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dc - an arbitrary precision calculator

 

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 preci‐
        sion arithmetic.  It also allows you to define and call  macros.   Nor‐
        mally  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 num‐
        ber  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  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 file names are specified.
        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  KSK  0k1/  [_1*]sx d0>x [256~aPd0<x]dsxx
               sxLKk could also accomplish this function, except for the  side-
               effect of clobbering the x register.
 
        f      Prints  the  entire  contents of the stack without altering any‐
               thing.  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  dig‐
               its 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 differ‐
               ent 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-nega‐
               tive  number,  and  any fractional part of this exponent will be
               ignored.  The third value popped is the base which gets exponen‐
               tiated,  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 subtrac‐
        tion produces integer results.
        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.
 

Registers

        Dc provides at least 256 memory registers, each named by a single char‐
        acter.  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 regis‐
               ter 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 can 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.
        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.
 
        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 associ‐
        ated 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.
 

BUGS

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

Sections

Based on BSD UNIX
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