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DC(1) DC(1)NAMEdc - an arbitrary precision calculatorSYNOPSISdc [-V] [--version] [-h] [--help] [-e scriptexpression] [--expression=scriptexpression] [-f scriptfile] [--file=scriptfile] [file(1,n) ...]DESCRIPTIONDc 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(3,n) 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(8,n) 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(1,8) 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(1,8) succession, separate them with spaces or newlines. These have no meaning as commands.OPTIONSDc may be invoked with the following command-line options:-V--versionPrint out the version(1,3,5) of dc that is being run and a copyright notice, then exit.-h--helpPrint a usage message briefly summarizing these command-line options and the bug-reporting address, then exit.-escript--expression=script Add the commands in(1,8) script to the set(7,n,1 builtins) of commands to be run while processing the input.-fscript-file--file=script-file Add the commands contained in(1,8) the file(1,n) script-file to the set(7,n,1 builtins) 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(1,n) name of-refers to the standard input stream. The standard input will processed if(3,n) no file(1,n) names are specified.Printing CommandspPrints the value on the top of the stack, without altering the stack. A newline is printed after the value.nPrints the value on the top of the stack, popping it off, and does not print a newline after.PPops off the value on top of the stack. If it it a string(3,n), 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 sequenceKSK 0k1/ [_1*]sx d0>x [256~aPd0<x]dsxxsxLKkcould also accomplish this function, except for the side- effect of clobbering the x register.fPrints the entire contents of the stack without altering any- thing. This is a good command to use if(3,n) 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(1,8) the result depends on the current precision value and the number of fraction digits in(1,8) 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 sequenceSd 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(1,8) the division is specified by the precision value. (The sequenceSdSn lnld/LnLd%could also accomplish this function, with slightly differ- ent error(8,n) 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(1,8) 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(3,n) exponen- tiated, which should be an integer. For small integers this is like the sequenceSm^Lm%, but, unlike^, this command will work with arbitrarily large exponents.vPops one value, computes its square root, and pushes that. The precision value specifies the number of fraction digits in(1,8) the result. Most arithmetic operations are affected by the ``precision value'', which you can set(7,n,1 builtins) with thekcommand. The default precision value is zero, which means that all arithmetic except for addition and subtrac- tion produces integer results.Stack ControlcClears the stack, rendering it empty.dDuplicates the value on the top of the stack, pushing another copy of it. Thus, ``4d*p'' computes 4 squared and prints it.rReverses the order of (swaps) the top two values on the stack.RegistersDc provides at least 256 memory registers, each named(5,8) by a single char- acter. You can store a number or a string(3,n) in(1,8) 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(1,8) 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(1,8) register r's stack, if(3,n) any, is now accessible via thelr command.ParametersDc 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(1,8) the result of most arithmetic operations. The input radix controls the interpretation of numbers typed in(1,8); all numbers typed in(1,8) 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(1,8) decimal digits, regardless of the current input or output radix.iPops the value off the top of the stack and uses it to set(7,n,1 builtins) the input radix.oPops the value off the top of the stack and uses it to set(7,n,1 builtins) the output radix.kPops the value off the top of the stack and uses it to set(7,n,1 builtins) the precision.IPushes the current input radix on the stack.OPushes the current output radix on the stack.KPushes the current precision on the stack.StringsDc 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(3,n) are processed as dc commands). All registers and the stack can hold strings, and dc always knows whether any given object is a string(3,n) or a number. Some commands such as arithmetic operations demand numbers as arguments and print errors if(3,n) given strings. Other commands can accept(2,8) either a number or a string(3,n); for example, thepcommand can accept(2,8) either and prints the object according to its type.[characters]Makes a string(3,n) containing characters (contained between balanced[and]characters), and pushes it on the stack. For example,[foo]Pprints the charactersfoo(with no newline).aThe top-of-stack is popped. If it was a number, then the low- order byte of this number is converted into a string(3,n) and pushed onto the stack. Otherwise the top-of-stack was a string(3,n), and the first character of that string(3,n) is pushed back.xPops a value off the stack and executes it as a macro. Normally it should be a string(3,n); if(3,n) it is a number, it is simply pushed back onto the stack. For example,[1p]xexecutes the macro1pwhich pushes1on the stack and prints1on a separate line. Macros are most often stored in(1,8) registers;[1p]sastores a macro to print1into registera, andlaxinvokes 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(3,n) the original top-of-stack is greater. Thus,1 2>awill invoke registera's contents and2 1>awill not.!>r Similar but invokes the macro if(3,n) the original top-of-stack is not greater than (less(1,3) than or equal to) what was the second-to- top.<r Similar but invokes the macro if(3,n) the original top-of-stack is less.!<r Similar but invokes the macro if(3,n) the original top-of-stack is not less(1,3) than (greater than or equal to) what was the second-to- top.=r Similar but invokes the macro if(3,n) the two numbers popped are equal.!=r Similar but invokes the macro if(3,n) 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.qexits 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, theqcommand will cause dc to exit.QPops a value off the stack and uses it as a count of levels of macro execution to be exited. Thus,3Qexits three levels. TheQcommand will never cause dc to exit.Status InquiryZPops a value off the stack, calculates the number of digits it has (or number of characters, if(3,n) it is a string(3,n)) and pushes that number.XPops a value off the stack, calculates the number of fraction digits it has, and pushes that number. For a string(3,n), the value pushed is 0.zPushes the current stack depth: the number of objects on the stack before the execution of thezcommand.Miscellaneous!Will run the rest of the line as a system command. Note that parsing of the !<, !=, and !> commands take precedence, so if(3,n) 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(1,8) 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. Thus1 0:a 0Sa 2 0:a La 0;apwill print 1, because the 2 was stored in(1,8) an instance of 0:a that was later popped.BUGSEmail bug reports tobug-dc@gnu.org. GNU Project 1997-03-25 DC(1)