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.\" RCSid "$Id: icalc.1,v 1.1 2004/01/01 19:31:45 greg Exp $"
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.TH ICALC 1 2/3/95 RADIANCE
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.SH NAME
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icalc - interactive calculator
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.SH SYNOPSIS
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.B icalc
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[
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.B file
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]
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.SH DESCRIPTION
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.I Icalc
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is a algebraic calculator designed primarily for
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interactive use.
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Each formula definition
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.I file
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is read and compiled.
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The standard input is then read, expressions are evaluated
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and results are sent to the standard output.
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If a newline is escaped using a backslash, input is continued
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on the next line.
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.PP
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An expression contains real numbers, variable names, function calls,
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and the following operators:
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.PP
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+ - * / ^
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.PP
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Operators are evaluated left to right, except '^',
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which is right associative.
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Exponentiation has the highest precedence; multiplication and
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division are evaluated before addition and subtraction.
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Expressions can be grouped with parentheses.
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Each result is assigned a number, which can be used in future expressions.
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For example, the expression ($3*10) is the result of the
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third calculation multiplied by ten.
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A dollar sign by itself may be used for the previous result.
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All values are double precision real.
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.PP
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In addition, variables and functions can be defined by the
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user.
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A variable definition has the form:
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.PP
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var = expression ;
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.PP
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Any instance of the variable in an expression will be replaced
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with its definition.
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A function definition has the form:
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.PP
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func(a1, a2, ..) = expression ;
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.PP
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The expression can contain instances of the function arguments
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as well as other variables and functions.
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Function names can be passed as arguments.
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Recursive functions can be defined using calls to the defined
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function or other functions calling the defined function.
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.PP
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To define a constant expression, simply replace the equals sign ('=')
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with a colon (':') in a definition.
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Constant expressions are evaluated only once, the first time they are used.
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This avoids repeated evaluation of expressions whose values never change.
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Ideally, a constant expression contains only numbers and references
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to previously defined constant expressions and functions.
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Constant function definitions are are
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replaced by their value in any expression that uses them with constant
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arguments.
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All predefined functions and variables have the constant attribute.
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Thus, "sin(PI/4)" in an expression would be immediately replaced by ".707108"
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unless sin() or PI were redefined by the user.
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(Note that redefining constant expressions is not a recommended practice!)\
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.PP
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A variable or function's definition can be displayed with the '?'
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command:
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.PP
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? name
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.PP
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If no name is given, all definitions are printed.
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The '>' command writes definitions to a file:
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.PP
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> file
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.PP
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Similarly, the '<' command loads definitions.
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.PP
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The following library of predefined functions and variables is provided:
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.TP 10n
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.BR PI
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the ratio of a circle's circumference to its diameter.
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.TP
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.BR "if(cond, then, else)"
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if cond is greater than zero,
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then is evaluated, otherwise else is evaluated.
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This function is necessary for recursive definitions.
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.TP
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.BR "select(N, a1, a2, ..)"
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return aN (N is rounded to the nearest integer).
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This function provides array capabilities.
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If
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.I N
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is zero, the number of available arguments is returned.
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.TP
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.BR "rand(x)"
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compute a random number between 0 and 1 based on x.
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.TP
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.BR "floor(x)"
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return largest integer not greater than x.
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.TP
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.BR "ceil(x)"
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return smallest integer not less than x.
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.TP
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.BR "sqrt(x)"
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return square root of x.
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.TP
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.BR "exp(x)"
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compute e to the power of x (e approx = 2.718281828).
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.TP
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.BR "log(x)"
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compute the logarithm of x to the base e.
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.TP
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.BR "log10(x)"
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compute the logarithm of x to the base 10.
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.TP
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.BR "sin(x), cos(x), tan(x)"
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trigonometric functions.
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.TP
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.BR "asin(x), acos(x), atan(x)"
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inverse trigonometric functions.
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.TP
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.BR "atan2(y, x)"
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inverse tangent of y/x (range \-pi to pi).
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.SH AUTHOR
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Greg Ward
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.SH "SEE ALSO"
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ev(1), rcalc(1), tabfunc(1)
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