wrapdc/README.md

# NAME

**wrapdc** - Command line wrapper for `dc (1)`

# SYNTAX

**wrapdc** [-v] [pseudocommand] [command]

# DESCRIPTION

This wrapper renders `dc` more usable as a command line calculator by:

- defining commonly used macros for more complex operations
- saving precision, top of stack, and registers 0 to 9 ("memories")
  from one invocation to the next in the status file `$HOME/.wdcrc`
- saving last top of stack value in `/tmp/wdc-$USER` for further direct use
  (change file name in the source, if desired)

# PREREQUISITES

The POSIX conform program `dc` ("desktop calculator") and standard shell `sh`
must be installed and accessible through `$PATH`.

# USAGE

The wrapper script `wrapdc.sh` can be called directly (if executable) or by
invoking `sh wrapdc.sh` with optional arguments.

If arguments are given, they are interpreted as one line of commands,
which is executed, and then the script finishes.

If no arguments are given, the script enters a loop: read a line
of input from STDIN, execute it, and display the resulting top-of-stack,
together with the top of stack in exponential notation
(which currently only works as usual for absolute values greater than 1).
The loop (and script) finishes, when `quit` or CTRL-D is entered.

All normal `dc` commands can be used, see the corresponding manual.
In particular, negative numbers must be entered with a leading `_`
(underscore) as minus sign, not a `-` (dash), because the latter is
indicating the command 'subtraction'.

As an extension, values can also be entered in exponential notation,
e.g `12e3` is converted to `1200` and `1E_2` to `.01` (if precision is 2).

The `dc` command `r` (exchanging the two topmost stack entries) is emulated
with some internal register operations, as it is a GNU extension and may not
always be available. This may render complex operations somewhat slower.

There is also a macro `drop` for removing the topmost stack value.

In addition to the `quit` command, the following pseudocommands are handled
directly by the wrapper:

- `help` shows some initial hints and this pseudocommand list
- `list` displays a list of predefined macros; please note the syntax is
  according to `sed` i.e certain characters are escaped with backslash
- `verb` activates verbose mode, which displays before each execution of
  input line the input from the status file as well as the input line with
  expanded macro definitions
- `noverb` deactivates verbose mode
- `clear` resets precision and all memories and stack registers

All pseudocommands must be entered at the beginning of a line, and all
subsequent input on this line will be ignored.

Verbose mode can also be activated with the command line option `-v` which
may be useful in case of direct input with further command line arguments.

## Statistical Calculations

The registers ("memories") 1 to 6 have special meanings for statistical
calculations with `$...` macros, and are used as follows:

- reg.1 = number of entries `n`
- reg.2 = sum of X values `sumX`
- reg.3 = sum of X^2 values `sumX2`
- reg.4 = sum of Y values `sumY`
- reg.5 = sum of Y^2 values `sumY2`
- reg.6 = sum of XY values `sumXY`

The command `$` or `$+` adds the two topmost stack values to the statistical
registers as follows: the topmost value is added to reg.2 and its square
value to reg.3, the second to topmost value in the same way to reg.4 and 5,
and the product of the two values to reg.6. reg.1 is then increased by 1.

The command `$-` subtracts the values in the inverse way. Please note: due to
rounding errors, `$-` is not the inverse of `$+` in some cases.

The command `$m` calculates the mean values reg.2/reg.1 and reg.4/reg.1.

_(More commands will be added in future versions.)_

# EXAMPLES

(We assume `wrapdc.sh` is executable in `$PATH` .)

	$ wrapdc.sh 5k 2v # precision 5, 2 on stack, calculate square root
	1.41421 # 1.41421E0
	$ wrapdc.sh 3 7/ # 3, divide by 7 (precision was saved from last run)
	.42857 # 4.28570E-1
	$ wrapdc.sh list # display macros (and top of stack before finishing)
	: %t # percent part: X:=100*X/Y, Y kept
	: %d # percent delta: X:=100*(X-Y)/Y, Y kept
	: % # percentage: X:=X*Y/100, Y kept
	: rem # remainder: X:=Y%X (instead of normal % command)
	: sto\(.\) # sto.: store with copying (i.e keep value on stack)
	: fact # factorial: X:=X!
	: neg # negate: X:=-X
	: \$m # mean value: X:=reg.2/reg.1, Y:=reg.4/reg.1
	: \$- # remove statistic entry
	: \$+* # add statistic entry
	: [eE]\(_*[0-9][0-9]*\) # infix exponential: X:=X*10^N
	: drop # stack drop
	: r # revert: X:=Y, Y:=X (r is a GNU extension)
	.42857 # 4.28570E-1
	$ wrapdc.sh 42fact sto1 # calculate 42! (factorial) and store in '1'
	1405006117752879898543142606244511569936384000000000 # 1.40500E51
	$ wrapdc.sh 2k234 7%+ # precision 2, add 7% to 234
	250.38 # 2.50E2
	$ wrapdc.sh 234r%t # which is how many % of 234?
	107.00 # 1.07E2
	$ wrapdc.sh l1 40fact/ # divide memory '1' by the factorial of 40
	1722.00 # 1.72E3
	$ wrapdc.sh 41 42* # which of course is 42!/40!=41*42
	1722 # 1.72E3
	$ wrapdc.sh clear # set all registers to 0 (prepare for statistics)
	0 # 0E-1
	$ wrapdc.sh '1$2$3$4$l2' # entries: 1,2,3,4; load reg.2 (sum)
	10 # 1.00E1
	$ wrapdc.sh '$m' # display average of statistic entries
	2.50 # 2.50E0
	$ wrapdc.sh 1234fact|sed -e 's/.*#//' # 1234!, only display exponential
	 5.10E3280
	$ wrapdc.sh 1233fact/ # just checking: 1234!/1233!=1234
	1234.00 # 1.23E3
	$ wrapdc.sh 1.23e3- # just checking exponential notation
	4.00 # 4.00E0

Note: the example with `41 42*` only works if there is no file
beginning with '42' in the current directory, otherwise the shell
will expand its name before passing on the argument to the wrapper
script. In this case, you should escape the `*` or put the arguments
in apostrophes `'41 42*'` or simply start the wrapper without
arguments, and do the calculations in its internal command loop.
Preventing shell expansion is also necessary in the statistics example.

# MACROS

Macros can be easily added to the script, if you know `sed` syntax.
They are defined in the shell variable `mcrs.` where each one should be
written on a separate line with comma `,` as pattern delimiters, followed
by `;#` and a comment explaining its use.
This allows the `list` pseudocommand to display them together with the
comment. _Do not prepend any white space to the definition, otherwise
it will not be displayed by `list`!_

Please note that the macro expansion is global and "stupid" -- you should
therefore define the longer commands first, and single character commands
only at the very end. Otherwise, e.g the `rem` command would first have its
`r` expanded as the "revert" command, therefore `rem` expansion would fail.

# FILES

- The status between invocations is stored in the file `$HOME/.wdcrc` as a list of `dc` commands.
- The last top of stack value is stored in `/tmp/wdc-$USER`.

_These file names can be easily changed at the beginning of the script._

# BUGS

_(certainly, but none known at this moment)_

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# AUTHOR

Yargo Bonetti