TH BC 1
SH NAME
bc \- arbitrary-precision arithmetic language
SH SYNOPSIS
B bc
[
B -c
]
[
B -l
]
[
B -s
]
[
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.
The
B -l
argument stands for the name
of an arbitrary precision math library.
The
B -s
argument 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.
br
A
L for
statement must have all three
LR E s.
br
A
L quit
is interpreted when read, not when executed.
