fish-shell/doc_src/cmds/math.rst

.. _cmd-math:

math - perform mathematics calculations
=======================================

Synopsis
--------

::

    math [-sN | --scale=N] [--] EXPRESSION


Description
-----------

``math`` is used to perform mathematical calculations. It supports all the usual operations such as addition, subtraction, etc. As well as functions like ``abs()``, ``sqrt()`` and ``log2()``.

By default, the output is as a float with trailing zeroes trimmed. To get a fixed representation, the ``--scale`` option can be used, including ``--scale=0`` for integer output.

Keep in mind that parameter expansion happens before expressions are evaluated. This can be very useful in order to perform calculations involving shell variables or the output of command substitutions, but it also means that parenthesis (``()``) and the asterisk (``*``) glob character have to be escaped or quoted. ``x`` can also be used to denote multiplication, but it needs to be followed by whitespace to distinguish it from hexadecimal numbers.

``math`` ignores whitespace between arguments and takes its input as multiple arguments (internally joined with a space), so ``math 2 +2`` and ``math "2 +    2"`` work the same. ``math 2 2`` is an error.

The following options are available:

- ``-sN`` or ``--scale=N`` sets the scale of the result. ``N`` must be an integer or the word "max" for the maximum scale. A scale of zero causes results to be rounded down to the nearest integer. So ``3/2`` returns ``1`` rather than ``2`` which ``1.5`` would normally round to. This is for compatibility with ``bc`` which was the basis for this command prior to fish 3.0.0. Scale values greater than zero causes the result to be rounded using the usual rules to the specified number of decimal places.

Return Values
-------------

If the expression is successfully evaluated and doesn't over/underflow or return NaN the return ``status`` is zero (success) else one.

Syntax
------

``math`` knows some operators, constants, functions and can (obviously) read numbers.

For numbers, ``.`` is always the radix character regardless of locale - ``2.5``, not ``2,5``. Scientific notation (``10e5``) is also available.

Operators
---------

``math`` knows the following operators:

- ``+`` for addition and ``-`` for subtraction.

- ``*`` or ``x`` for multiplication, ``/`` for division. (Note that ``*`` is the glob character and needs to be quoted or escaped, ``x`` needs to be followed by whitespace or it looks like ``0x`` hexadecimal notation.)

- ``^`` for exponentiation.

- ``%`` for modulo.

- ``(`` and ``)`` for grouping. (These need to be quoted or escaped because ``()`` denotes a command substitution.)

They are all used in an infix manner - ``5 + 2``, not ``+ 5 2``.

Constants
---------

``math`` knows the following constants:

- ``e`` - Euler's number.
- ``pi`` - You know that one. Half of Tau. (Tau is not implemented)

Use them without a leading ``$`` - ``pi - 3`` should be about 0.

Functions
---------

``math`` supports the following functions:

- ``abs``
- ``acos``
- ``asin``
- ``atan``
- ``atan2``
- ``bitand``, ``bitor`` and ``bitxor`` to perform bitwise operations. These will throw away any non-integer parts and interpret the rest as an int.
- ``ceil``
- ``cos``
- ``cosh``
- ``exp`` - the base-e exponential function
- ``fac`` - factorial
- ``floor``
- ``ln``
- ``log`` or ``log10`` - the base-10 logarithm
- ``ncr``
- ``npr``
- ``pow(x,y)`` returns x to the y (and can be written as ``x ^ y``)
- ``round`` - rounds to the nearest integer, away from 0
- ``sin``
- ``sinh``
- ``sqrt``
- ``tan``
- ``tanh``

All of the trigonometric functions use radians.

Examples
--------

``math 1+1`` outputs 2.

``math $status - 128`` outputs the numerical exit status of the last command minus 128.

``math 10 / 6`` outputs ``1.666667``.

``math -s0 10.0 / 6.0`` outputs ``1``.

``math -s3 10 / 6`` outputs ``1.666``.

``math "sin(pi)"`` outputs ``0``.

``math 5 \* 2`` or ``math "5 * 2"`` or ``math 5 "*" 2`` all output ``10``.

``math 0xFF`` outputs 255, ``math 0 x 3`` outputs 0 (because it computes 0 multiplied by 3).

``math "bitand(0xFE, 0x2e)"`` outputs 46.

``math "bitor(9,2)"`` outputs 11.

Compatibility notes
-------------------

Fish 1.x and 2.x releases relied on the ``bc`` command for handling ``math`` expressions. Starting with fish 3.0.0 fish uses the tinyexpr library and evaluates the expression without the involvement of any external commands.

You don't need to use ``--`` before the expression even if it begins with a minus sign which might otherwise be interpreted as an invalid option. If you do insert ``--`` before the expression it will cause option scanning to stop just like for every other command and it won't be part of the expression.
docs: Add labels to all commands This allows us to use :ref: references, which don't require hardcoding it as html [ci skip] 2019-03-31 17:05:09 +08:00			`.. _cmd-math:`

doc: homogenize commands titles 2020-03-31 23:37:38 +08:00			`math - perform mathematics calculations`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`=======================================`
Switch command docs from \section to reStructuredText 2018-12-17 09:39:33 +08:00
Migrate the 'synopsis' sections to .rst format 2018-12-18 09:58:24 +08:00			`Synopsis`
			`--------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
docs: update all command synopsis formatting Adds synopses for those commands missing them. Moves all synopsis sections to code blocks. This improves the appearance, although highlighting as fish code may not be the ideal appearance. 2019-09-17 17:59:04 +08:00			`::`

			`math [-sN \| --scale=N] [--] EXPRESSION`
Migrate the 'synopsis' sections to .rst format 2018-12-18 09:58:24 +08:00
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Description`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`-----------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math`` is used to perform mathematical calculations. It supports all the usual operations such as addition, subtraction, etc. As well as functions like ``abs()``, ``sqrt()`` and ``log2()``.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			By default, the output is as a float with trailing zeroes trimmed. To get a fixed representation, the ``--scale`` option can be used, including ``--scale=0`` for integer output.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Fix typo (verb clarification) in math.rst Was: "parameter expansion takes before expressions are evaluated." Now: "parameter expansion happens before expressions are evaluated." I suspect the original intent was to use "takes place," but I see "happens" as less idiomatic and therefore may benefit non-English-native users. 2020-08-19 07:56:57 +08:00			Keep in mind that parameter expansion happens before expressions are evaluated. This can be very useful in order to perform calculations involving shell variables or the output of command substitutions, but it also means that parenthesis (``()``) and the asterisk (``*``) glob character have to be escaped or quoted. ``x`` can also be used to denote multiplication, but it needs to be followed by whitespace to distinguish it from hexadecimal numbers.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math`` ignores whitespace between arguments and takes its input as multiple arguments (internally joined with a space), so ``math 2 +2`` and ``math "2 + 2"`` work the same. ``math 2 2`` is an error.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
			`The following options are available:`

Incorporate most new doc changes since branch Adds most documentation changes since 72c0213d42b77b2f01223b5515669840110ea9b9 2019-02-25 07:01:16 +08:00			- ``-sN`` or ``--scale=N`` sets the scale of the result. ``N`` must be an integer or the word "max" for the maximum scale. A scale of zero causes results to be rounded down to the nearest integer. So ``3/2`` returns ``1`` rather than ``2`` which ``1.5`` would normally round to. This is for compatibility with ``bc`` which was the basis for this command prior to fish 3.0.0. Scale values greater than zero causes the result to be rounded using the usual rules to the specified number of decimal places.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Return Values`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`-------------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			If the expression is successfully evaluated and doesn't over/underflow or return NaN the return ``status`` is zero (success) else one.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Syntax`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math`` knows some operators, constants, functions and can (obviously) read numbers.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			For numbers, ``.`` is always the radix character regardless of locale - ``2.5``, not ``2,5``. Scientific notation (``10e5``) is also available.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Operators`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`---------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math`` knows the following operators:
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			- ``+`` for addition and ``-`` for subtraction.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
math: Allow "x" for multiplication It's always a bit annoying that `*` requires quoting. So we allow "x" as an alternative, only it needs to be followed by whitespace to distinguish it from "0x" hexadecimal notation. 2019-05-30 22:00:45 +08:00			- ```` or ``x`` for multiplication, ``/`` for division. (Note that ```` is the glob character and needs to be quoted or escaped, ``x`` needs to be followed by whitespace or it looks like ``0x`` hexadecimal notation.)
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			- ``^`` for exponentiation.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			- ``%`` for modulo.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Incorporate most new doc changes since branch Adds most documentation changes since 72c0213d42b77b2f01223b5515669840110ea9b9 2019-02-25 07:01:16 +08:00			- ``(`` and ``)`` for grouping. (These need to be quoted or escaped because ``()`` denotes a command substitution.)
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			They are all used in an infix manner - ``5 + 2``, not ``+ 5 2``.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Constants`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`---------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math`` knows the following constants:
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			- ``e`` - Euler's number.
			- ``pi`` - You know that one. Half of Tau. (Tau is not implemented)
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			Use them without a leading ``$`` - ``pi - 3`` should be about 0.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Functions`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`---------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math`` supports the following functions:

			- ``abs``
			- ``acos``
			- ``asin``
			- ``atan``
			- ``atan2``
math: Add bitwise and/or functions Just as `math "bitand(5,3)"` and `math "bitor(6,2)"`. These cast to long long before doing their thing, so they truncate to an integer, producing weird results with floats. That's to be expected because float representation is very different, and performing bitwise operations on floats feels quite useless. Fixes #7281. 2020-08-25 22:45:31 +08:00			- ``bitand``, ``bitor`` and ``bitxor`` to perform bitwise operations. These will throw away any non-integer parts and interpret the rest as an int.
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			- ``ceil``
			- ``cos``
			- ``cosh``
			- ``exp`` - the base-e exponential function
			- ``fac`` - factorial
			- ``floor``
			- ``ln``
			- ``log`` or ``log10`` - the base-10 logarithm
			- ``ncr``
			- ``npr``
			- ``pow(x,y)`` returns x to the y (and can be written as ``x ^ y``)
			- ``round`` - rounds to the nearest integer, away from 0
			- ``sin``
			- ``sinh``
			- ``sqrt``
			- ``tan``
			- ``tanh``
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
			`All of the trigonometric functions use radians.`

Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Examples`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`--------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math 1+1`` outputs 2.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math $status - 128`` outputs the numerical exit status of the last command minus 128.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math 10 / 6`` outputs ``1.666667``.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math -s0 10.0 / 6.0`` outputs ``1``.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math -s3 10 / 6`` outputs ``1.666``.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			``math "sin(pi)"`` outputs ``0``.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Incorporate most new doc changes since branch Adds most documentation changes since 72c0213d42b77b2f01223b5515669840110ea9b9 2019-02-25 07:01:16 +08:00			``math 5 \* 2`` or ``math "5 * 2"`` or ``math 5 "*" 2`` all output ``10``.

math: Allow "x" for multiplication It's always a bit annoying that `*` requires quoting. So we allow "x" as an alternative, only it needs to be followed by whitespace to distinguish it from "0x" hexadecimal notation. 2019-05-30 22:00:45 +08:00			``math 0xFF`` outputs 255, ``math 0 x 3`` outputs 0 (because it computes 0 multiplied by 3).

math: Add bitwise and/or functions Just as `math "bitand(5,3)"` and `math "bitor(6,2)"`. These cast to long long before doing their thing, so they truncate to an integer, producing weird results with floats. That's to be expected because float representation is very different, and performing bitwise operations on floats feels quite useless. Fixes #7281. 2020-08-25 22:45:31 +08:00			``math "bitand(0xFE, 0x2e)"`` outputs 46.

			``math "bitor(9,2)"`` outputs 11.

Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Compatibility notes`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`-------------------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			Fish 1.x and 2.x releases relied on the ``bc`` command for handling ``math`` expressions. Starting with fish 3.0.0 fish uses the tinyexpr library and evaluates the expression without the involvement of any external commands.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Switch backticks to double backticks for rst compatibility 2018-12-20 04:02:45 +08:00			You don't need to use ``--`` before the expression even if it begins with a minus sign which might otherwise be interpreted as an invalid option. If you do insert ``--`` before the expression it will cause option scanning to stop just like for every other command and it won't be part of the expression.