C

*Class

A global variable holding the current class. See also OO Concepts, class, extend, dm and var and rel.

: (class +Test)
-> +Test
: *Class
-> +Test

(cache 'var 'sym . prg) -> any

Speeds up some calculations, by holding previously calculated results in an idx tree structure. Such an optimization is sometimes called "memoization". sym must be a transient symbol representing a unique key for the argument(s) to the calculation. See also hash.

: (de fibonacci (N)
   (cache '(NIL) (pack (char (hash N)) N)
      (if (> 2 N)
         1
         (+
            (fibonacci (dec N))
            (fibonacci (- N 2)) ) ) ) )
-> fibonacci
: (fibonacci 22)
-> 28657
: (fibonacci 10000)
-> 5443837311356528133873426099375038013538 ...  # (2090 digits)

(call 'any ..) -> flg

Calls an external system command. The any arguments specify the command and its arguments. Returns T if the command was executed successfully.

: (when (call 'test "-r" "file.l")  # Test if file exists and is readable
   (load "file.l")  # Load it
   (call 'rm "file.l") )  # Remove it

call/1

Pilog predicate that succeeds if the argument term can be proven.

: (be mapcar (@ NIL NIL))
-> mapcar
: (be mapcar (@P (@X . @L) (@Y . @M))
   (call @P @X @Y)                        # Call the given predicate
   (mapcar @P @L @M) )
-> mapcar
:  (? (mapcar change (you are a computer) @Z))
-> NIL
:  (? (mapcar change (you are a computer) @Z) T)
-> NIL
:  (? (mapcar permute ((a b c) (d e f)) @X))
 @X=((a b c) (d e f))
 @X=((a b c) (d f e))
 @X=((a b c) (e d f))
 ...
 @X=((a c b) (d e f))
 @X=((a c b) (d f e))
 @X=((a c b) (e d f))
 ...

(can 'msg) -> lst

Returns a list of all classes that accept the message msg. See also OO Concepts, class, dep, what and who.

: (can 'zap>)
-> ((zap> . +relation) (zap> . +Blob) (zap> . +Entity))
: (more @ pp)
(dm (zap> . +relation) (Obj Val))

(dm (zap> . +Blob) (Obj Val)
   (and
      Val
      (call 'rm "-f" (blob Obj (: var))) ) )

(dm (zap> . +Entity) NIL
   (for X (getl This)
      (let V (or (atom X) (pop 'X))
         (and (meta This X) (zap> @ This V)) ) ) )

-> NIL

(car 'var) -> any

List access: Returns the value of var if it is a symbol, or the first element if it is a list. See also cdr and c..r.

: (car (1 2 3 4 5 6))
-> 1

(c[ad]*ar 'var) -> any

(c[ad]*dr 'lst) -> any

List access shortcuts. Combinations of the car and cdr functions, with up to four letters 'a' and 'd'.

: (cdar '((1 . 2) . 3))
-> 2

(case 'any (any1 . prg1) (any2 . prg2) ..) -> any

Multi-way branch: any is evaluated and compared to the CAR elements anyN of each clause. If one of them is a list, any is in turn compared to all elements of that list. T is a catch-all for any value. If a comparison succeeds, prgN is executed, and the result returned. Otherwise NIL is returned. See also state.

: (case (char 66) ("A" (+ 1 2 3)) (("B" "C") "Bambi") ("D" (* 1 2 3)))
-> "Bambi"

(catch 'any . prg) -> any

Sets up the environment for a non-local jump which may be caused by throw or by a runtime error. If any is an atom, it is used by throw as a jump label (with T being a catch-all for any label), and a throw called during the execution of prg will immediately return the thrown value. Otherwise, any should be a list of strings, to catch any error whose message contains one of these strings, and this will immediately return the matching string. If neither throw nor an error occurs, the result of prg is returned. See also finally, quit and Error Handling.

: (catch 'OK (println 1) (throw 'OK 999) (println 2))
1
-> 999
: (catch '("No such file") (in "doesntExist" (foo)))
-> "No such file"

(cd 'any) -> sym

Changes the current directory to any. The old directory is returned on success, otherwise NIL. See also dir and pwd.

: (when (cd "lib")
   (println (sum lines (dir)))
   (cd @) )
10955

(cdr 'lst) -> any

List access: Returns all but the first element of lst. See also car and c..r.

: (cdr (1 2 3 4 5 6))
-> (2 3 4 5 6)

(center 'cnt|lst 'any ..) -> sym

Returns a transient symbol with all any arguments packed in a centered format. Trailing blanks are omitted. See also align, tab and wrap.

: (center 4 12)
-> " 12"
: (center 4 "a")
-> " a"
: (center 7 "a")
-> "   a"
: (center (3 3 3) "a" "b" "c")
-> " a  b  c"

(chain 'lst ..) -> lst

Concatenates (destructively) one or several new list elements lst to the end of the list in the current make environment. This operation is efficient also for long lists, because a pointer to the last element of the result list is maintained. chain returns the last linked argument. See also link, yoke and made.

: (make (chain (list 1 2 3) NIL (cons 4)) (chain (list 5 6)))
-> (1 2 3 4 5 6)

(char) -> sym

(char 'cnt) -> sym

(char T) -> sym

(char 'sym) -> cnt

When called without arguments, the next character from the current input stream is returned as a single-character transient symbol, or NIL upon end of file. When called with a number cnt, a character with the corresponding unicode value is returned. As a special case, T is accepted to produce a byte value greater than any first byte in a UTF-8 character (used as a top value in comparisons). Otherwise, when called with a symbol sym, the numeric unicode value of the first character of the name of that symbol is returned. See also peek, skip, key, line, till and eof.

: (char)                   # Read character from console
A                          # (typed 'A' and a space/return)
-> "A"
: (char 100)               # Convert unicode to symbol
-> "d"
: (char "d")               # Convert symbol to unicode
-> 100

: (char T)                 # Special case
-> # (not printable)

: (char 0)
-> NIL
: (char NIL)
-> 0

(chdir 'any . prg) -> any

Changes the current directory to any with cd during the execution of prg. Then the previous directory will be restored and the result of prg returned. See also dir and pwd.

: (pwd)
-> "/usr/abu/pico"
: (chdir "src" (pwd))
-> "/usr/abu/pico/src"
: (pwd)
-> "/usr/abu/pico"

(chkTree 'sym ['fun]) -> num

Checks a database tree node (and recursively all sub-nodes) for consistency. Returns the total number of nodes checked. Optionally, fun is called with the key and value of each node, and should return NIL for failure. See also tree and root.

: (show *DB '+Item)
{C} NIL
   sup (7 . {7-3})
   nr (7 . {7-1})    # 7 nodes in the 'nr' tree, base node is {7-1}
   pr (7 . {7-4})
   nm (77 . {7-6})
-> {C}
: (chkTree '{7-1})   # Check that node
-> 7

(chop 'any) -> lst

Returns any as a list of single-character strings. If any is NIL or a symbol with no name, NIL is returned. A list argument is returned unchanged.

: (chop 'car)
-> ("c" "a" "r")
: (chop "Hello")
-> ("H" "e" "l" "l" "o")

(circ 'any ..) -> lst

Produces a circular list of all any arguments by consing them to a list and then connecting the CDR of the last cell to the first cell. See also circ? and list.

: (circ 'a 'b 'c)
-> (a b c .)

(circ? 'any) -> any

Returs the circular (sub)list if any is a circular list, else NIL. See also circ.

: (circ? 'a)
-> NIL
: (circ? (1 2 3))
-> NIL
: (circ? (1 . (2 3 .)))
-> (2 3 .)

(class sym . typ) -> obj

Defines sym as a class with the superclass(es) typ. As a side effect, the global variable *Class is set to obj. See also extend, dm, var, rel, type, isa and object.

: (class +A +B +C +D)
-> +A
: +A
-> (+B +C +D)
: (dm foo> (X) (bar X))
-> foo>
: +A
-> ((foo> (X) (bar X)) +B +C +D)

(clause '(sym . any)) -> sym

Declares a Pilog fact or rule for the sym argument, by concatenating the any argument to the T property of sym. See also be.

: (clause '(likes (John Mary)))
-> likes
: (clause '(likes (John @X) (likes @X wine) (likes @X food)))
-> likes
: (? (likes @X @Y))
 @X=John @Y=Mary
-> NIL

clause/2

Pilog predicate that succeeds if the first argument is a predicate which has the second argument defined as a clause.

: (? (clause append ((NIL @X @X))))
-> T

: (? (clause append @C))
 @C=((NIL @X @X))
 @C=(((@A . @X) @Y (@A . @Z)) (append @X @Y @Z))
-> NIL

(clip 'lst) -> lst

Returns a copy of lst with all whitespace characters or NIL elements removed from both sides. See also trim.

: (clip '(NIL 1 NIL 2 NIL))
-> (1 NIL 2)
: (clip '(" " a " " b " "))
-> (a " " b)

(close 'cnt) -> cnt | NIL

Closes a file descriptor cnt, and returns it when successful. Should not be called inside an out body for that descriptor. See also open, poll, listen and connect.

: (close 2)                            # Close standard error
-> 2

(cmd ['any]) -> sym

When called without an argument, the name of the command that invoked the picolisp interpreter is returned. Otherwise, the command name is set to any. Setting the name may not work on some operating systems. Note that the new name must not be longer than the original one. See also argv, file and Invocation.

$ pil +
: (cmd)
-> "/usr/bin/picolisp"
: (cmd "!/bin/picolust")
-> "!/bin/picolust"
: (cmd)
-> "!/bin/picolust"

(cnt 'fun 'lst ..) -> cnt

Applies fun to each element of lst. When additional lst arguments are given, their elements are also passed to fun. Returns the count of non-NIL values returned from fun.

: (cnt cdr '((1 . T) (2) (3 4) (5)))
-> 2

(collect 'var 'cls ['hook] ['any|beg ['end [var ..]]])

Returns a list of all database objects of class cls, where the values for the var arguments correspond to the any arguments, or where the values for the var arguments are in the range beg .. end. var, cls and hook should specify a tree for cls or one of its superclasses. If additional var arguments are given, the final values for the result list are obtained by applying the get algorithm. See also db, aux, fetch, init and step.

: (collect 'nr '+Item)
-> ({3-1} {3-2} {3-3} {3-4} {3-5} {3-6} {3-8})
: (collect 'nr '+Item 3 6 'nr)
-> (3 4 5 6)
: (collect 'nr '+Item 3 6 'nm)
-> ("Auxiliary Construction" "Enhancement Additive" "Metal Fittings" "Gadget Appliance")
: (collect 'nm '+Item "Main Part")
-> ({3-1})

(commit ['any] [exe1] [exe2]) -> T

Closes a transaction, by writing all new or modified external symbols to, and removing all deleted external symbols from the database. When any is given, it is implicitly sent (with all modified objects) via the tell mechanism to all family members. If exe1 or exe2 are given, they are executed as pre- or post-expressions while the database is locked and protected. See also rollback.

: (pool "db")
-> T
: (put '{1} 'str "Hello")
-> "Hello"
: (commit)
-> T

(con 'lst 'any) -> any

Connects any to the first cell of lst, by (destructively) storing any in the CDR of lst. See also conc.

: (setq C (1 . a))
-> (1 . a)
: (con C '(b c d))
-> (b c d)
: C
-> (1 b c d)

(conc 'lst ..) -> lst

Concatenates all argument lists (destructively). See also append and con.

: (setq  A (1 2 3)  B '(a b c))
-> (a b c)
: (conc A B)                        # Concatenate lists in 'A' and 'B'
-> (1 2 3 a b c)
: A
-> (1 2 3 a b c)                    # Side effect: List in 'A' is modified!

(cond ('any1 . prg1) ('any2 . prg2) ..) -> any

Multi-way conditional: If any of the anyN conditions evaluates to non-NIL, prgN is executed and the result returned. Otherwise (all conditions evaluate to NIL), NIL is returned. See also nond, if, if2 and when.

: (cond
   ((= 3 4) (println 1))
   ((= 3 3) (println 2))
   (T (println 3)) )
2
-> 2

(connect 'any1 'any2) -> cnt | NIL

Tries to establish a TCP/IP connection to a server listening at host any1, port any2. any1 may be either a hostname or a standard internet address in numbers-and-dots/colons notation (IPv4/IPv6). any2 may be either a port number or a service name. Returns a socket descriptor cnt, or NIL if the connection cannot be established. See also listen and udp.

: (connect "localhost" 4444)
-> 3
: (connect "some.host.org" "http")
-> 4

(cons 'any ['any ..]) -> lst

Constructs a new list cell with the first argument in the CAR and the second argument in the CDR. If more than two arguments are given, a corresponding chain of cells is built. (cons 'a 'b 'c 'd) is equivalent to (cons 'a (cons 'b (cons 'c 'd))). See also list.

: (cons 1 2)
-> (1 . 2)
: (cons 'a '(b c d))
-> (a b c d)
: (cons '(a b) '(c d))
-> ((a b) c d)
: (cons 'a 'b 'c 'd)
-> (a b c . d)

(copy 'any) -> any

Copies the argument any. For lists, the top level cells are copied, while atoms are returned unchanged.

: (=T (copy T))               # Atoms are not copied
-> T
: (setq L (1 2 3))
-> (1 2 3)
: (== L L)
-> T
: (== L (copy L))             # The copy is not identical to the original
-> NIL
: (= L (copy L))              # But the copy is equal to the original
-> T

(co 'sym [. prg]) -> any

(64-bit version only) Starts, resumes or stops a coroutine with the tag given by sym. If prg is not given, a coroutine with that tag will be stopped. Otherwise, if a coroutine running with that tag is found (pointer equality is used for comparison), its execution is resumed. Else a new coroutine with that tag is initialized and started. prg will be executed until it either terminates normally, or until yield is called. In the latter case co returns, or transfers control to some other, already running, coroutine. Trying to start more than 64 coroutines will result in a stack overflow error. Also, a coroutine cannot resume itself directly or indirectly. See also stack, catch and throw.

: (de pythag (N)   # A generator function
   (if (=T N)
      (co 'rt)  # Stop
      (co 'rt
         (for X N
            (for Y (range X N)
               (for Z (range Y N)
                  (when (= (+ (* X X) (* Y Y)) (* Z Z))
                     (yield (list X Y Z)) ) ) ) ) ) ) )

: (pythag 20)
-> (3 4 5)
: (pythag 20)
-> (5 12 13)
: (pythag 20)
-> (6 8 10)

(count 'tree) -> num

Returns the number of nodes in a database tree. See also tree and root.

: (count (tree 'nr '+Item))
-> 7

(ctl 'sym . prg) -> any

Waits until a write (exclusive) lock (or a read (shared) lock if the first character of sym is "+") can be set on the file sym, then executes prg and releases the lock. If the files does not exist, it will be created. When sym is NIL, a shared lock is tried on the current innermost I/O channel, and when it is T, an exclusive lock is tried instead. See also in, out, err and pipe.

$ echo 9 >count                           # Write '9' to file "count"
$ pil +
: (ctl ".ctl"                             # Exclusive control, using ".ctl"
   (in "count"
      (let Cnt (read)                     # Read '9'
         (out "count"
            (println (dec Cnt)) ) ) ) )   # Write '8'
-> 8
:
$ cat count                               # Check "count"
8

(ctty 'sym|pid) -> flg

When called with a symbolic argument, ctty changes the current TTY device to sym. Otherwise, the local console is prepared for serving the PicoLisp process with the process ID pid. See also raw.

: (ctty "/dev/tty")
-> T

(curry lst . fun) -> fun

Builds a new function from the list of symbols or symbol-value pairs lst and the functional expression fun. Each member in lst that is a pat? symbol is substituted inside fun by its value. All other symbols in lst are collected into a job environment.

: (de multiplier (@X)
   (curry (@X) (N) (* @X N)) )
-> multiplier
: (multiplier 7)
-> ((N) (* 7 N))
: ((multiplier 7) 3))
-> 21

: (def 'fiboCounter
   (curry ((N1 . 0) (N2 . 1)) (Cnt)
      (do Cnt
         (println
            (prog1
               (+ N1 N2)
               (setq N1 N2  N2 @) ) ) ) ) )
-> fiboCounter
: (pp 'fiboCounter)
(de fiboCounter (Cnt)
   (job '((N2 . 1) (N1 . 0))
      (do Cnt
         (println
            (prog1 (+ N1 N2) (setq N1 N2 N2 @)) ) ) ) )
-> fiboCounter
: (fiboCounter 5)
1
2
3
5
8
-> 8
: (fiboCounter 5)
13
21
34
55
89
-> 89

(cut 'cnt 'var) -> lst

Pops the first cnt elements (CAR) from the stack in var. See also pop and del.

: (setq S '(1 2 3 4 5 6 7 8))
-> (1 2 3 4 5 6 7 8)
: (cut 3 'S)
-> (1 2 3)
: S
-> (4 5 6 7 8)