don't open target for writing if we're just verifying the tapes

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

.\"	@(#)bc.1	6.2 (Berkeley) %G%
.\"
.TH BC 1 ""
.AT 3
.SH NAME
bc \- arbitrary-precision arithmetic language and calculator
.SH SYNOPSIS
.B bc
[
.B \-c
] [
.B \-l
] [ file ... ]
.SH DESCRIPTION
.I 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
.B \-l
argument stands for the name
of an arbitrary precision math library.
The syntax for 
.I bc
programs is as follows;
L means letter a-z,
E means expression, S means statement.
.HP 6
Comments
.br
are enclosed in /* and */.
.HP 6
Names
.br
simple variables: L
.br
array elements: L [ E ]
.br
The words `ibase', `obase', and `scale'
.HP 6
Other operands
.br
arbitrarily long numbers with optional sign and decimal point.
.br
( E )
.br
sqrt ( E )
.br
length ( E )	number of significant decimal digits
.br
scale ( E )	number of digits right of decimal point
.br
L ( E , ... , E )
.HP 6
Operators
.br
+  \-  *  /  %  ^
(% is remainder; ^ is power)
.br
++   \-\-         (prefix and postfix; apply to names)
.br
==  <=  >=  !=  <  >
.br
=  +=  \-=  *=  /=  %=  ^=
.br
.HP 6
Statements
.br
E
.br
{ S ; ... ; S }
.br
if ( E ) S
.br
while ( E ) S
.br
for ( E ; E ; E ) S
.br
null statement
.br
break
.br
quit
.HP 6
Function definitions
.br
define L ( L ,..., L ) {
.br
	auto L, ... , L
.br
	S; ... S
.br
	return ( E )
.br
}
.HP 6
Functions in 
.B \-l
math library
.br
s(x)	sine
.br
c(x)	cosine
.br
e(x)	exponential
.br
l(x)	log
.br
a(x)	arctangent
.br
j(n,x)	Bessel function
.PP
.DT
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
.I scale
influences the number of digits to be retained on arithmetic
operations in the manner of
.IR dc (1).
Assignments to
.I ibase
or
.I 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
.nf
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
	}
}
.PP
.fi
defines a function to compute an approximate value of
the exponential function and
.PP
.nf
	for(i=1; i<=10; i++) e(i)
.fi
.PP
prints approximate values of the exponential function of
the first ten integers.
.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 FILES
.ta \w'/usr/lib/lib.b 'u
/usr/lib/lib.b	mathematical library
.br
dc(1)	desk calculator proper
.SH "SEE ALSO"
dc(1)
.br
L. L. Cherry and R. Morris,
.I
BC \- An arbitrary precision desk-calculator language
.SH BUGS
No &&, \(or\|\(or, or ! operators.
.br
.I For
statement must have all three E's.
.br
.I Quit
is interpreted when read, not when executed.