Subversion Repositories planix.SVN

.TH BC 1 

.SH NAME

bc \- arbitrary-precision arithmetic language

.SH SYNOPSIS

.B bc

[

.B -cdls

]

[

.I file ...

]

.SH DESCRIPTION

.I Bc

is an interactive processor for a language that resembles

C but provides arithmetic on numbers of arbitrary length with up

to 100 digits right of the decimal point.

It takes input from any files given, then reads

the standard input.

.PP

The

.B -d

option enables debugging output.

The

.B -l

option stands for the name

of an arbitrary precision math library.

The

.B -s

option suppresses the automatic display

of calculation results; all output is via the

.B print

command.

.PP

The following syntax for 

.I bc

programs is like that of C;

.I L

means letter

.BR a - z ,

.I E

means expression,

.I S

means statement.

.TF length(E)

.TP

Lexical

.RS

.HP

comments are enclosed in

.B /* */

.HP

newlines end statements

.RE

.TP

Names

.IP

simple variables:

.I L

.br

array elements:

.IB L [ E ]

.br

The words

.BR ibase ,

.BR obase ,

and

.B scale

.TP

Other operands

.IP

arbitrarily long numbers with optional sign and decimal point.

.RS

.TP

.BI ( E )

.TP

.BI sqrt( E )

.TP

.BI length( E )

number of significant decimal digits

.TP

.BI scale( E )

number of digits right of decimal point

.TP

.IB L ( E , ... ,\fIE\fP)

function call

.RE

.TP

Operators

.RS

.HP

.B "+  -  *  /  %  ^\ "

.RB ( %

is remainder;

.B ^

is power)

.HP

.B "++  --\ "

.TP

.B "==  <=  >=  !=  <  >"

.TP

.B "=  +=  -=  *=  /=  %=  ^="

.RE

.TP

Statements

.RS

.br

.I E

.br

.B {

.I S

.B ;

\&...

.B ;

.I S

.B }

.br

.B "print"

.I E

.br

.B "if ("

.I E

.B )

.I S

.br

.B "while ("

.I E

.B )

.I S

.br

.B "for ("

.I E

.B ;

.I E

.B ;

.I E

.B ")"

.I  S

.br

null statement

.br

.B break

.br

.B quit

.br

\fL"\fRtext\fL"\fR

.RE

.TP

Function definitions

.RS

.br

.B define

.I L

.B (

.I L

.B ,

\&...

.B ,

.I L

.B ){

.PD0

.br

.B auto

.I L

.B ,

\&...

.B ,

.I L

.br

.I S

.B ;

\&...

.B ;

.I  S

.br

.B return

.I E

.LP

.B }

.RE

.TP

Functions in 

.B -l

math library

.RS

.TP

.BI s( x )

sine

.TP

.BI c( x )

cosine

.TP

.BI e( x )

exponential

.TP

.BI l( x )

log

.TP

.BI a( x )

arctangent

.TP

.BI j( "n, x" )

Bessel function

.RE

.PP

.DT

All function arguments are passed by value.

.PD

.PP

The value of an expression at the top level is printed

unless the main operator is an assignment or the

.B -s

command line argument is given.

Text in quotes, which may include newlines, is always printed.

Either semicolons or newlines may separate statements.

Assignment to

.B scale

influences the number of digits to be retained on arithmetic

operations in the manner of

.IR dc (1).

Assignments to

.B ibase

or

.B obase

set the input and output number radix respectively.

.PP

The same letter may be used as an array, a function,

and a simple variable simultaneously.

All variables are global to the program.

Automatic variables are pushed down during function calls.

In a declaration of an array as a function argument

or automatic variable

empty square brackets must follow the array name.

.PP

.I Bc

is actually a preprocessor for

.IR dc (1),

which it invokes automatically, unless the

.B -c

(compile only)

option is present.

In this case the

.I dc

input is sent to the standard output instead.

.SH EXAMPLE

Define a function to compute an approximate value of

the exponential.

Use it to print 10 values.

(The exponential function in the library gives better answers.)

.PP

.EX

scale = 20

define e(x) {

	auto a, b, c, i, s

	a = 1

	b = 1

	s = 1

	for(i=1; 1; i++) {

		a *= x

		b *= i

		c = a/b

		if(c == 0) return s

		s += c

	}

}

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

.EE

.SH FILES

.B /sys/lib/bclib

mathematical library

.SH SOURCE

.B /sys/src/cmd/bc.y

.SH "SEE ALSO"

.IR dc (1), 

.IR hoc (1)

.SH BUGS

No

.LR && ,

.LR || ,

or

.L !

operators.

.PP

A

.L for

statement must have all three

.LR E s.

.PP

A

.L quit

is interpreted when read, not when executed.