BC(1) BC(1)
NAME
bc - arbitrary-precision arithmetic language
SYNOPSIS
bc [ -cdls ] [ file ... ]
DESCRIPTION
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 -d option enables debugging output. The -l option
stands for the name of an arbitrary precision math library.
The -s option suppresses the automatic display of calcula-
tion results; all output is via the print command.
The following syntax for bc programs is like that of C; L
means letter a-z, E means expression, S means statement.
Lexical
comments are enclosed in /* */
newlines end statements
Names
simple variables: L
array elements: L[E]
The words ibase, obase, and scale
Other operands
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)
function call
Operators
+ - * / % ^ (% is remainder; ^ is power)
++ --
== <= >= != < >
= += -= *= /= %= ^=
Statements
E
{ S ; ... ; S }
print E
if ( E ) S
while ( E ) S
for ( E ; E ; E ) S
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BC(1) BC(1)
null statement
break
quit
"text"
Function definitions
define L ( L , ... , L ){
auto L , ... , L
S ; ... ; S
return E
}
Functions in
-l math library
s(x) sine
c(x) cosine
e(x) exponential
l(x) log
a(x) arctangent
j(n, x)
Bessel function
All function arguments are passed by value.
The value of an expression at the top level is printed
unless the main operator is an assignment or the -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 scale influences the
number of digits to be retained on arithmetic operations in
the manner of dc(1). Assignments to ibase or obase set the
input and output number radix respectively.
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.
Bc is actually a preprocessor for dc(1), which it invokes
automatically, unless the -c (compile only) option is pre-
sent. In this case the dc input is sent to the standard
output instead.
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.)
scale = 20
define e(x) {
auto a, b, c, i, s
a = 1
b = 1
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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)
FILES
/sys/lib/bclib mathematical library
SOURCE
/sys/src/cmd/bc.y
SEE ALSO
dc(1), hoc(1)
BUGS
No `&&', `||', or `!' operators.
A `for' statement must have all three `E's.
A `quit' is interpreted when read, not when executed.
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