BC(1)                   NetBSD General Commands Manual                   BC(1)

NAME
     bc -- arbitrary precision calculator language

SYNOPSIS
     bc [-hilqsvw] [long-options] [file ...]

DESCRIPTION
     bc is a language that supports arbitrary precision numbers with interac-
     tive execution of statements.  There are some similarities in the syntax
     to the C programming language.  A standard math library is available by
     command line option.  If requested, the math library is defined before
     processing any files.  bc starts by processing code from all the files
     listed on the command line in the order listed.  After all files have
     been processed, bc reads from the standard input.  All code is executed
     as it is read.  (If a file contains a command to halt the processor, bc
     will never read from the standard input.)

     This version of bc contains several extensions beyond traditional bc
     implementations and the POSIX draft standard.  Command line options can
     cause these extensions to print a warning or to be rejected.  This docu-
     ment describes the language accepted by this processor.  Extensions will
     be identified as such.

   OPTIONS
     -h, --help           Print the usage and exit.

     -i, --interactive    Force interactive mode.

     -l, --mathlib        Define the standard math library.

     -q, --quiet          Quiet mode.

     -s, --standard       Process exactly the POSIX bc language.

     -v, --version        Print the version number and copyright and quit.

     -w, --warn           Give warnings for extensions to POSIX bc.

   NUMBERS
     The most basic element in bc is the number.  Numbers are arbitrary preci-
     sion numbers.  This precision is both in the integer part and the frac-
     tional part.  All numbers are represented internally in decimal and all
     computation is done in decimal.  (This version of bc truncates results
     from divide and multiply operations.)  There are two attributes of num-
     bers, the length and the scale.  The length is the total number of sig-
     nificant decimal digits in a number and the scale is the total number of
     decimal digits after the decimal point.  For example:

      .000001 has a length of 6 and scale of 6.
      1935.000 has a length of 7 and a scale of 3.

   VARIABLES
     Numbers are stored in two types of variables, simple variables and
     arrays.  Both simple variables and array variables are named.  Names
     begin with a letter followed by any number of letters, digits and under-
     scores.  All letters must be lower case.  (Full alpha-numeric names are
     an extension.  In POSIX bc all names are a single lower case letter.)
     The type of variable is clear by the context because all array variable
     names will be followed by brackets ([]).

     There are four special variables, scale, ibase, obase, and last.  scale
     defines how some operations use digits after the decimal point.  The
     default value of scale is 0.  ibase and obase define the conversion base
     for input and output numbers.  The default for both input and output is
     base 10.  last (an extension) is a variable that has the value of the
     last printed number.  These will be discussed in further detail where
     appropriate.  All of these variables may have values assigned to them as
     well as used in expressions.

   COMMENTS
     Comments in bc start with the characters ``/*'' and end with the charac-
     ters ``*/''.  Comments may start anywhere and appear as a single space in
     the input.  (This causes comments to delimit other input items.  For
     example, a comment can not be found in the middle of a variable name.)
     Comments include any newlines (end of line) between the start and the end
     of the comment.

     To support the use of scripts for bc, a single line comment has been
     added as an extension.  A single line comment starts at a ``#'' character
     and continues to the next end of the line.  The end of line character is
     not part of the comment and is processed normally.

   EXPRESSIONS
     The numbers are manipulated by expressions and statements.  Since the
     language was designed to be interactive, statements and expressions are
     executed as soon as possible.  There is no ``main'' program.  Instead,
     code is executed as it is encountered.  (Functions, discussed in detail
     later, are defined when encountered.)

     A simple expression is just a constant.  bc converts constants into
     internal decimal numbers using the current input base, specified by the
     variable ibase.  (There is an exception in functions.)  The legal values
     of ibase are 2 through 36.  (Base values greater than 16 are an exten-
     sion.)  Assigning a value outside this range to ibase will result in a
     value of 2 or 36.  Input numbers may contain the characters 0-9 and A-Z.
     (Note: They must be capitals.  Lower case letters are variable names.)
     Single digit numbers always have the value of the digit regardless of the
     value of ibase.  (i.e. A = 10.)  For multi-digit numbers, bc changes all
     input digits greater or equal to ibase to the value of ibase - 1.  This
     makes the number ``ZZZ'' always be the largest 3 digit number of the
     input base.

     Full expressions are similar to many other high level languages.  Since
     there is only one kind of number, there are no rules for mixing types.
     Instead, there are rules on the scale of expressions.  Every expression
     has a scale.  This is derived from the scale of original numbers, the
     operation performed and in many cases, the value of the variable scale.
     Legal values of the variable scale are 0 to the maximum number repre-
     sentable by a C integer.

     In the following descriptions of legal expressions, ``expr'' refers to a
     complete expression and ``var'' refers to a simple or an array variable.
     A simple variable is just a name and an array variable is specified as
     name[expr].  Unless specifically mentioned the scale of the result is the
     maximum scale of the expressions involved.

     - expr           The result is the negation of the expression.

     ++ var           The variable is incremented by one and the new value is
                      the result of the expression.

     -- var           The variable is decremented by one and the new value is
                      the result of the expression.

     var ++           The result of the expression is the value of the vari-
                      able and then the variable is incremented by one.

     var --           The result of the expression is the value of the vari-
                      able and then the variable is decremented by one.

     expr + expr      The result of the expression is the sum of the two
                      expressions.

     expr - expr      The result of the expression is the difference of the
                      two expressions.

     expr * expr      The result of the expression is the product of the two
                      expressions.

     expr / expr      The result of the expression is the quotient of the two
                      expressions.  The scale of the result is the value of
                      the variable scale.

     expr % expr      The result of the expression is the remainder and it is
                      computed in the following way: To compute a%b, first a/b
                      is computed to scale digits.  That result is used to
                      compute a-(a/b)*b to the scale of the maximum of scale +
                      scale(b) and scale(a).  If scale is set to zero and both
                      expressions are integers this expression is the integer
                      remainder function.

     expr ^ expr      The result of the expression is the value of the first
                      raised to the second.  The second expression must be an
                      integer.  (If the second expression is not an integer, a
                      warning is generated and the expression is truncated to
                      get an integer value.)  The scale of the result is scale
                      if the exponent is negative.  If the exponent is posi-
                      tive, the scale of the result is the minimum of the
                      scale of the first expression times the value of the
                      exponent and the maximum of scale and the scale of the
                      first expression.  (e.g. scale(a^b) = min(scale(a)*b,
                      max( scale, scale(a))).)  It should be noted that expr^0
                      will always return the value of 1.

     ( expr )         This alters the standard precedence to force the evalua-
                      tion of the expression.

     var = expr       The variable is assigned the value of the expression.

     var <op>= expr   This is equivalent to var = var <op> expr with the
                      exception that the ``var'' part is evaluated only once.
                      This can make a difference if ``var'' is an array.

     Relational expressions are a special kind of expression that always eval-
     uate to 0 or 1, 0 if the relation is false and 1 if the relation is true.
     These may appear in any legal expression.  (POSIX bc requires that rela-
     tional expressions are used only in if, while, and for statements and
     that only one relational test may be done in them.)  The relational oper-
     ators are:

     expr1 < expr2    The result is 1 if expr1 is strictly less than expr2.

     expr1 <= expr2   The result is 1 if expr1 is less than or equal to expr2.

     expr1 > expr2    The result is 1 if expr1 is strictly greater than expr2.

     expr1 >= expr2   The result is 1 if expr1 is greater than or equal to
                      expr2.

     expr1 == expr2   The result is 1 if expr1 is equal to expr2.

     expr1 != expr2   The result is 1 if expr1 is not equal to expr2.

     Boolean operations are also legal.  (POSIX bc does NOT have boolean oper-
     ations.)  The result of all boolean operations are 0 and 1 (for false and
     true) as in relational expressions.  The boolean operators are:

     !expr            The result is 1 if expr is 0.

     expr && expr     The result is 1 if both expressions are non-zero.

     expr || expr     The result is 1 if either expression is non-zero.

     The expression precedence is as follows: (lowest to highest)

           1.   || operator, left associative

           2.   && operator, left associative

           3.   ! operator, nonassociative

           4.   Relational operators, left associative

           5.   Assignment operator, right associative

           6.   + and - operators, left associative

           7.   *, / and % operators, left associative

           8.   ^ operator, right associative

           9.   unary - operator, nonassociative

           10.  ++ and -- operators, nonassociative

     This precedence was chosen so that POSIX compliant bc programs will run
     correctly.  This will cause the use of the relational and logical opera-
     tors to have some unusual behavior when used with assignment expressions.
     Consider the expression:
           a = 3 < 5

     Most C programmers would assume this would assign the result of ``3 < 5''
     (the value 1) to the variable ``a''.  What this does in bc is assign the
     value 3 to the variable ``a'' and then compare 3 to 5.  It is best to use
     parenthesis when using relational and logical operators with the assign-
     ment operators.

     There are a few more special expressions that are provided in bc.  These
     have to do with user defined functions and standard functions.  They all
     appear as ``name (parameters)''.  See the section on functions for user
     defined functions.  The standard functions are:

     length (expression)   The value of the length function is the number of
                           significant digits in the expression.

     read ()               The read function (an extension) will read a number
                           from the standard input, regardless of where the
                           function occurs.  Beware, this can cause problems
                           with the mixing of data and program in the standard
                           input.  The best use for this function is in a pre-
                           viously written program that needs input from the
                           user, but never allows program code to be input
                           from the user.  The value of the read function is
                           the number read from the standard input using the
                           current value of the variable ibase for the conver-
                           sion base.

     scale (expression)    The value of the scale function is the number of
                           digits after the decimal point in the expression.

     sqrt (expression)     The value of the sqrt function is the square root
                           of the expression.  If the expression is negative,
                           a run time error is generated.

   STATEMENTS
     Statements (as in most algebraic languages) provide the sequencing of
     expression evaluation.  In bc statements are executed ``as soon as
     possible''.  Execution happens when a newline in encountered and there is
     one or more complete statements.  Due to this immediate execution, new-
     lines are very important in bc.  In fact, both a semicolon and a newline
     are used as statement separators.  An improperly placed newline will
     cause a syntax error.  Because newlines are statement separators, it is
     possible to hide a newline by using the backslash character.  The
     sequence ``\<nl>'', where <nl> is the newline appears to bc as whitespace
     instead of a newline.  A statement list is a series of statements sepa-
     rated by semicolons and newlines.  The following is a list of bc state-
     ments and what they do: (Things enclosed in brackets ([]) are optional
     parts of the statement.)

     expression       This statement does one of two things.  If the expres-
                      sion starts with <variable> <assignment> ..., it is con-
                      sidered to be an assignment statement.  If the expres-
                      sion is not an assignment statement, the expression is
                      evaluated and printed to the output.  After the number
                      is printed, a newline is printed.  For example, ``a=1''
                      is an assignment statement and ``(a=1)'' is an expres-
                      sion that has an embedded assignment.  All numbers that
                      are printed are printed in the base specified by the
                      variable obase.  The legal values for obase are 2
                      through BC_BASE_MAX.  (See the section LIMITS.)  For
                      bases 2 through 16, the usual method of writing numbers
                      is used.  For bases greater than 16, bc uses a multi-
                      character digit method of printing the numbers where
                      each higher base digit is printed as a base 10 number.
                      The multi-character digits are separated by spaces.
                      Each digit contains the number of characters required to
                      represent the base ten value of ``obase-1''.  Since num-
                      bers are of arbitrary precision, some numbers may not be
                      printable on a single output line.  These long numbers
                      will be split across lines using the ``\'' as the last
                      character on a line.  The maximum number of characters
                      printed per line is 70.  Due to the interactive nature
                      of bc, printing a number causes the side effect of
                      assigning the printed value to the special variable
                      last.  This allows the user to recover the last value
                      printed without having to retype the expression that
                      printed the number.  Assigning to last is legal and will
                      overwrite the last printed value with the assigned
                      value.  The newly assigned value will remain until the
                      next number is printed or another value is assigned to
                      last.  (Some installations may allow the use of a single
                      period (.) which is not part of a number as a short hand
                      notation for last.)

     string           The string is printed to the output.  Strings start with
                      a double quote character and contain all characters
                      until the next double quote character.  All characters
                      are take literally, including any newline.  No newline
                      character is printed after the string.

     print list       The print statement (an extension) provides another
                      method of output.  The list is a list of strings and
                      expressions separated by commas.  Each string or expres-
                      sion is printed in the order of the list.  No terminat-
                      ing newline is printed.  Expressions are evaluated and
                      their value is printed and assigned to the variable
                      last.  Strings in the print statement are printed to the
                      output and may contain special characters.  Special
                      characters start with the backslash character (\).  The
                      special characters recognized by bc are `a' (alert or
                      bell), `b' (backspace), `f' (form feed), `n' (newline),
                      `r' (carriage return), `q' (double quote), `t' (tab),
                      and `\' (backslash).  Any other character following the
                      backslash will be ignored.

     { statement_list }
                      This is the compound statement.  It allows multiple
                      statements to be grouped together for execution.

     if (expression) statement1 [else statement2]
                      The if statement evaluates the expression and executes
                      statement1 or statement2 depending on the value of the
                      expression.  If the expression is non-zero, statement1
                      is executed.  If statement2 is present and the value of
                      the expression is 0, then statement2 is executed.  (The
                      else clause is an extension.)

     while (expression) statement
                      The while statement will execute the statement while the
                      expression is non-zero.  It evaluates the expression
                      before each execution of the statement.  Termination of
                      the loop is caused by a zero expression value or the
                      execution of a break statement.

     for ([expression1]; [expression2]; [expression3]) statement
                      The for statement controls repeated execution of the
                      statement.  Expression1 is evaluated before the loop.
                      Expression2 is evaluated before each execution of the
                      statement.  If it is non-zero, the statement is evalu-
                      ated.  If it is zero, the loop is terminated.  After
                      each execution of the statement, expression3 is evalu-
                      ated before the reevaluation of expression2.  If
                      expression1 or expression3 are missing, nothing is eval-
                      uated at the point they would be evaluated.  If
                      expression2 is missing, it is the same as substituting
                      the value 1 for expression2.  (The optional expressions
                      are an extension.  POSIX bc requires all three expres-
                      sions.)  The following is equivalent code for the for
                      statement:

                      expression1;
                      while (expression2) {
                         statement;
                         expression3;
                      }

     break            This statement causes a forced exit of the most recent
                      enclosing while statement or for statement.

     continue         The continue statement (an extension) causes the most
                      recent enclosing for statement to start the next itera-
                      tion.

     halt             The halt statement (an extension) is an executed state-
                      ment that causes the bc processor to quit only when it
                      is executed.  For example,
                            if (0 == 1) halt
                      will not cause bc to terminate because the halt is not
                      executed.

     return           Return the value 0 from a function.  (See the section on
                      functions.)

     return (expression)
                      Return the value of the expression from a function.
                      (See the section on  functions.)  As an extension, the
                      parenthesis are not required.

   PSEUDO STATEMENTS
     These statements are not statements in the traditional sense.  They are
     not executed statements.  Their function is performed at "compile" time.

     limits           Print the local limits enforced by the local version of
                      bc This is an extension.

     quit             When the quit statement is read, the bc processor is
                      terminated, regardless of where the quit statement is
                      found.  For example,
                            if (0 == 1) quit
                      will cause bc to terminate.

     warranty         Print a longer warranty notice.  This is an extension.

   FUNCTIONS
     Functions provide a method of defining a computation that can be executed
     later.  Functions in bc always compute a value and return it to the
     caller.  Function definitions are "dynamic" in the sense that a function
     is undefined until a definition is encountered in the input.  That defi-
     nition is then used until another definition function for the same name
     is encountered.  The new definition then replaces the older definition.
     A function is defined as follows:

     define name ( parameters ) { newline
         auto_list   statement_list }
     A function call is just an expression of the form ``name (parameters)''.

     Parameters are numbers or arrays (an extension).  In the function defini-
     tion, zero or more parameters are defined by listing their names sepa-
     rated by commas.  All parameters are call by value parameters.  Arrays
     are specified in the parameter definition by the notation ``name []''.
     In the function call, actual parameters are full expressions for number
     parameters.  The same notation is used for passing arrays as for defining
     array parameters.  The named array is passed by value to the function.
     Since function definitions are dynamic, parameter numbers and types are
     checked when a function is called.  Any mismatch in number or types of
     parameters will cause a runtime error.  A runtime error will also occur
     for the call to an undefined function.

     The auto_list is an optional list of variables that are for "local" use.
     The syntax of the auto list (if present) is ``auto name, ...;''.  (The
     semicolon is optional.)  Each name is the name of an auto variable.
     Arrays may be specified by using the same notation as used in parameters.
     These variables have their values pushed onto a stack at the start of the
     function.  The variables are then initialized to zero and used throughout
     the execution of the function.  At function exit, these variables are
     popped so that the original value (at the time of the function call) of
     these variables are restored.  The parameters are really auto variables
     that are initialized to a value provided in the function call.  Auto
     variables are different than traditional local variables because if func-
     tion A calls function B, B may access function A's auto variables by just
     using the same name, unless function B has called them auto variables.
     Due to the fact that auto variables and parameters are pushed onto a
     stack, bc supports recursive functions.

     The function body is a list of bc statements.  Again, statements are sep-
     arated by semicolons or newlines.  Return statements cause the termina-
     tion of a function and the return of a value.  There are two versions of
     the return statement.  The first form, ``return'', returns the value 0 to
     the calling expression.  The second form, ``return (expression)'', com-
     putes the value of the expression and returns that value to the calling
     expression.  There is an implied ``return (0)'' at the end of every func-
     tion.  This allows a function to terminate and return 0 without an
     explicit return statement.

     Functions also change the usage of the variable ibase.  All constants in
     the function body will be converted using the value of ibase at the time
     of the function call.  Changes of ibase will be ignored during the execu-
     tion of the function except for the standard function read, which will
     always use the current value of ibase for conversion of numbers.

     Several extensions have been added to functions.  First, the format of
     the definition has been slightly relaxed.  The standard requires the
     opening brace be on the same line as the define keyword and all other
     parts must be on following lines.  This version of bc will allow any num-
     ber of newlines before and after the opening brace of the function.  For
     example, the following definitions are legal.

     define d (n) { return (2*n); }
     define d (n)
       { return (2*n); }

     Functions may be defined as void.  A void funtion returns no value and
     thus may not be used in any place that needs a value.  A void function
     does not produce any output when called by itself on an input line.  The
     key word void is placed between the key word define and the function
     name.  For example, consider the following session.

     define py (y) { print "--->", y, "<---", "0; }
     define void px (x) { print "--->", x, "<---", "0; }
     py(1)
     --->1<---
     0
     px(1)
     --->1<---
     Since py is not a void function, the call of py (1) prints the desired
     output and then prints a second line that is the value of the function.
     Since the value of a function that is not given an explicit return state-
     ment is zero, the zero is printed.  For px (1), no zero is printed
     because the function is a void function.

     Also, call by variable for arrays was added.  To declare a call by vari-
     able array, the declaration of the array parameter in the function defi-
     nition looks like ``name []''.  The call to the function remains the same
     as call by value arrays.

   MATH LIBRARY
     If bc is invoked with the -l option, a math library is preloaded and the
     default scale is set to 20.  The math functions will calculate their
     results to the scale set at the time of their call.  The math library
     defines the following functions:

     s (x)            The sine of x, x is in radians.

     c (x)            The cosine of x, x is in radians.

     a (x)            The arctangent of x, arctangent returns radians.

     l (x)            The natural logarithm of x.

     e (x)            The exponential function of raising e to the value x.

     j (n, x)         The Bessel function of integer order n of x.

ENVIRONMENT
     The following environment variables are processed by bc:

     POSIXLY_CORRECT  This is the same as the -s option.

     BC_ENV_ARGS      This is another mechanism to get arguments to bc.  The
                      format is the same as the command line arguments.  These
                      arguments are processed first, so any files listed in
                      the environment arguments are processed before any com-
                      mand line argument files.  This allows the user to set
                      up "standard" options and files to be processed at every
                      invocation of bc.  The files in the environment vari-
                      ables would typically contain function definitions for
                      functions the user wants defined every time bc is run.

     BC_LINE_LENGTH   This should be an integer specifying the number of char-
                      acters in an output line for numbers.  This includes the
                      backslash and newline characters for long numbers.

EXAMPLES
     In /bin/sh, the following will assign the value of pi to the shell vari-
     able pi.

     pi=$(echo "scale=10; 4*a(1)" | bc -l)

     The following is the definition of the exponential function used in the
     math library.  This function is written in POSIX bc.

     scale = 20

     /* Uses the fact that e^x = (e^(x/2))^2
        When x is small enough, we use the series:
          e^x = 1 + x + x^2/2! + x^3/3! + ...
     */

     define e(x) {
       auto  a, d, e, f, i, m, v, z

       /* Check the sign of x. */
       if (x<0) {
         m = 1
         x = -x
       }

       /* Precondition x. */
       z = scale;
       scale = 4 + z + .44*x;
       while (x > 1) {
         f += 1;
         x /= 2;
       }

       /* Initialize the variables. */
       v = 1+x
       a = x
       d = 1

       for (i=2; 1; i++) {
         e = (a *= x) / (d *= i)
         if (e == 0) {
           if (f>0) while (f--)  v = v*v;
           scale = z
           if (m) return (1/v);
           return (v/1);
         }
         v += e
       }
     }

     The following is code that uses the extended features of bc to implement
     a simple program for calculating checkbook balances.  This program is
     best kept in a file so that it can be used many times without having to
     retype it at every use.

     scale=2
     print "\nCheck book program!\n"
     print "  Remember, deposits are negative transactions.\n"
     print "  Exit by a 0 transaction.\n\n"

     print "Initial balance? "; bal = read()
     bal /= 1
     print "\n"
     while (1) {
       "current balance = "; bal
       "transaction? "; trans = read()
       if (trans == 0) break;
       bal -= trans
       bal /= 1
     }
     quit

     The following is the definition of the recursive factorial function.

     define f (x) {
       if (x <= 1) return (1);
       return (f(x-1) * x);
     }

   EDITLINE OPTIONS
     bc is compiled using the editline(3) library.  This allows the user to do
     editing of lines before sending them to bc.  It also allows for a history
     of previous lines typed.  This adds to bc one more special variable.
     This special variable, history is the number of lines of history
     retained.  The default value of -1 means that an unlimited number of his-
     tory lines are retained.  Setting the value of history to a positive num-
     ber restricts the number of history lines to the number given.  The value
     of 0 disables the history feature.  For more information, read the user
     manual for the editline(3) library.

   DIFFERENCES
     This version of bc was implemented from the POSIX P1003.2/D11 draft and
     contains several differences and extensions relative to the draft and
     traditional implementations.  It is not implemented in the traditional
     way using dc(1).  This version is a single process which parses and runs
     a byte code translation of the program.  There is an "undocumented"
     option (-c) that causes the program to output the byte code to the stan-
     dard output instead of running it.  It was mainly used for debugging the
     parser and preparing the math library.

     A major source of differences is extensions, where a feature is extended
     to add more functionality and additions, where new features are added.
     The following is the list of differences and extensions.

     LANG environment
                      This version does not conform to the POSIX standard in
                      the processing of the LANG environment variable and all
                      environment variables starting with LC_.

     names            Traditional and POSIX bc have single letter names for
                      functions, variables and arrays.  They have been
                      extended to be multi-character names that start with a
                      letter and may contain letters, numbers and the under-
                      score character.

     strings          Strings are not allowed to contain NUL characters.
                      POSIX says all characters must be included in strings.
                      last POSIX bc does not have a last variable.  Some
                      implementations of bc use the period (.) in a similar
                      way.

     comparisons      POSIX bc allows comparisons only in the if statement,
                      the while statement, and the second expression of the
                      for statement.  Also, only one relational operation is
                      allowed in each of those statements.

     if statement, else clause
                      POSIX bc does not have an else clause.

     for statement    POSIX bc requires all expressions to be present in the
                      for statement.

     &&, ||, !        POSIX bc does not have the logical operators.

     read function    POSIX bc does not have a read function.

     print statement  POSIX bc does not have a print statement .

     continue statement
                      POSIX bc does not have a continue statement.

     return statement
                      POSIX bc requires parentheses around the return expres-
                      sion.

     array parameters
                      POSIX bc does not (currently) support array parameters
                      in full.  The POSIX grammar allows for arrays in func-
                      tion definitions, but does not provide a method to spec-
                      ify an array as an actual parameter.  (This is most
                      likely an oversight in the grammar.)  Traditional imple-
                      mentations of bc have only call-by-value array parame-
                      ters.

     function format  POSIX bc requires the opening brace on the same line as
                      the define key word and the auto statement on the next
                      line.

     =+, =-, =*, =/, =%, =^
                      POSIX bc does not require these "old style" assignment
                      operators to be defined.  This version may allow these
                      "old style" assignments.  Use the limits statement to
                      see if the installed version supports them.  If it does
                      support the "old style" assignment operators, the state-
                      ment ``a =- 1'' will decrement a by 1 instead of setting
                      a to the value -1.

     spaces in numbers
                      Other implementations of bc allow spaces in numbers.
                      For example, ``x=1 3'' would assign the value 13 to the
                      variable x.  The same statement would cause a syntax
                      error in this version of bc.

     errors and execution
                      This implementation varies from other implementations in
                      terms of what code will be executed when syntax and
                      other errors are found in the program.  If a syntax
                      error is found in a function definition, error recovery
                      tries to find the beginning of a statement and continue
                      to parse the function.  Once a syntax error is found in
                      the function, the function will not be callable and
                      becomes undefined.  Syntax errors in the interactive
                      execution code will invalidate the current execution
                      block.  The execution block is terminated by an end of
                      line that appears after a complete sequence of state-
                      ments.  For example,

                      a = 1
                      b = 2
                      has two execution blocks and

                      { a = 1
                        b = 2 }
                      has one execution block.  Any runtime error will termi-
                      nate the execution of the current execution block.  A
                      runtime warning will not terminate the current execution
                      block.

     interrupts       During an interactive session, the SIGINT signal (usu-
                      ally generated by the control-C character from the ter-
                      minal) will cause execution of the current execution
                      block to be interrupted.  It will display a "runtime"
                      error indicating which function was interrupted.  After
                      all runtime structures have been cleaned up, a message
                      will be printed to notify the user that bc is ready for
                      more input.  All previously defined functions remain
                      defined and the value of all non-auto variables are the
                      value at the point of interruption.  All auto variables
                      and function parameters are removed during the clean up
                      process.  During a non-interactive session, the SIGINT
                      signal will terminate the entire run of bc.

   LIMITS
     The following are the limits currently in place for this bc processor.
     Some of them may have been changed by an installation.  Use the limits
     statement to see the actual values.

     BC_BASE_MAX      The maximum output base is currently set at 999.  The
                      maximum input base is 16.

     BC_DIM_MAX       This is currently an arbitrary limit of 65535 as dis-
                      tributed.  Your installation may be different.

     BC_SCALE_MAX     The number of digits after the decimal point is limited
                      to INT_MAX digits.  Also, the number of digits before
                      the decimal point is limited to INT_MAX digits.

     BC_STRING_MAX    The limit on the number of characters in a string is
                      INT_MAX characters.

     exponent         The value of the exponent in the raise operation (^) is
                      limited to LONG_MAX.

     variable names   The current limit on the number of unique names is 32767
                      for each of simple variables, arrays and functions.

DIAGNOSTICS
     If any file on the command line can not be opened, bc will report that
     the file is unavailable and terminate.  Also, there are compile and run
     time diagnostics that should be self-explanatory.

HISTORY
     This man page documents bc version nb1.0.

AUTHORS
     Philip A. Nelson <phil@NetBSD.org>

   ACKNOWLEDGEMENTS
     The author would like to thank Steve Sommars for his extensive help in
     testing the implementation.  Many great suggestions were given.  This is
     a much better product due to his involvement.

BUGS
     Error recovery is not very good yet.

NetBSD 8.0                      April 16, 2017                      NetBSD 8.0

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