290 lines
3.7 KiB
Text
290 lines
3.7 KiB
Text
.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.
|