date and time created 91/01/17 18:23:46 by bostic

[unix-history] / usr / src / usr.bin / bc / bc.1

.\" Copyright (c) 1990 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"     @(#)bc.1	6.6 (Berkeley) %G%
.\"
.Dd 
.Dt BC 1
.Os ATT 7th
.Sh NAME
.Nm bc
.Nd arbitrary-precision arithmetic language and calculator
.Sh SYNOPSIS
.Nm bc
.Op Fl c
.Op Fl l
.Ar
.Sh DESCRIPTION
.Nm Bc
is an interactive processor for a language which resembles
C but provides unlimited precision arithmetic.
It takes input from any files given, then reads
the standard input.
The
.Tp Fl l
allow specification
of an arbitrary precision math library.
.Tp Fl c
.Nm Bc
is actually a preprocessor for
.Ar dc 1 ,
which it invokes automatically, unless the
.Fl c
compile only.
option is present.
In this case the
.Ar dc
input is sent to the standard output instead.
.Tp 
.Pp
The syntax for
.Nm bc
programs is as follows;
L means letter a-z,
E means expression, S means statement.
.Pp
Comments
.Ds I
are enclosed in /* and */.
.De
.Pp
Names
.Ds I
simple variables: L
array elements: L [ E ]
The words `ibase', `obase', and `scale'
.De
.Pp
Other operands
.Ds I
arbitrarily long numbers with optional sign and decimal point.
\&( E \&)
sqrt ( E )
length ( E )	number of significant decimal digits
scale ( E )	number of digits right of decimal point
L ( E , ... , E )
.De
.Pp
Operators
.Ds I
\&+  \-  *  /  %  ^ (% is remainder; ^ is power)
\&++   \-\-         (prefix and postfix; apply to names)
\&==  <=  >=  !=  <  >
\&=  +=  \-=  *=  /=  %=  ^=
.De
.Pp
Statements
.Ds I
E
{ S ; ... ; S }
if ( E ) S
while ( E ) S
for ( E ; E ; E ) S
null statement
break
quit
.De
.Pp
Function definitions
.Ds I
define L ( L ,..., L ) {
	auto L, ... , L
	S; ... S
	return ( E )
}
.De
.Pp
Functions in
.Fl l
math library
.Dw j(n,x)
.Dp s(x)
sine
.Dp c(x)
cosine
.Dp e(x)
exponential
.Dp l(x)
log
.Dp a(x)
arctangent
.Dp j(n,x)
Bessel function
.Dp
.Pp
All function arguments are passed by value.
.Pp
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
.Ar scale
influences the number of digits to be retained on arithmetic
operations in the manner of
.Xr dc 1 .
Assignments to
.Ar ibase
or
.Ar 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.
`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.
.Pp
For example
.Pp
.Ds I
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
	}
}
.De
.Pp
.fi
defines a function to compute an approximate value of
the exponential function and
.Pp
.Dl for(i=1; i<=10; i++) e(i)
.Pp
prints approximate values of the exponential function of
the first ten integers.
.Sh FILES
.\" /usr/lib/lib.b	mathematical library
.Dw Dc(1)
.Di L
.Dp Pa dc(1)	desk calculator proper
.Dp
.Sh SEE ALSO
.Xr dc 1
.br
L. L. Cherry and R. Morris,
.Em BC \- An arbitrary precision desk-calculator language
.Sh HISTORY
The
.Nm bc
command appeared in Version 7 AT&T UNIX.
.Sh BUGS
No &&, \(or\\(or, or ! operators.
.br
.Ql For
statement must have all three E's.
.br
.Ql Quit
is interpreted when read, not when executed.