bc

BC(1)                       General Commands Manual                      BC(1)



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.

       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
       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
       dc(1), hoc(1)

BUGS
       No or operators.

       A statement must have all three

       A is interpreted when read, not when executed.



                                                                         BC(1)