65 lines
2.8 KiB
Plaintext
65 lines
2.8 KiB
Plaintext
created: 20190206140446821
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modified: 20230321133008898
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tags: Filters
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title: Mathematics Operators
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type: text/vnd.tiddlywiki
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<<.from-version "5.1.20">>The mathematics filter operators allow numerical calculations to be performed within filters.
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! Using mathematics operators
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The mathematics operators interpret their arguments as numbers according to the following rules:
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* Any non-numeric characters after a valid number are ignored (e.g. `28px` is interpreted as the number 28)
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* If the argument cannot be interpreted as a number, the value 0 is used (e.g. `foo` is interpreted as the number 0)
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* The special values `Infinity` and `-Infinity` can be used to represent positive and negative infinity respectively
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<$macrocall $name=".warning" _="Some filter operators remove duplicate items which can cause unexpected results when using the mathematics operators. See [[Dominant Append]] for details."/>
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The mathematics operators take three different forms:
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* ''Unary operators'' apply an operation to each number in the input list (e.g. negate, truncate, sign)
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** <<.inline-operator-example "=1 =2 =3 =4 +[negate[]]">>
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** <<.inline-operator-example "=1.2 =2.4 =3.6 =4.8 +[trunc[]]">>
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** <<.inline-operator-example "=1.2 =2.4 =3.6 =4.8 +[round[]]">>
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* ''Binary operators'' apply an operation and parameter to each number in the input list (e.g. add, multiply, remainder)
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** <<.inline-operator-example "=1 =2 =3 =4 +[add[3]]">>
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** <<.inline-operator-example "=1 =2 =3 =4 +[multiply[8]]">>
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* ''Reducing operators'' apply an operation to all of the numbers in the input list, returning a single result (e.g. sum, product)
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** <<.inline-operator-example "=1 =2 =3 =4 +[sum[]]">>
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** <<.inline-operator-example "=1 =2 =3 =4 +[product[]]">>
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** <<.inline-operator-example "=1 =2 =3 =4 +[average[]]">>
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! Operations Combination
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Operations can be combined by concatenating them while merging the inner `][` characters.
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* <<.inline-operator-example "[[355]divide[113]fixed[5]]">>
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* <<.inline-operator-example "[range[100]sum[]divide[100]]">>
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* <<.inline-operator-example "[tag[HelloThere]get[text]length[]sum[]]">>
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Complex operations will sometimes need to be split up into separate filters. For example, to compute the average length of the text field of tiddlers tagged "~HelloThere":
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<$macrocall $name='wikitext-example-without-html'
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src="""<$set name="number-of-tiddlers" value={{{ [tag[HelloThere]count[]] }}}>
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Average length of <$text text=<<number-of-tiddlers>>/> tiddlers tagged <<tag "HelloThere">>: <$text text={{{ [tag[HelloThere]get[text]length[]sum[]divide<number-of-tiddlers>fixed[3]] }}}/>
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</$set>""" />
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! Mathematics Operators list
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<table>
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<tr>
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<th align="left">Operator</th>
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<th align="left">Purpose</th>
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</tr>
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<$list filter="[tag[Mathematics Operators]sort[caption]]">
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<tr>
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<td><$link>{{!!caption}}</$link></td>
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<td>{{!!op-purpose}}</td>
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</tr>
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</$list>
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</table>
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