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. Statements are generally terminated with semicolons or { ... }. C-like statements ----------------- { statement } { statement; ... statement } C-like flow control ------------------- if (expr) statement if (expr) statement else statement for (optionalexpr ; optionalexpr ; optionalexpr) statement while (expr) statement do statement while (expr) These all work like in normal C. IMPORTANT NOTE: When statement is of the form { ... }, the leading { must be on the same line as the if, for, while or do keyword. This works as expected: if (expr) { ... } However this WILL NOT WORK AS EXPECTED: if (expr) { ... } because calc will parse the if being terminated by an empty statement followed by a if (expr) ; { ... } In the same way, use these forms: for (optionalexpr ; optionalexpr ; optionalexpr) { ... } while (expr) { ... } do { ... while (expr); where the initial { is on the SAME LINE as the if, while, for or do. See 'help expression' for details on expressions. See 'help builtin' for details on calc builtin functions. See 'help unexpanded' for things C programmers do not expect. See also 'help todo' and 'help bugs'. C-like flow breaks ------------------ continue break goto label These all work like in normal C. See 'help expression' for details on expressions. See 'help builtin' for details on calc builtin functions. return ------ return return expr return ( expr ) 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 ------ 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. matrix ------ 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"); object ------ 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; print expressions ----------------- print expr print expr, ... expr print expr: ... expr 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. Also see the help topic: help command top level commands help expression calc expression syntax help builtin calc builtin functions help usage how to invoke the calc command and calc -options You may obtain help on individual builtin functions. For example: help asinh help round See: help builtin for a list of builtin functions. Some calc operators have their own help pages: help -> help * help . help % help // help # See also: help help ## Copyright (C) 1999-2007 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. ## ## @(#) $Revision: 30.1 $ ## @(#) $Id: statement,v 30.1 2007/03/16 11:10:42 chongo Exp $ ## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/statement,v $ ## ## Under source code control: 1991/07/21 04:37:23 ## File existed as early as: 1991 ## ## chongo /\oo/\ http://www.isthe.com/chongo/ ## Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/