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32a2bea7f5
Include = before each number in the Mathematics Operators examples, so that people get used to seeing that in math examples where dupes are likely. Only the Mathematics Operators tiddler really needed to be changed; the example tiddlers for individual operators were already using =. Fixes #3979.
44 lines
2.4 KiB
Plaintext
44 lines
2.4 KiB
Plaintext
created: 20190206140446821
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modified: 20190611155838557
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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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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 operand 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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Operators can be combined:
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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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<<list-links "[tag[Mathematics Operators]]">>
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