4.1cBSD/usr/src/ucb/lisp/lisplib/manual/ch1.r
CHAPTER 1
FRANZ LISP
1.1. FRANZ LISP[] was created as a tool to further research
in symbolic and algebraic manipulation, artificial intelli-
gence, and programming languages at the University of Cali-
fornia at Berkeley. Its roots are in the PDP-11 Lisp system
which originally came from Harvard. As it grew it adopted
features of Maclisp and Lisp Machine Lisp which enables our
work to be shared with colleagues at the Laboratory for Com-
puter Science at M.I.T. Substantial compatibility with
other Lisp dialects (Interlisp, UCILisp, CMULisp) is
achieved by means of support packages and compiler switches.
FRANZ LISP is written almost entirely in the programming
language C. A small part is written in the assembler
language for the current host machine, a VAX 11/780, and
part is written in Lisp. Because FRANZ LISP is written in
C, it is relatively portable and easy to comprehend.
FRANZ LISP is capable of running large lisp programs in
a timesharing environment, has facilities for arrays and
user defined structures, has a user controlled reader with
character and word macro capabilities, and can interact
directly with compiled Lisp, C, Fortran, and Pascal code.
This document is a reference manual for the FRANZ LISP
system. It is not a Lisp primer or introduction to the
language. Some parts will be of interest only to those
maintaining FRANZ LISP at their computer site. This docu-
ment is divided into four Movements. In the first one we
will attempt to describe the language of FRANZ LISP pre-
cisely and completely as it now stands (Opus 38, April
1982). In the second Movement we will look at the reader,
function types, arrays and exception handling. In the third
Movement we will look at several large support packages
written to help the FRANZ LISP user, namely the trace pack-
age, compiler, fixit and stepping package. Finally the
fourth movement contains an index into the other movements.
____________________
9 []It is rumored that this name has something to do with
Franz Liszt [F_rants List] (1811-1886) a Hungarian composer
and keyboard virtuoso. These allegations have never been
proven.
9FRANZ LISP 1-1
FRANZ LISP 1-2
In the rest of this chapter we shall examine the data types
of FRANZ LISP. The conventions used in the description of
the FRANZ LISP functions will be given in section 1.4 -- it
is very important that these conventions are understood.
1.2. Data Types FRANZ LISP has eleven data types. In
this section we shall look in detail at each type and if a
type is divisible we shall look inside it. There is a Lisp
function _t_y_p_e which will return the type name of a lisp
object. This is the official FRANZ LISP name for that type
and we will use this name and this name only in the manual
to avoid confusing the reader. The types are listed in
terms of importance rather than alphabetically.
1.2.0. lispval This is the name we use to describe any
lisp object. The function _t_y_p_e will never return `lispval'.
1.2.1. symbol This object corresponds to a variable in
most other programming languages. It may have a value or
may be `unbound'. A symbol may be _l_a_m_b_d_a _b_o_u_n_d meaning that
its current value is stored away somewhere and the symbol
is given a new value for the duration of a certain context.
When the Lisp processor leaves that context, the symbol's
current value is thrown away and its old value is restored.
9A symbol may also have a _f_u_n_c_t_i_o_n _b_i_n_d_i_n_g. This function
binding is static; it cannot be lambda bound. Whenever the
symbol is used in the functional position of a Lisp expres-
sion the function binding of the symbol is examined (see
Chapter 4 for more details on evaluation).
9A symbol may also have a _p_r_o_p_e_r_t_y _l_i_s_t, another static data
structure. The property list consists of a list of an even
number of elements, considered to be grouped as pairs. The
first element of the pair is the _i_n_d_i_c_a_t_o_r the second the
_v_a_l_u_e of that indicator.
9Each symbol has a print name (_p_n_a_m_e) which is how this sym-
bol is accessed from input and referred to on (printed)
output.
9A symbol also has a hashlink used to link symbols together
in the oblist -- this field is inaccessible to the lisp
user.
9Symbols are created by the reader and by the functions
9 Printed: September 21, 1982
FRANZ LISP 1-3
_c_o_n_c_a_t, _m_a_k_n_a_m and their derivatives. Most symbols live on
FRANZ LISP's sole _o_b_l_i_s_t, and therefore two symbols with the
same print name are usually the exact same object (they are
_e_q). Symbols which are not on the oblist are said to be
_u_n_i_n_t_e_r_n_e_d. The function _m_a_k_n_a_m creates uninterned symbols
while _c_o_n_c_a_t creates _i_n_t_e_r_n_e_d ones.
8____________________________________________________________
Subpart name Get value Set value Type
8________________________________________________________________________________________________________________________
value eval set lispval
setq
8____________________________________________________________
property plist setplist list or nil
list get putprop
8____________________________________________________________
function getd putd array, binary, list
binding def or nil
8____________________________________________________________
print name get_pname string
8____________________________________________________________
hash link
8____________________________________________________________
7|7|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|7|
1.2.2. list A list cell has two parts, called the car and
cdr. List cells are created by the function _c_o_n_s.
8 ________________________________________________
Subpart name Get value Set value Type
8 ________________________________________________________________________________________________
car car rplaca lispval
8 ________________________________________________
cdr cdr rplacd lispval
8 ________________________________________________
7 |8|7|7|7|7|
9 |8|7|7|7|7|
9 |8|7|7|7|7|
9 |8|7|7|7|7|
9 |8|7|7|7|7|
9
1.2.3. binary This type acts as a function header for
machine coded functions. It has two parts, a pointer to the
start of the function and a symbol whose print name
describes the argument _d_i_s_c_i_p_l_i_n_e. The discipline (if
_l_a_m_b_d_a, _m_a_c_r_o or _n_l_a_m_b_d_a) determines whether the arguments
to this function will be evaluated by the caller before this
function is called. If the discipline is a string (either
"_s_u_b_r_o_u_t_i_n_e", "_f_u_n_c_t_i_o_n", "_i_n_t_e_g_e_r-_f_u_n_c_t_i_o_n", or "_r_e_a_l-
_f_u_n_c_t_i_o_n") then this function is a foreign subroutine or
function (see 8.4 for more details on this). Although the
type of the _e_n_t_r_y field of a binary type object is either
9 Printed: September 21, 1982
FRANZ LISP 1-4
string or fixnum, the object pointed to is actually a
sequence of machine instructions.
Objects of type binary are created by _m_f_u_n_c_t_i_o_n.
8 _________________________________________________________
Subpart name Get value Set value Type
8 __________________________________________________________________________________________________________________
entry getentry string or fixnum
8 _________________________________________________________
discipline getdisc putdisc symbol or fixnum
8 _________________________________________________________
7|8|7|7|7|7|
9 |8|7|7|7|7|
9 |8|7|7|7|7|
9 |8|7|7|7|7|
9 |8|7|7|7|7|
9
1.2.4. fixnum A fixnum is an integer constant in the
range -2[31] to 2[31]-1. Small fixnums (-1024 to 1023) are
stored in a special table so they needn't be allocated each
time one is needed.
1.2.5. flonum A flonum is a double precision real number
in the range +_2.9x10[-37] to +_1.7x10[38]. There are approx-
imately sixteen decimal digits of precision.
1.2.6. bignum A bignum is an integer of potentially
unbounded size. When integer arithmetic exceeds the limits
mentioned above the calculation is automatically done with
bignums. Should calculation with bignums give a result
which can be represented as a fixnum, then the fixnum
representation will be used[]. This contraction is known as
_i_n_t_e_g_e_r _n_o_r_m_a_l_i_z_a_t_i_o_n. Many Lisp functions assume that
integers are normalized. Bignums are composed of a sequence
of list cells and a cell known as an sdot. The user should
consider a bignum structure indivisible and use functions
such as _h_a_i_p_a_r_t, and _b_i_g_n_u_m-_l_e_f_t_s_h_i_f_t to extract parts of
it.
____________________
9 []The current algorithms for integer arithmetic opera-
tions will return (in certain cases) a result between +_2[30]
and 2[31] as a bignum although this could be represented as
a fixnum.
9 Printed: September 21, 1982
FRANZ LISP 1-5
1.2.7. string A string is a null terminated sequence of
characters. Most functions of symbols which operate on the
symbol's print name will also work on strings. The default
reader syntax is set so that a sequence of characters sur-
rounded by double quotes is a string.
1.2.8. port A port is a structure which the system I/O
routines can reference to transfer data between the Lisp
system and external media. Unlike other Lisp objects there
are a very limited number of ports (20). Ports are allo-
cated by _i_n_f_i_l_e and _o_u_t_f_i_l_e and deallocated by _c_l_o_s_e and
_r_e_s_e_t_i_o. The _p_r_i_n_t function prints a port as a percent sign
followed by the name of the file it is connected to. The
file names $stdin, $stdout and $stderr refer to the standard
input, output and error files.
1.2.9. array Arrays are rather complicated types and are
fully described in Chapter 9. An array consists of a block
of contiguous data, a function to access that data and auxi-
liary fields for use by the accessing function. Since an
array's accessing function is created by the user, an array
can have any form the user chooses (e.g. n-dimensional, tri-
angular, or hash table).
Arrays are created by the function _m_a_r_r_a_y.
8_______________________________________________________________
Subpart name Get value Set value Type
8______________________________________________________________________________________________________________________________
access function getaccess putaccess binary, list
or symbol
8_______________________________________________________________
auxiliary getaux putaux lispval
8_______________________________________________________________
data arrayref replace block of contiguous
set lispval
8_______________________________________________________________
length getlength putlength fixnum
8_______________________________________________________________
delta getdelta putdelta fixnum
8_______________________________________________________________
7|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|
9 Printed: September 21, 1982
FRANZ LISP 1-6
1.2.10. value A value cell contains a pointer to a
lispval. This type is used mainly by arrays of general lisp
objects. Value cells are created with the _p_t_r function. A
value cell containing a pointer to the symbol `foo' is
printed as `(ptr to)foo'
1.2.11. hunk A hunk is a vector of from 1 to 128
lispvals. Once a hunk is created (by _h_u_n_k or _m_a_k_h_u_n_k) it
cannot grow or shrink. The access time for an element of a
hunk is slower than a list cell element but faster than an
array. Hunks are really only allocated in sizes which are
powers of two, but can appear to the user to be any size in
the 1 to 128 range. Users of hunks must realize that
(_n_o_t (_a_t_o_m '_l_i_s_p_v_a_l)) will return true if _l_i_s_p_v_a_l is a hunk.
Most lisp systems do not have a direct test for a list cell
and instead use the above test and assume that a true result
means _l_i_s_p_v_a_l is a list cell. In FRANZ LISP you can use
_d_t_p_r to check for a list cell. Although hunks are not list
cells, you can still access the first two hunk elements with
_c_d_r and _c_a_r and you can access any hunk element with _c_x_r[].
You can set the value of the first two elements of a hunk
with _r_p_l_a_c_d and _r_p_l_a_c_a and you can set the value of any ele-
ment of the hunk with _r_p_l_a_c_x. A hunk is printed by printing
its contents surrounded by { and }. However a hunk cannot
be read in in this way in the standard lisp system. It is
easy to write a reader macro to do this if desired.
1.3. Documentation The conventions used in the following
chapters were designed to give a great deal of information
in a brief space. The first line of a function description
contains the function name in bold face and then lists the
arguments, if any. The arguments all have names which begin
with a letter or letters and an underscore. The letter(s)
gives the allowable type(s) for that argument according to
this table.
____________________
9 []In a hunk, the function _c_d_r references the first ele-
ment and _c_a_r the second.
9 Printed: September 21, 1982
FRANZ LISP 1-7
8 _______________________________________________________
Letter Allowable type(s)
8 ______________________________________________________________________________________________________________
g any type
8 _______________________________________________________
s symbol (although nil may not be allowed)
8 _______________________________________________________
t string
8 _______________________________________________________
l list (although nil may be allowed)
8 _______________________________________________________
n number (fixnum, flonum, bignum)
8 _______________________________________________________
i integer (fixnum, bignum)
8 _______________________________________________________
x fixnum
8 _______________________________________________________
b bignum
8 _______________________________________________________
f flonum
8 _______________________________________________________
u function type (either binary or lambda body)
8 _______________________________________________________
y binary
8 _______________________________________________________
a array
8 _______________________________________________________
v value
8 _______________________________________________________
p port (or nil)
8 _______________________________________________________
h hunk
8 _______________________________________________________
7 |7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|
|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|7|
In the first line of a function description, those arguments
preceded by a quote mark are evaluated (usually before the
function is called). The quoting convention is used so that
we can give a name to the result of evaluating the argument
and we can describe the allowable types. If an argument is
not quoted it does not mean that that argument will not be
evaluated, but rather that if it is evaluated, the time at
which it is evaluated will be specifically mentioned in the
function description. Optional arguments are surrounded by
square brackets. An ellipsis means zero or more occurrences
of an argument of the directly preceding type.
9 Printed: September 21, 1982