bc(1)                                                                 bc(1)




 NAME    [Toc]    [Back]
      bc - arbitrary-precision arithmetic language

 SYNOPSIS    [Toc]    [Back]
      bc [-c] [-l] [file ...]

 DESCRIPTION    [Toc]    [Back]
      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.

    Options:
      bc recognizes the following command-line options:

           -c        Compile only.  bc is actually a preprocessor for dc
                     which bc invokes automatically (see dc(1)).  Specifying
                     -c prevents invoking dc, and sends the dc input to
                     standard output.

           -l        causes an arbitrary-precision math library to be
                     predefined.  As a side effect, the scale factor is set.

    Program Syntax:
      L    a single letter in the range a through z;
      E    expression;
      S    statement;
      R    relational expression.

    Comments:
      Comments are enclosed in /* and */.

    Names:
      Names include:

           simple variables: L
           array elements: L [ E ]
           The words ibase,obase, and scale
           stacks:   L

    Other Operands    [Toc]    [Back]
      Other operands include:

           Arbitrarily long numbers with optional sign and decimal point.

           ( E )

           sqrt ( E )

           length ( E )        number of significant decimal digits





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 bc(1)                                                                 bc(1)




           scale ( E )         number of digits right of decimal point

           L ( E , ... , E )

           Strings of ASCII characters enclosed in quotes (").

    Arithmetic Operators:
      Arithmetic operators yield an E as a result and include:

           +  -  *  /  %  ^                        (% is remainder (not mod,
                                                   see below); ^ is power).

           ++  --                                  (prefix and append; apply
                                                   to names)

           =  +=  -=  *=  /=  %=  ^=

    Relational Operators    [Toc]    [Back]
      Relational operators yield an R when used as E op E:

           ==  <=  >=  !=  <  >

    Statements    [Toc]    [Back]
      E
      { S ; ... ; S }
      if ( R ) S
      while ( R ) S
      for ( E ; R ; E ) S
      null statement
      break
      quit

    Function Definitions:
      define L ( L ,..., L ) {
           auto L, ... , L
           S; ... S
           return ( E )
      }

    Functions in -l Math Library:
      Functions in the -l math library include:

           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.  Trigonometric angles are
      in radians where 2 pi radians = 360 degrees.



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 bc(1)                                                                 bc(1)




      The value of a statement that is an expression is printed unless the
      main operator is an assignment.  No operators are defined for strings,
      but the string is printed if it appears in a context where an
      expression result would be printed.  Either semicolons or new-lines
      can 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, again as defined by dc(1).

      The same letter can be used simultaneously as an array, a function,
      and a simple variable.  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.

      The % operator yields the remainder at the current scale, not the
      integer modulus.  Thus, at scale 1, 7 % 3 is .1 (one tenth), not 1.
      This is because (at scale 1) 7 / 3 is 2.3 with .1 as the remainder.

 EXAMPLES    [Toc]    [Back]
      Define a function to compute an approximate value of the exponential
      function:

           scale = 20
           define e(x){
                   auto a, b, c, i, s
                   a = 1
                   b = 1
                   s = 1
                   for(i=1; 1==1; i++){
                           a = a*x
                           b = b*i
                           c = a/b
                           if(c == 0) return(s)
                           s = s+c
                   }
           }

      Print approximate values of the exponential function of the first ten
      integers.

           for(i=1; i<=10; i++) e(i)

 WARNINGS    [Toc]    [Back]
      There are currently no && (AND) or || (OR) comparisons.

      The for statement must have all three expressions.

      quit is interpreted when read, not when executed.





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 bc(1)                                                                 bc(1)




      bc's parser is not robust in the face of input errors.  Some simple
      expression such as 2+2 helps get it back into phase.

      The assignment operators: =+  =-  =*  =/  =% and =^ are obsolete.  Any
      occurences of these operators cause a syntax error with the exception
      of =- which is interpreted as = followed by a unary minus.

      Neither entire arrays nor functions can be passed as function
      parameters.

 FILES    [Toc]    [Back]
      /usr/bin/dc                   desk calculator executable program
      /usr/lib/lib.b                mathematical library

 SEE ALSO    [Toc]    [Back]
      bs(1), dc(1).

      bc tutorial in Number Processing Users Guide

 STANDARDS CONFORMANCE    [Toc]    [Back]
      bc: XPG4, POSIX.2


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