global variable or constant. 2006-08-17 03:07:26.795386 (remove 'a lst) REMOVE 2006-08-17 03:07:26.795386 Returns a new list that doesn't contain the value given as an argument to REMOVE. 2006-08-17 13:53:00 DO 2006-08-17 13:54:33.826183 - The do macro is the fundamental iteration operator in Common Lisp. - The first argument is a list of variable specifications, each of the form (variable initial update), e.g. (i 0 (+ i 1)). - The second argument to do should be a list containing one or more expressions. The first expression is used to test whether iteration should stop. The remaining expressions in this list will be evaluated in order when iteration stops, and the value of the last will be returned as the value of the do. - The remaining arguments to do comprise the body of the loop. They will be evaluated, in order, on each iteration. 2006-08-17 13:58:01.962034 DOLIST 2006-08-17 13:58:01.962034 - DOLIST takes an argument of the form (obj lst), followed by a body of expressions. - The body will be evaluated with variable bound to successive elements of the list returned by expression. 2006-08-17 14:00:00 FUNCTION 2006-08-17 14:03:14.702236 - If we give the name of a function to _function_, it will return the associated object (a function). - Like quote, function is a special operator, so we don't have to quote the argument. - #' is an abbreviation for FUNCTION. 2006-08-17 14:04:48.693920 APPLY 2006-08-17 14:04:48.693920 - takes a function and a list of arguments for it, - returns the result of applying the function to the arguments. 2006-08-17 14:06:00 FUNCALL 2006-08-17 14:06:44.341117 - takes a function as its first argument, - calls the function with the remaining arguments. 2006-08-17 14:14:17.041778 TYPEP 2006-08-17 14:14:17.041778 - The function typep takes an object and a type specifier, and returns true if the object is of that type. - e.g. (typep 27 'integer)