ICALC(1)						      General Commands Manual							  ICALC(1)

NAME

       icalc - interactive calculator

SYNOPSIS

       icalc [ file ]

DESCRIPTION

       Icalc  is  a algebraic calculator designed primarily for interactive use.  Each formula definition file is read and compiled.  The standard
       input is then read, expressions are evaluated and results are sent to the standard output.  If a newline  is  escaped  using  a	backslash,
       input is continued on the next line.

       An expression contains real numbers, variable names, function calls, and the following operators:

	    +  -  *  /	^

       Operators  are  evaluated left to right, except '^', which is right associative.  Exponentiation has the highest precedence; multiplication
       and division are evaluated before addition and subtraction.  Expressions can be grouped with parentheses.  Each result is assigned  a  num-
       ber,  which  can  be  used in future expressions.  For example, the expression ($3*10) is the result of the third calculation multiplied by
       ten.  A dollar sign by itself may be used for the previous result.  All values are double precision real.

       In addition, variables and functions can be defined by the user.  A variable definition has the form:

	    var = expression ;

       Any instance of the variable in an expression will be replaced with its definition.  A function definition has the form:

	    func(a1, a2, ..) = expression ;

       The expression can contain instances of the function arguments as well as other variables and functions.  Function names can be	passed	as
       arguments.  Recursive functions can be defined using calls to the defined function or other functions calling the defined function.

       To  define a constant expression, simply replace the equals sign ('=') with a colon (':') in a definition.  Constant expressions are evalu-
       ated only once, the first time they are used.  This avoids repeated evaluation of expressions whose values never change.  Ideally,  a  con-
       stant  expression contains only numbers and references to previously defined constant expressions and functions.  Constant function defini-
       tions are are replaced by their value in any expression that uses them with constant arguments.	All  predefined  functions  and  variables
       have  the  constant attribute.  Thus, "sin(PI/4)" in an expression would be immediately replaced by ".707108" unless sin() or PI were rede-
       fined by the user.  (Note that redefining constant expressions is not a recommended practice!)

       A variable or function's definition can be displayed with the '?'  command:

	    ? name

       If no name is given, all definitions are printed.  The '>' command writes definitions to a file:

	    > file

       Similarly, the '<' command loads definitions.

       The following library of predefined functions and variables is provided:

       PI	 the ratio of a circle's circumference to its diameter.

       if(cond, then, else)
		 if cond is greater than zero, then is evaluated, otherwise else is evaluated.	This function is necessary for	recursive  defini-
		 tions.

       select(N, a1, a2, ..)
		 return  aN (N is rounded to the nearest integer).  This function provides array capabilities.	If N is zero, the number of avail-
		 able arguments is returned.

       rand(x)	 compute a random number between 0 and 1 based on x.

       floor(x)  return largest integer not greater than x.

       ceil(x)	 return smallest integer not less than x.

       sqrt(x)	 return square root of x.

       exp(x)	 compute e to the power of x (e approx = 2.718281828).

       log(x)	 compute the logarithm of x to the base e.

       log10(x)  compute the logarithm of x to the base 10.

       sin(x), cos(x), tan(x)
		 trigonometric functions.

       asin(x), acos(x), atan(x)
		 inverse trigonometric functions.

       atan2(y, x)
		 inverse tangent of y/x (range -pi to pi).

AUTHOR

       Greg Ward

SEE ALSO

       ev(1), rcalc(1), tabfunc(1)

RADIANCE
							      2/3/95								  ICALC(1)