BC(1plan9) | BC(1plan9) |

# 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.

comments are enclosed in **/* */**

newlines end statements

- simple variables:
*L*

array elements:*L***[***E***]**

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*)- function call

**+ - * / % ^ ** (**%** is remainder; **^** is
power)

**++ -- **

**== <= >= != < >****= += -= *= /= %= ^=**

*E*

**{**

*S*

**;**...

**;**

*S*

**}**

*E*

**if (**

*E*

**)**

*S*

**while (**

*E*

**)**

*S*

**for (**

*E*

**;**

*E*

**;**

*E*

**)**

*S*

null statement

**break**

**quit**

"text"

**define**

*L*

**(**

*L*

**,**...

**,**

*L*

**){**

**auto**

*L*

**,**...

**,**

*L*

*S*

**;**...

**;**

*S*

**return**

*E*

**}**

- Functions in
**-l**math library

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¶

**/lib/bclib** mathematical library

# SOURCE¶

**/src/cmd/bc.y**

# SEE ALSO¶

# BUGS¶

No or operators.

A statement must have all three

A is interpreted when read, not when executed.