statement

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Statements

	Statements are very much like C statements.  Most statements act
	identically to those in C, but there are minor differences and
	some additions.  The following is a list of the statement types,
	with explanation of the non-C statements.  In this list, upper
	case words identify the keywords which are actually in lower case.
	Statements are generally terminated with semicolons, except if the
	statement is the compound one formed by matching braces.  Various
	expressions are optional and may be omitted (as in RETURN).


	NOTE: Calc commands are in lower case.   UPPER case is used below
	      for emphasis only, and should be considered in lower case.


	IF (expr) statement
	IF (expr) statement ELSE statement
	FOR (optionalexpr ; optionalexpr ; optionalexpr) statement
	WHILE (expr) statement
	DO statement WHILE (expr)
	CONTINUE
	BREAK
	GOTO label
		These all work like in normal C.

	RETURN optionalexpr
		This returns a value from a function.  Functions always
		have a return value, even if this statement is not used.
		If no return statement is executed, or if no expression
		is specified in the return statement, then the return
		value from the function is the null type.

	SWITCH (expr) { caseclauses }
		Switch statements work similarly to C, except for the
		following.  A switch can be done on any type of value,
		and the case statements can be of any type of values.
		The case statements can also be expressions calculated
		at runtime.  The calculator compares the switch value
		with each case statement in the order specified, and
		selects the first case which matches.  The default case
		is the exception, and only matches once all other cases
		have been tested.

	{ statements }
		This is a normal list of statements, each one ended by
		a semicolon.  Unlike the C language, no declarations are
		permitted within an inner-level compound statement.
		Declarations are only permitted at the beginning of a
		function definition, or at the beginning of an expression
		sequence.

	MAT variable [dimension] [dimension] ...
	MAT variable [dimension, dimension, ...]
	MAT variable [] = { value, ... }
		This creates a matrix variable with the specified dimensions.
		Matrices can have from 1 to 4 dimensions.  When specifying
		multiple dimensions, you can use either the standard C syntax,
		or else you can use commas for separating the dimensions.
		For example, the following two statements are equivalent,
		and so will create the same two dimensional matrix:

			mat foo[3][6];
			mat foo[3,6];

		By default, each dimension is indexed starting at zero,
		as in normal C, and contains the specified number of
		elements.  However, this can be changed if a colon is
		used to separate two values.  If this is done, then the
		two values become the lower and upper bounds for indexing.
		This is convenient, for example, to create matrices whose
		first row and column begin at 1.  Examples of matrix
		definitions are:

			mat x[3]	one dimension, bounds are 0-2
			mat foo[4][5]	two dimensions, bounds are 0-3 and 0-4
			mat a[-7:7]	one dimension, bounds are (-7)-7
			mat s[1:9,1:9]	two dimensions, bounds are 1-9 and 1-9

		Note that the MAT statement is not a declaration, but is
		executed at runtime.  Within a function, the specified
		variable must already be defined, and is just converted to
		a matrix of the specified size, and all elements are set
		to the value of zero.  For convenience, at the top level
		command level, the MAT command automatically defines a
		global variable of the specified name if necessary.

		Since the MAT statement is executed, the bounds on the
		matrix can be full expressions, and so matrices can be
		dynamically allocated.  For example:

			size = 20;
			mat data[size*2];

		allocates a matrix which can be indexed from 0 to 39.

		Initial values for the elements of a matrix can be specified
		by following the bounds information with an equals sign and
		then a list of values enclosed in a pair of braces.  Even if
		the matrix has more than one dimension, the elements must be
		specified as a linear list.  If too few values are specified,
		the remaining values are set to zero.  If too many values are
		specified, a runtime error will result.  Examples of some
		initializations are:

			mat table1[5] = {77, 44, 22};
			mat table2[2,2] = {1, 2, 3, 4};

		When an initialization is done, the bounds of the matrix
		can optionally be left out of the square brackets, and the
		correct bounds (zero based) will be set.  This can only be
		done for one-dimensional matrices.  An example of this is:

			mat fred[] = {99, 98, 97};

		The MAT statement can also be used in declarations to set
		variables as being matrices from the beginning.  For example:

			local mat temp[5];
			static mat strtable[] = {"hi", "there", "folks");

	OBJ type { elementnames } optionalvariables
	OBJ type variable

		These create a new object type, or create one or more
		variables of the specified type.  For this calculator,
		an object is just a structure which is implicitly acted
		on by user defined routines.  The user defined routines
		implement common operations for the object, such as plus
		and minus, multiply and divide, comparison and printing.
		The calculator will automatically call these routines in
		order to perform many operations.
	
		To create an object type, the data elements used in
		implementing the object are specified within a pair
		of braces, separated with commas.  For example, to
		define an object will will represent points in 3-space,
		whose elements are the three coordinate values, the
		following could be used:
	
			obj point {x, y, z};
	
		This defines an object type called point, whose elements
		have the names x, y, and z.  The elements are accessed
		similarly to structure element accesses, by using a period.
		For example, given a variable 'v' which is a point object,
		the three coordinates of the point can be referenced by:

			v.x
			v.y
			v.z

		A particular object type can only be defined once, and
		is global throughout all functions.  However, different
		object types can be used at the same time.

		In order to create variables of an object type, they
		can either be named after the right brace of the object
		creation statement, or else can be defined later with
		another obj statement.  To create two points using the
		second (and most common) method, the following is used:

			obj point p1, p2;	

		This statement is executed, and is not a declaration.
		Thus within a function, the variables p1 and p2 must have
		been previously defined, and are just changed to be the
		new object type.  For convenience, at the top level command
		level, object variables are automatically defined as being
		global when necessary.

		Initial values for an object can be specified by following
		the variable name by an equals sign and a list of values
		enclosed in a pair of braces.  For example:

			obj point pt = {5, 6};

		The OBJ statement can also be used in declarations to set
		variables as being objects from the beginning.  If multiple
		variables are specified, then each one is defined as the
		specified object type.  Examples of declarations are:

			local obj point temp1;
			static obj point temp2 = {4, 3};
			global obj point p1, p2, p3;

	EXIT string
	QUIT string

		This command is used in two cases.  At the top command
		line level, quit will exit from the calculator.  This
		is the normal way to leave the calculator.  In any other
		use, quit will abort 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.

		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 (n < 0)
					quit "Negative argument";
				...
			}

		Exit is an alias for quit.


	PRINT exprs

		For interactive expression evaluation, the values of all
		typed-in expressions are automatically displayed to the
		user.  However, within a function or loop, the printing of
		results must be done explicitly.  This can be done using
		the 'printf' or 'fprintf' functions, as in standard C, or
		else by using the built-in 'print' statement.  The advantage
		of the print statement is that a format string is not needed.
		Instead, the given values are simply printed with zero or one
		spaces between each value.

		Print accepts a list of expressions, separated either by
		commas or colons.  Each expression is evaluated in order
		and printed, with no other output, except for the following
		special cases.  The comma which separates expressions prints
		a single space, and a newline is printed after the last
		expression unless the statement ends with a colon.  As
		examples:

			print 3, 4;		prints "3 4" and newline.
			print 5:;		prints "5" with no newline.
			print 'a' : 'b' , 'c';	prints "ab c" and newline.
			print;			prints a newline.

		For numeric values, the format of the number depends on the
		current "mode" configuration parameter.  The initial mode
		is to print real numbers, but it can be changed to other
		modes such as exponential, decimal fractions, or hex.

		If a matrix or list is printed, then the elements contained
		within the matrix or list will also be printed, up to the
		maximum number specified by the "maxprint" configuration
		parameter.  If an element is also a matrix or a list, then
		their values are not recursively printed.  Objects are printed
		using their user-defined routine.  Printing a file value
		prints the name of the file that was opened.


	SHOW item

		This command displays some information.
		The following is a list of the various items:

			builtins	built in functions
			globals		global variables
			functions	user-defined functions
			objfuncs	possible object functions
			memory		memory usage

		Singular forms of item may also be used.  The following 
		statement are the same:

			show builtins
			show builtin
	

	Also see the help topic:

		command         top level commands