BC(1)
NAME
bc − arbitrary-precision arithmetic language
USAGE
bc [ −c ] [ −l name ] [ file ... ]
DESCRIPTION
Bc is an interactive processor for a language that resembles C, but provides unlimited precision arithmetic. It takes input from any file given, then reads the standard input.
Bc is actually a preprocessor for dc (1), which it usually invokes automatically.
PROGRAM SYNTAX
The syntax for bc programs is shown below (L = letters a−z, E = expression, S = statement).
The value of a statement that is an expression is printed unless the main operator is an assignment. Either semicolons or newlines may separate statements. As in dc (1), an assignment to scale influences the number of digits to be retained on arithmetic operations. An assignment to ibase or obase sets 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. “Auto” variables are pushed down during function calls. When using arrays as function arguments or defining them as automatic variables, empty square brackets must follow the array name.
Comments
Enclosed in /∗ and ∗/.
Names
Simple variables: L
Array elements: L [ E ]
The words ibase, obase, and scale
Other Operands
Arbitrarily long numbers with optional signs and decimal points
( E )
sqrt ( E )
length ( E )Number of significant decimal digits
scale ( E )Number of digits right of decimal point
L ( E , ... , E )
Operators
+ − ∗ / % ^ (% is remainder; ^ is power)
++ − −(Prefix and postfix; apply to names)
== <= >= != < >
= =+ =− =∗ =/ =% =^
Statements
E
{ S ; ... ; S }
if ( E ) S
while ( E ) S
for ( E ; E ; E ) S
null statement
break
quit
Function Definitions
define L ( L ,..., L ) {
auto L, ... , L
S; ... S
return ( E )
}
Functions in 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.
OPTIONS
−c Compile only. Send the input of dc (1) to standard output.
−l name Include /usr/lib/lib.b as the arbitrary precision math library to be used.
EXAMPLE
scale = 20
define e(x){
auto a, b, c, i, s
a = 1
b = 1
s = 1
for(i=1; 1==1; i++){
a = a∗x
b = b∗i
c = a/b
if(c == 0) return(s)
s = s+c
}
}
defines a function to compute an approximate value of the exponential function and
for(i=1; i<=10; i++) e(i)
prints approximate values of the exponential function for the first ten integers.
CAUTIONS
The double ampersand (&&) and double pipe (||) characters are not yet valid operators for use with bc.
A for statement must have all three E’s.
Quit is interpreted when read, but not when executed.
FILES
/usr/lib/lib.b mathematical library
/usr/bin/dc desk calculator proper