3936017f10
* Replace tag type with tagIdent and tagDecl Signed-off-by: Nick Cameron <nrc@ncameron.org> * Replace tagIdent with TaggedEdge and TaggedFace Signed-off-by: Nick Cameron <nrc@ncameron.org> --------- Signed-off-by: Nick Cameron <nrc@ncameron.org>
41 lines
107 KiB
Markdown
41 lines
107 KiB
Markdown
---
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title: "PI"
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subtitle: "Constant in std::math"
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excerpt: "The value of `pi`, Archimedes’ constant (π)."
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layout: manual
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---
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The value of `pi`, Archimedes’ constant (π).
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```kcl
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PI: number(_?) = 3.14159265358979323846264338327950288_?
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```
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`PI` is a number and is technically a ratio, so you might expect it to have type [`number(_)`](/docs/kcl-std/types/std-types-number).
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However, `PI` is nearly always used for converting between different units - usually degrees to or
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from radians. Therefore, `PI` is treated a bit specially by KCL and always has unknown units. This
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means that if you use `PI`, you will need to give KCL some extra information about the units of numbers.
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Usually you should use type ascription on the result of calculations, e.g., `(2 * PI): number(rad)`.
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It is better to use `units::toRadians` or `units::toDegrees` to convert between angles with
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different units where possible.
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### Type
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[`number(_?)`](/docs/kcl-std/types/std-types-number) - A number.
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### Examples
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```kcl
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circumference = 70
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exampleSketch = startSketchOn(XZ)
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|> circle(center = [0, 0], radius = (circumference / (2 * PI)): number(mm))
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example = extrude(exampleSketch, length = 5)
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```
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