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Correct math docs

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This was an oversight when math was changed to default to float output.

Also some more jokey stuff. Jokey stuff is nice.
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Fabian Homborg 2018-09-15 15:31:59 +02:00
parent 9be7288fab
commit bda147c7d3
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doc_src/math.txt
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@ -7,13 +7,17 @@ math [-sN | --scale=N] [--] EXPRESSION
\subsection math-description 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()`. Internally all calculations are performed using floating point representation. Integer values are first converted to floating point before being used. The default output format is integer which causes floating point results to be rounded down to the nearest integer. The `--scale` option can be used to get floating point output.
`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 takes 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.
`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 and defaults to zero. 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.
- `-sN` or `--scale=N` sets the scale of the result. `N` must be an integer. 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.
\subsection return-values Return Values
@ -46,9 +50,9 @@ They are all used in an infix manner - `5 + 2`, not `+ 5 2`.
`math` knows the following constants:
- `e` - Euler's number.
- `pi` - You know that one. Half of Tau.
- `pi` - You know that one. Half of Tau. (Tau is not implemented)
Use them without a leading `$`.
Use them without a leading `$` - `pi - 3` should be about 0.
\subsection math-functions Functions
@ -84,7 +88,7 @@ All of the trigonometric functions use radians.
`math $status - 128` outputs the numerical exit status of the last command minus 128.
`math 10 / 6` outputs `1`.
`math 10 / 6` outputs `1.666667`.
`math -s0 10.0 / 6.0` outputs `1`.
@ -97,5 +101,3 @@ All of the trigonometric functions use radians.
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.
Note that the modulo operator (`x % y`) is not well defined for floating point arithmetic. Fish rounds down all floating point values to the nearest integer before performing the modulo operation. So `10.5 % 6.1` is `4`, regardless of what `--scale` value is in effect.