bcplan9 - Online in the Cloud

PROGRAM:

NAME

bc - arbitrary-precision arithmetic language

SYNOPSIS

bc [ -c ] [ -l ] [ -s ] [ 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 -l argument stands for the
name of an arbitrary precision math library. The -s argument suppresses the automatic
display of calculation 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
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 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)

Use bcplan9 online using onworks.net services