BC(1)									 BC(1)

NAME
       bc - arbitrary-precision arithmetic language

SYNOPSIS
       bc [ -cdls ] [ file ...	]

DESCRIPTION
       Bc is an interactive processor for a language that resembles C but pro‐
       vides 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 -d option enables debugging output.	The -l option stands  for  the
       name  of an arbitrary precision math library.  The -s option 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 vari‐
       able  simultaneously.   All variables are global to the program.	 Auto‐
       matic variables are pushed down during function calls.  In  a  declara‐
       tion  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  automati‐
       cally,  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
       /sys/lib/bclib mathematical library

SOURCE
       /sys/src/cmd/bc.y

SEE ALSO
       dc(1), hoc(1)

BUGS
       No or operators.

       A statement must have all three

       A is interpreted when read, not when executed.

									 BC(1)

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