Copyright (c) 1980 The Regents of the University of California.
All rights reserved.
%sccs.include.redist.roff%
@(#)chb.n 6.2 (Berkeley) 04/17/91
." $Header: /na/franz/doc/RCS/chb.n,v 1.1 83/01/31 07:11:40 jkf Exp $ .Ap 2 Special Symbols .pp The values of these symbols have a predefined meaning. Some values are counters while others are simply flags whose value the user can change to affect the operation of lisp system. In all cases, only the value cell of the symbol is important, the function cell is not. The value of some of the symbols (like ER%misc) are functions - what this means is that the value cell of those symbols either contains a lambda expression, a binary object, or symbol with a function binding. .pp The values of the special symbols are: \\$1 - \\ .. .Sa $gccount$ The number of garbage collections which have occurred. .Sa $gcprint If bound to a non nil value, then after each garbage collection and subsequent storage allocation a summary of storage allocation will be printed. .Sa $ldprint If bound to a non nil value, then during each .i fasl or .i cfasl a diagnostic message will be printed. .Sa ER%all The function which is the error handler for all errors (see \(sc10) .Sa ER%brk The function which is the handler for the error signal generated by the evaluation of the .i break function (see \(sc10). .Sa ER%err The function which is the handler for the error signal generated by the evaluation of the .i err function (see \(sc10). .Sa ER%misc The function which is the handler of the error signal generated by one of the unclassified errors (see \(sc10). Most errors are unclassified at this point. .Sa ER%tpl The function which is the handler to be called when an error has occurred which has not been handled (see \(sc10). .Sa ER%undef The function which is the handler for the error signal generated when a call to an undefined function is made. .Sa ^w When bound to a non nil value this will prevent output to the standard output port (poport) from reaching the standard output (usually a terminal). Note that ^w is a two character symbol and should not be confused with ^W which is how we would denote control-w. The value of ^w is checked when the standard output buffer is flushed which occurs after a .i terpr , .i drain or when the buffer overflows. This is most useful in conjunction with ptport described below. System error handlers rebind ^w to nil when they are invoked to assure that error messages are not lost. (This was introduced for Maclisp compatibility). .Sa defmacro-for-compiling The has an effect during compilation. If non-nil it causes macros defined by defmacro to be compiled and included in the object file. .Sa environment The UNIX environment in assoc list form. .Sa errlist When a .i reset is done, the value of errlist is saved away and control is thrown to the top level. Eval is then mapped over the saved away value of this list. .Sa errport This port is initially bound to the standard error file. .Sa evalhook The value of this symbol, if bound, is the name of a function to handle evalhook traps (see \(sc14.4) .Sa float-format The value of this symbol is a string which is the format to be used by print to print flonums. See the documentation on the UNIX function printf for a list of allowable formats. .Sa funcallhook The value of this symbol, if bound, is the name of a function to handle funcallhook traps (see \(sc14.4). .Sa gcdisable If non nil, then garbage collections will not be done automatically when a collectable data type runs out. .Sa ibase This is the input radix used by the lisp reader. It may be either eight or ten. Numbers followed by a decimal point are assumed to be decimal regardless of what ibase is. .Sa linel The line length used by the pretty printer, pp. This should be used by .i print but it is not at this time. .Sa nil This symbol represents the null list and thus can be written (). Its value is always nil. Any attempt to change the value will result in an error. .Sa piport Initially bound to the standard input (usually the keyboard). A read with no arguments reads from piport. .Sa poport Initially bound to the standard output (usually the terminal console). A print with no second argument writes to poport. See also: ^w and ptport. .Sa prinlength If this is a positive fixnum, then the print function will print no more than prinlength elements of a list or hunk and further elements abbreviated as `...'. The initial value of prinlength is nil. .Sa prinlevel If this is a positive fixnum, then the print function will print only prinlevel levels of nested lists or hunks. Lists below this level will be abbreviated by `&' and hunks below this level will be abbreviated by a `%'. The initial value of prinlevel is nil. .Sa ptport Initially bound to nil. If bound to a port, then all output sent to the standard output will also be sent to this port as long as this port is not also the standard output (as this would cause a loop). Note that ptport will not get a copy of whatever is sent to poport if poport is not bound to the standard output. .Sa readtable The value of this is the current readtable. It is an array but you should NOT try to change the value of the elements of the array using the array functions. This is because the readtable is an array of bytes and the smallest unit the array functions work with is a full word (4 bytes). You can use .i setsyntax to change the values and .i "(status syntax ...)" to read the values. .Sa t This symbol always has the value t. It is possible to change the value of this symbol for short periods of time but you are strongly advised against it. .Sa top-level In a lisp system without /usr/lib/lisp/toplevel.l loaded, after a .i reset is done, the lisp system will .i funcall the value of top-level if it is non nil. This provides a way for the user to introduce his own top level interpreter. When /usr/lib/lisp/toplevel.l is loaded, it sets top-level to franz-top-level and changes the .i reset function so that once franz-top-level starts, it cannot be replaced by changing top-level. Franz-top-level does provide a way of changing the top level however, and that is through user-top-level. .Sa user-top-level If this is bound then after a .i reset , the top level function will .i funcall the value of this symbol rather than go through a read eval print loop.
All rights reserved.
%sccs.include.redist.roff%
@(#)chb.n 6.2 (Berkeley) 04/17/91
." $Header: /na/franz/doc/RCS/chb.n,v 1.1 83/01/31 07:11:40 jkf Exp $ .Ap 2 Special Symbols .pp The values of these symbols have a predefined meaning. Some values are counters while others are simply flags whose value the user can change to affect the operation of lisp system. In all cases, only the value cell of the symbol is important, the function cell is not. The value of some of the symbols (like ER%misc) are functions - what this means is that the value cell of those symbols either contains a lambda expression, a binary object, or symbol with a function binding. .pp The values of the special symbols are: \\$1 - \\ .. .Sa $gccount$ The number of garbage collections which have occurred. .Sa $gcprint If bound to a non nil value, then after each garbage collection and subsequent storage allocation a summary of storage allocation will be printed. .Sa $ldprint If bound to a non nil value, then during each .i fasl or .i cfasl a diagnostic message will be printed. .Sa ER%all The function which is the error handler for all errors (see \(sc10) .Sa ER%brk The function which is the handler for the error signal generated by the evaluation of the .i break function (see \(sc10). .Sa ER%err The function which is the handler for the error signal generated by the evaluation of the .i err function (see \(sc10). .Sa ER%misc The function which is the handler of the error signal generated by one of the unclassified errors (see \(sc10). Most errors are unclassified at this point. .Sa ER%tpl The function which is the handler to be called when an error has occurred which has not been handled (see \(sc10). .Sa ER%undef The function which is the handler for the error signal generated when a call to an undefined function is made. .Sa ^w When bound to a non nil value this will prevent output to the standard output port (poport) from reaching the standard output (usually a terminal). Note that ^w is a two character symbol and should not be confused with ^W which is how we would denote control-w. The value of ^w is checked when the standard output buffer is flushed which occurs after a .i terpr , .i drain or when the buffer overflows. This is most useful in conjunction with ptport described below. System error handlers rebind ^w to nil when they are invoked to assure that error messages are not lost. (This was introduced for Maclisp compatibility). .Sa defmacro-for-compiling The has an effect during compilation. If non-nil it causes macros defined by defmacro to be compiled and included in the object file. .Sa environment The UNIX environment in assoc list form. .Sa errlist When a .i reset is done, the value of errlist is saved away and control is thrown to the top level. Eval is then mapped over the saved away value of this list. .Sa errport This port is initially bound to the standard error file. .Sa evalhook The value of this symbol, if bound, is the name of a function to handle evalhook traps (see \(sc14.4) .Sa float-format The value of this symbol is a string which is the format to be used by print to print flonums. See the documentation on the UNIX function printf for a list of allowable formats. .Sa funcallhook The value of this symbol, if bound, is the name of a function to handle funcallhook traps (see \(sc14.4). .Sa gcdisable If non nil, then garbage collections will not be done automatically when a collectable data type runs out. .Sa ibase This is the input radix used by the lisp reader. It may be either eight or ten. Numbers followed by a decimal point are assumed to be decimal regardless of what ibase is. .Sa linel The line length used by the pretty printer, pp. This should be used by .i print but it is not at this time. .Sa nil This symbol represents the null list and thus can be written (). Its value is always nil. Any attempt to change the value will result in an error. .Sa piport Initially bound to the standard input (usually the keyboard). A read with no arguments reads from piport. .Sa poport Initially bound to the standard output (usually the terminal console). A print with no second argument writes to poport. See also: ^w and ptport. .Sa prinlength If this is a positive fixnum, then the print function will print no more than prinlength elements of a list or hunk and further elements abbreviated as `...'. The initial value of prinlength is nil. .Sa prinlevel If this is a positive fixnum, then the print function will print only prinlevel levels of nested lists or hunks. Lists below this level will be abbreviated by `&' and hunks below this level will be abbreviated by a `%'. The initial value of prinlevel is nil. .Sa ptport Initially bound to nil. If bound to a port, then all output sent to the standard output will also be sent to this port as long as this port is not also the standard output (as this would cause a loop). Note that ptport will not get a copy of whatever is sent to poport if poport is not bound to the standard output. .Sa readtable The value of this is the current readtable. It is an array but you should NOT try to change the value of the elements of the array using the array functions. This is because the readtable is an array of bytes and the smallest unit the array functions work with is a full word (4 bytes). You can use .i setsyntax to change the values and .i "(status syntax ...)" to read the values. .Sa t This symbol always has the value t. It is possible to change the value of this symbol for short periods of time but you are strongly advised against it. .Sa top-level In a lisp system without /usr/lib/lisp/toplevel.l loaded, after a .i reset is done, the lisp system will .i funcall the value of top-level if it is non nil. This provides a way for the user to introduce his own top level interpreter. When /usr/lib/lisp/toplevel.l is loaded, it sets top-level to franz-top-level and changes the .i reset function so that once franz-top-level starts, it cannot be replaced by changing top-level. Franz-top-level does provide a way of changing the top level however, and that is through user-top-level. .Sa user-top-level If this is bound then after a .i reset , the top level function will .i funcall the value of this symbol rather than go through a read eval print loop.