bc(1)

bc -- arbitrary-precision arithmetic language

Synopsis

   bc [-c] [-l] [file . . .]

Description

bc is an interactive processor for a language that resembles C but provides unlimited precision arithmetic. It takes input from any files given, then reads the standard input. bc is actually a preprocessor for the desk calculator program dc, which it invokes automatically unless the -c option is present. In this case the dc input is sent to the standard output instead. The options are as follows:

-c: Compile only. The output is sent to the standard output.
-l: Argument stands for the name of an arbitrary precision math library.

The syntax for bc programs is as follows: L means letter a-z, E means expression, S means statement.

Comments

enclosed in / and /

Names

simple variables:: L
array elements:: L [E]
keywords:: the words ibase, obase, and scale

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 )

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 -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 a statement that is an expression is printed unless the main operator is an assignment. Either semicolons or new-lines may separate statements. Assignment to scale influences the number of digits to be retained on arithmetic operations in the manner of dc. 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. 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.

Examples

   scale = 20
   define e(x){
   	auto a, b, c, i, s
   	a = 1
   	b = 1
   	s = 1
   	for(i=1; 1==1; i++){
   		a = ax
   		b = bi
   		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 of the first ten integers.

Files

/usr/lib/lib.b: mathematical library
/usr/bin/dc: desk calculator proper

References

dc(1)

Notices

The bc command does not recognize the logical operators ``&&'' and ``||''.

The for statement must have all three expressions (E's).

The quit statement is interpreted when read, not when executed.

For certain operations, the value of scale might be calculated to be larger than the current specified scale value. When you set scale to a large value, take this into account when performing operations that could overflow the specified scale value.