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Manual page for BC(1)

bc - arbitrary-precision arithmetic language

SYNOPSIS

bc [ -c ] [ -l ] [ filename...]

DESCRIPTION

bc is an interactive processor for a language which resembles C but provides unlimited precision arithmetic. bc takes input from any files given, then reads the standard input.

OPTIONS

-c: Compile only. bc is actually a preprocessor for dc.1 which it invokes automatically, unless the -c (compile only) option is present. In this case the dc input is sent to the standard output instead.
-l: Is the name of an arbitrary precision math library.

USAGE

Comments

Enclosed in /* and */.

Names

Simple variables: l, where, l is a lower-case letter.
Array elements: l[expression], where, expression is a legal bc expression.
The words ibase, obase, and scale.

Other Operands

Arbitrarily long numbers with optional sign and decimal point.

(expression)
sqrt (expression)
length (expression): Number of significant decimal digits
scale (expression): Number of digits right of decimal point
l(expression,: ..., expression)

Operators

+ - * / % ^: (% is remainder; ^ is exponent)
++ --: (prefix and postfix; apply to names)
== <= >= != < >
= += -= *= /= %= ^=

Statements

expression
{statement; ...; statement}: where, statement is a legal bc statement.
if (expression)statement
while ( expression ) statement
for ( expression ; expression ; expression ) statement
null statement
break
quit

Function Definitions

define: l ( l,...,l ) {
auto l ,..., l
statement ;... statement
return ( expression ) }

Functions in -l Math Library

s(x): sine
c(x): cosine
e(x): exponential
l(x): log
a(x): arctangent
j(n,x): Bessel function

All function arguments are passed by value.

The value of a statement that is an expression is printed unless the main operator is an assignment. Either semicolons or newlines may separate statements. Assignment to scale influences the number of digits to be retained on arithmetic operations in the manner of dc.1 Assignments to ibase or obase set the input and output number radix respectively.

The same letter may be used as an array, a function, and a simple variable simultaneously. All variables are global to the program. `Auto' variables are pushed down during function calls. When using arrays as function arguments or defining them as automatic variables empty square brackets must follow the array name.

EXAMPLES

Define a function to compute an approximate value of the exponential function:

scale = 20
define
e(x){
	auto a, b, c, i, s
	a = 1
	b = 1
	s = 1
	for(i=1; 1==1; i++){
		a = a*x
		b = b*i
		c = a/b
		if(c == 0) return(s)
		s = s+c
	}
}

Print approximate values of the exponential function of the first ten integers:

	for(i=1; i<=10; i++) e(i)

FILES

/usr/lib/lib.b: mathematical library
dc.1: desk calculator proper

BUGS

for statement must have all three expression's.
quit is interpreted when read, not when executed.