Command sequence

    This is a sequence of any the following command formats, where
    each command is terminated by a semicolon or newline.  Long command
    lines can be extended by using a back-slash followed by a newline
    character.	When this is done, the prompt shows a double angle
    bracket to indicate that the line is still in progress.  Certain
    cases will automatically prompt for more input in a similar manner,
    even without the back-slash.  The most common case for this is when
    a function is being defined, but is not yet completed.

    Each command sequence terminates only on an end of file.  In
    addition, commands can consist of expression sequences, which are
    described in the next section.


    define a function
    -----------------
    define function(params) { body }
    define function(params) = expression

	This first form defines a full function which can consist
	of declarations followed by many statements which implement
	the function.

	The second form defines a simple function which calculates
	the specified expression value from the specified parameters.
	The expression cannot be a statement.  However, the comma
	and question mark operators can be useful.	Examples of
	simple functions are:

		define sumcubes(a, b) = a^3 + b^3
		define pimod(a) = a % pi()
		define printnum(a, n, p)
		{
		    if (p == 0) {
			print a: "^": n, "=", a^n;
		    } else {
			print a: "^": n, "mod", p, "=", pmod(a,n,p);
		    }
		}


    read calc commands
    ------------------
    read $var
    read -once $var
    read filename
    read -once filename

	This reads definitions from the specified calc resource filename.

	In the 1st and 2nd forms, if var is a global variable string
	value, then the value of that variable is used as a filename.

	The following is equivalent to read lucas.cal or read "lucas.cal":

	    global var = "lucas.cal";
	    read $var;

	In the 3rd or 4th forms, the filename argument is treated
	as a literal string, not a variable.  In these forms, the
	name can be quoted if desired.

	The calculator uses the CALCPATH environment variable to
	search through the specified directories for the filename,
	similarly to the use of the PATH environment variable.
	If CALCPATH is not defined, then a default path which is
	usually ":/usr/local/lib/calc" is used.

	The ".cal" extension is defaulted for input files, so that
	if "filename" is not found, then "filename.cal" is then
	searched for.  The contents of the filename are command
	sequences which can consist of expressions to evaluate or
	functions to define, just like at the top level command level.

	When -once is given, the read command acts like the regular
	read expect that it will ignore filename if is has been
	previously read.

	The read -once form is particularly useful in a resource
	file that needs to read a 2nd resource file.  By using the
	READ -once command, one will not reread that 2nd resource
	file, nor will once risk entering into a infinite READ loop
	(where that 2nd resource file directly or indirectly does
	a READ of the first resource file).

	If the -m mode disallows opening of files for reading,
	this command will be disabled.

	To read a calc resource file without printing various
	messages about defined functions, the "resource_debug"
	config should be set to zero.  For example:

	    read lucas;

	will, by default, print messages such as:

	    lucas(h,n) defined
	    gen_u2(h,n,v1) defined
	    gen_u0(h,n,v1) defined
	    rodseth_xhn(x,h,n) defined
	    gen_v1(h,n) defined
	    ldebug(funct,str) defined
	    legacy_gen_v1(h,n) defined

        When "resource_debug" is zero, such messages are silenced.

	    config("resource_debug", 0),;
	    read lucas;

	To silence such messages on the calc command line, try:

	    calc -p -D :0 'read -once lucas; lucas(1, 23209);'


    write calc commands
    -------------------
    write $var
    write filename

	This writes the values of all global variables to the
	specified filename, in such a way that the file can be
	later read in order to recreate the variable values.
	For speed reasons, values are written as hex fractions.
	This command currently only saves simple types, so that
	matrices, lists, and objects are not saved.	 Function
	definitions are also not saved.

	In the 1st form, if var is a global variable string
	value, then the value of that variable is used as a filename.

	The following is equivalent to write dump.out or
	write "dump.out":

	    global var = "dump.out";
	    write $var;

	In the 2nd form, the filename argument is treated as a literal
	string, not a variable.  In this form, the name can be quoted
	if desired.

	If the -m mode disallows opening of files for writing,
	this command will be disabled.


    quit or exit
    ------------
    quit
    quit string
    exit
    exit string

	The action of these commands depends on where they are used.
	At the interactive level, they will cause calc to exit.
	This is the normal way to leave the calculator.  In any
	other use, they will stop the current calculation as if
	an error had occurred.

	If a string is given, then the string is printed as the reason
	for quitting, otherwise a general quit message is printed.
	The routine name and line number which executed the quit is
	also printed in either case.

	Exit is an alias for quit.

	Quit is useful when a routine detects invalid arguments,
	in order to stop a calculation cleanly.  For example,
	for a square root routine, an error can be given if the
	supplied parameter was a negative number, as in:

		define mysqrt(n)
		{
		    if (! isnum(n))
			quit "non-numeric argument";
		    if (n < 0)
			quit "Negative argument";
		    return sqrt(n);
		}

	See 'more information about abort and quit' below for
	more information.


    abort
    -----
    abort
    abort string

	This command behaves like QUIT except that it will attempt
	to return to the interactive level if permitted, otherwise
	calc exit.

	See 'more information about abort and quit' below for
	more information.


    change current directory
    ------------------------
    cd
    cd dir

	Change the current directory to 'dir'.  If 'dir' is omitted,
	change the current directory to the home directory, if $HOME
	is set in the environment.


    show information
    ----------------
    show item

	This command displays some information where 'item' is
	one of the following:

		blocks		unfreed named blocks
		builtin		built in functions
		config		config parameters and values
		constants	cache of numeric constants
		custom		custom functions if calc -C was used
		errors		new error-values created
		files		open files, file position and sizes
		function	user-defined functions
		globaltypes	global variables
		objfunctions	possible object functions
		objtypes	defined objects
		opcodes 	internal opcodes for function `func'
		sizes		size in octets of calc value types
		realglobals	numeric global variables
		statics		un-scoped static variables
		numbers		calc number cache
		redcdata	REDC data defined
		strings		calc string cache
		literals	calc literal cache

	Only the first 4 characters of item are examined, so:

		show globals
		show global
		show glob

	do the same thing.


    calc help
    ---------
    help $var
    help name

	This displays a help related to 'name' or general
	help of none is given.

	In the 1st form, if var is a global variable string
	value, then the value of that variable is used as a name.

	The following is equivalent to help command or help "command":

	    global var = "command";
	    help $var;

	In the 2nd form, the filename argument is treated as a literal
	string, not a variable.  In this form, the name can be quoted
	if desired.


    =-=

    more information about abort and quit
    =====================================

    Consider the following calc file called myfile.cal:

	print "start of myfile.cal";
	define q() {quit "quit from q()"; print "end of q()"}
	define a() {abort "abort from a()"}
	x = 3;
	{print "start #1"; if (x > 1) q()} print "after #1";
	{print "start #2"; if (x > 1) a()} print "after #2";
	{print "start #3"; if (x > 1) quit "quit from 3rd statement"}
	print "end of myfile.cal";

    The command:

	calc read myfile

    will produce:

	q() defined
	a() defined
	start statement #1
	quit from q()
	after statement #1
	start statement #2
	abort from a()

    The QUIT within the q() function prevented the ``end of q()''
    statement from being evaluated.  This QUIT command caused
    control to be returned to just after the place where q()
    was called.

    Notice that unlike QUIT, the ABORT inside function a() halts
    the processing of statements from the input source (myfile.cal).
    Because calc was not interactive, ABORT causes calc to exit.

    The command:

	calc -i read myfile

    will produce:

	q() defined
	a() defined
	start statement #1
	quit from q()
	after statement #1
	start statement #2
	abort from a()
	;		<==== calc interactive prompt

    because the '-i' calc causes ABORT to drop into an
    interactive prompt.	 However typing a QUIT or ABORT
    at the interactive prompt level will always calc to exit,
    even when calc is invoked with '-i'.

    Also observe that both of these commands:

	cat myfile.cal | calc
	cat myfile.cal | calc -i

    will produce:

	q() defined
	a() defined
	start statement #1
	quit from q()
	after statement #1
	start statement #2
	abort from a()

    The ABORT inside function a() halts the processing of statements
    from the input source (standard input).  Because standard input
    is not a terminal, using '-i' does not force it to drop into
    an interactive prompt.

    If one were to type in the contents of myfile.cal interactively,
    calc will produce:

	; print "start of myfile.cal";
	start of myfile.cal
	; define q() {quit "quit from q()"; print "end of q()"}
	q() defined
	; define a() {abort "abort from a()"}
	a() defined
	; x = 3;
	; {print "start #1"; if (x > 1) q()} print "after #1";
	start statement #1
	quit from q()
	after statement #1
	; {print "start #2"; if (x > 1) a()} print "after #2";
	start statement #2
	abort from a()
	; {print "start #3"; if (x > 1) quit "quit from 3rd statement"}
	start #3
	quit from 3rd statement

    The ABORT from within the a() function returned control to
    the interactive level.

    The QUIT (after the if (x > 1) ...) will cause calc to exit
    because it was given at the interactive prompt level.

    =-=

    Also see the help topic:

	statement   flow control and declaration statements
	usage	    how to invoke the calc command and calc -options

## Copyright (C) 1999-2006,2018,2021  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
##
## Under source code control:	1991/07/21 04:37:17
## File existed as early as:	1991
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/
