plan9 man page for bc

BC(1)							      General Commands Manual							     BC(1)

NAME
       bc - arbitrary-precision arithmetic language

SYNOPSIS
       bc [ -c ] [ -l ] [ 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 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.  Text in quotes, which may  include  new-
       lines,  is also 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  respec-
       tively.

       The same letter may be used as an array, a function, and a simple variable simultaneously.  All variables are global to the program.  Auto-
       matic 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
       /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)