Radiance icalc program

ICALC(1)                                                              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 asso-
       ciative.  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 number,
       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 evaluated
       only once, the first time they are used.  This avoids repeated  evalua-
       tion  of  expressions  whose  values never change.  Ideally, a constant
       expression contains only numbers and references to  previously  defined
       constant  expressions and functions.  Constant function definitions are
       are replaced by their value in any expression that uses them with  con-
       stant  arguments.  All predefined functions and variables have the con-
       stant attribute.  Thus, "sin(PI/4)" in an expression would  be  immedi-
       ately  replaced  by  ".707108" unless sin() or PI were redefined by the
       user.  (Note that redefining constant expressions is not a  recommended
       practice!)

       A variable or function's definition can be displayed with the '?'  com-
       mand:

            ? 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 pro-
       vided:

       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
                 definitions.

       select(N, a1, a2, ..)
                 return aN (N is rounded to the nearest integer).  This  func-
                 tion  provides  array capabilities.  If N is zero, the number
                 of available 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)