4.4BSD/usr/src/contrib/calc-1.26.4/help/statement
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, ...]
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.
OBJ type { elementnames } optionalvariables
OBJ type variables
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.
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
Also see the help topic:
command top level commands