Provided by: dc_1.06.95-2_amd64 bug

NAME

       dc - an arbitrary precision calculator

SYNOPSIS

       dc [-V] [--version] [-h] [--help]
          [-e scriptexpression] [--expression=scriptexpression]
          [-f scriptfile] [--file=scriptfile]
          [file ...]

DESCRIPTION

       dc  is a reverse-polish desk calculator which supports unlimited precision arithmetic.  It
       also allows you to define and call macros.  Normally dc reads from the standard input;  if
       any  command  arguments are given to it, they are filenames, and dc reads and executes the
       contents of the files before reading  from  standard  input.   All  normal  output  is  to
       standard output; all error output is to standard error.

       A reverse-polish calculator stores numbers on a stack.  Entering a number pushes it on the
       stack.  Arithmetic operations pop arguments off the stack and push the results.

       To enter a number in dc, type the digits (using upper case letters A through F as "digits"
       when  working  with  input  bases  greater  than  ten),  with  an  optional decimal point.
       Exponential notation is not supported.  To enter a negative number, begin the number  with
       ``_''.  ``-'' cannot be used for this, as it is a binary operator for subtraction instead.
       To enter two numbers in succession, separate them with spaces or newlines.  These have  no
       meaning as commands.

OPTIONS

       dc may be invoked with the following command-line options:

       -V

       --version
              Print out the version of dc that is being run and a copyright notice, then exit.

       -h

       --help Print  a  usage message briefly summarizing these command-line options and the bug-
              reporting address, then exit.

       -e script

       --expression=script
              Add the commands in script to the set of commands to be run  while  processing  the
              input.

       -f script-file

       --file=script-file
              Add the commands contained in the file script-file to the set of commands to be run
              while processing the input.

       If any command-line parameters remain after processing the  above,  these  parameters  are
       interpreted  as  the names of input files to be processed.  A file name of - refers to the
       standard input  stream.   The  standard  input  will  processed  if  no  script  files  or
       expressions are specified.

Printing Commands

       p      Prints the value on the top of the stack, without altering the stack.  A newline is
              printed after the value.

       n      Prints the value on the top of the stack, popping it off,  and  does  not  print  a
              newline after.

       P      Pops  off  the  value on top of the stack.  If it it a string, it is simply printed
              without a trailing newline.  Otherwise it is a number, and the integer  portion  of
              its  absolute value is printed out as a "base (UCHAR_MAX+1)" byte stream.  Assuming
              that (UCHAR_MAX+1) is 256 (as it  is  on  most  machines  with  8-bit  bytes),  the
              sequence      KSK0k1/_1Ss      [ls*]Sxd0>x     [256~Ssd0<x]dsxxsx[q]Sq[Lsd0>qaPlxx]
              dsxxsx0sqLqsxLxLK+k could also accomplish this function.  (Much of  the  complexity
              of the above native-dc code is due to the ~ computing the characters backwards, and
              the desire to ensure that all registers wind up back in their original states.)

       f      Prints the entire contents of the stack without altering anything.  This is a  good
              command  to  use  if  you  are  lost  or want to figure out what the effect of some
              command has been.

Arithmetic

       +      Pops two values off the stack, adds them, and pushes the result.  The precision  of
              the  result  is determined only by the values of the arguments, and is enough to be
              exact.

       -      Pops two values, subtracts the first one popped from the  second  one  popped,  and
              pushes the result.

       *      Pops  two  values,  multiplies them, and pushes the result.  The number of fraction
              digits in the result depends on the current  precision  value  and  the  number  of
              fraction digits in the two arguments.

       /      Pops  two  values,  divides  the  second  one popped from the first one popped, and
              pushes the result.  The number of fraction digits is  specified  by  the  precision
              value.

       %      Pops  two  values,  computes the remainder of the division that the / command would
              do, and pushes that.  The value computed is  the  same  as  that  computed  by  the
              sequence Sd dld/ Ld*- .

       ~      Pops  two  values,  divides  the  second one popped from the first one popped.  The
              quotient is pushed first, and the remainder is pushed next.  The number of fraction
              digits  used  in  the  division is specified by the precision value.  (The sequence
              SdSn lnld/ LnLd% could also accomplish this function, with slightly different error
              checking.)

       ^      Pops two values and exponentiates, using the first value popped as the exponent and
              the second popped as the base.  The fraction part of the exponent is ignored.   The
              precision value specifies the number of fraction digits in the result.

       |      Pops three values and computes a modular exponentiation.  The first value popped is
              used as the reduction modulus; this value must be a non-zero number, and should  be
              an  integer.   The second popped is used as the exponent; this value must be a non-
              negative number, and any fractional part of this exponent  will  be  ignored.   The
              third  value  popped  is  the  base  which  gets  exponentiated, which should be an
              integer.  For small integers this is like the sequence Sm^Lm%, but, unlike ^,  this
              command will work with arbitrarily large exponents.

       v      Pops  one  value,  computes  its square root, and pushes that.  The precision value
              specifies the number of fraction digits in the result.

       Most arithmetic operations are affected by the ``precision value'', which you can set with
       the  k  command.   The  default  precision  value is zero, which means that all arithmetic
       except for addition and subtraction produces integer results.

Stack Control

       c      Clears the stack, rendering it empty.

       d      Duplicates the value on the top of the stack, pushing another copy  of  it.   Thus,
              ``4d*p'' computes 4 squared and prints it.

       r      Reverses  the  order of (swaps) the top two values on the stack.  (This can also be
              accomplished with the sequence SaSbLaLb.)

Registers

       dc provides at least 256 memory registers, each named by  a  single  character.   You  can
       store a number or a string in a register and retrieve it later.

       sr     Pop the value off the top of the stack and store it into register r.

       lr     Copy  the  value in register r and push it onto the stack.  This does not alter the
              contents of r.

       Each register also contains its own stack.  The current register value is the top  of  the
       register's stack.

       Sr     Pop  the  value  off  the  top  of  the  (main) stack and push it onto the stack of
              register r.  The previous value of the register becomes inaccessible.

       Lr     Pop the value off the top of register r's stack and push it onto  the  main  stack.
              The  previous  value  in  register  r's stack, if any, is now accessible via the lr
              command.

Parameters

       dc has three parameters that control its operation: the precision, the  input  radix,  and
       the  output  radix.   The precision specifies the number of fraction digits to keep in the
       result of most arithmetic operations.  The input  radix  controls  the  interpretation  of
       numbers  typed  in;  all  numbers  typed  in use this radix.  The output radix is used for
       printing numbers.

       The input and output radices are separate parameters; you can make them unequal, which can
       be  useful  or confusing.  The input radix must be between 2 and 16 inclusive.  The output
       radix must be at least 2.  The precision must be zero or greater.  The precision is always
       measured in decimal digits, regardless of the current input or output radix.

       i      Pops the value off the top of the stack and uses it to set the input radix.

       o      Pops the value off the top of the stack and uses it to set the output radix.

       k      Pops the value off the top of the stack and uses it to set the precision.

       I      Pushes the current input radix on the stack.

       O      Pushes the current output radix on the stack.

       K      Pushes the current precision on the stack.

Strings

       dc  has a limited ability to operate on strings as well as on numbers; the only things you
       can do with strings are print them and execute  them  as  macros  (which  means  that  the
       contents  of  the  string  are processed as dc commands).  All registers and the stack can
       hold strings, and dc always knows whether any given object is a string or a number.   Some
       commands  such  as  arithmetic  operations demand numbers as arguments and print errors if
       given strings.  Other commands can accept either a number or a string; for example, the  p
       command can accept either and prints the object according to its type.

       [characters]
              Makes   a  string  containing  characters  (contained  between  balanced  [  and  ]
              characters), and pushes it on the stack.  For example, [foo]P prints the characters
              foo (with no newline).

       a      The  top-of-stack  is  popped.  If it was a number, then the low-order byte of this
              number is converted into a string and pushed onto the stack.  Otherwise the top-of-
              stack was a string, and the first character of that string is pushed back.

       x      Pops  a  value  off  the stack and executes it as a macro.  Normally it should be a
              string; if it is a number, it is simply pushed back onto the stack.   For  example,
              [1p]x  executes the macro 1p which pushes 1 on the stack and prints 1 on a separate
              line.

       Macros are most often stored in registers; [1p]sa stores a macro to print 1 into  register
       a, and lax invokes this macro.

       >r     Pops  two  values  off  the  stack  and  compares  them  assuming they are numbers,
              executing the contents of register r as a macro if  the  original  top-of-stack  is
              greater.  Thus, 1 2>a will invoke register a's contents and 2 1>a will not.

       !>r    Similar  but  invokes  the  macro  if the original top-of-stack is not greater than
              (less than or equal to) what was the second-to-top.

       <r     Similar but invokes the macro if the original top-of-stack is less.

       !<r    Similar but invokes the macro  if  the  original  top-of-stack  is  not  less  than
              (greater than or equal to) what was the second-to-top.

       =r     Similar but invokes the macro if the two numbers popped are equal.

       !=r    Similar but invokes the macro if the two numbers popped are not equal.

       ?      Reads  a  line  from  the terminal and executes it.  This command allows a macro to
              request input from the user.

       q      exits from a macro and also from the macro which invoked it.  If  called  from  the
              top  level,  or  from  a  macro which was called directly from the top level, the q
              command will cause dc to exit.

       Q      Pops a value off the stack and uses it as a count of levels of macro  execution  to
              be  exited.   Thus,  3Q  exits  three levels.  The Q command will never cause dc to
              exit.

Status Inquiry

       Z      Pops a value off the stack, calculates the number of digits it has  (or  number  of
              characters,  if  it  is  a  string)  and pushes that number.  The digit count for a
              number does not include any leading zeros, even if those appear to the right of the
              radix point.

       X      Pops  a  value  off the stack, calculates the number of fraction digits it has, and
              pushes that number.  For a string, the value pushed is 0.

       z      Pushes the current stack depth: the number of  objects  on  the  stack  before  the
              execution of the z command.

Miscellaneous

       !      Will  run  the  rest of the line as a system command.  Note that parsing of the !<,
              !=, and !> commands take precedence, so if you want to run a command starting  with
              <, =, or > you will need to add a space after the !.

       #      Will interpret the rest of the line as a comment.

       :r     Will  pop the top two values off of the stack.  The old second-to-top value will be
              stored in the array r, indexed by the old top-of-stack value.

       ;r     Pops the top-of-stack and uses it as an index into the array r.  The selected value
              is then pushed onto the stack.

       Note  that each stacked instance of a register has its own array associated with it.  Thus
       1 0:a 0Sa 2 0:a La 0;ap will print 1, because the 2 was stored in an instance of 0:a  that
       was later popped.

FILES

       ~/.dcrc        The commands in this file will be executed when dc is first run.

BUGS

       Email bug reports to bug-dc@gnu.org.