term% cat index.txt BC(1) General Commands Manual BC(1)
NAME
bc - arbitrary-precision arithmetic language
SYNOPSIS
bc [ -c ] [ -l ] [ file ... ]
DESCRIPTION
Bc is an interactive processor for a language that resembles C but pro‐
vides 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 -l argument stands for the name of an
arbitrary precision math library. 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
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. Text in quotes, which may include newlines,
is also printed. Either semicolons or newlines may separate state‐
ments. Assignment to scale influences the number of digits to be re‐
tained 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 vari‐
able simultaneously. All variables are global to the program. Auto‐
matic variables are pushed down during function calls. In a declara‐
tion 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 automati‐
cally, unless the -c (compile only) option is present. 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
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 statement must have all three
A is interpreted when read, not when executed.
BC(1)