
NAME
 
bc – arbitraryprecision 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 az, 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)

FILES
SOURCE
SEE ALSO
BUGS
 
No &&, , or ! operators.
A for statement must have all three Es.
A quit is interpreted when read, not when executed.


