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Feb 9, 2020
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doc(inline): improve recursive example #8235

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doc(inline): improve recursive example
robstoll Feb 7, 2020
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doc(inline): typeo usualy instead of usually
robstoll Feb 8, 2020
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doc(inline): show inline can result in larger code
robstoll Feb 8, 2020
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21 changes: 12 additions & 9 deletions docs/docs/reference/metaprogramming/inline.md
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Expand Up @@ -121,23 +121,26 @@ power(expr, 10)
```

Parameters of inline methods can have an `inline` modifier as well. This means
that actual arguments to these parameters will be inlined in the body of the `inline def`.
`inline` parameter have call semantics equivalent to by-name parameters but allows for duplication
of the code in the argument. It is usualy useful constant values need to be propagated to allow
further optimizations/reductions.
that actual arguments to these parameters will be inlined in the body of the
`inline def`. `inline` parameters have call semantics equivalent to by-name parameters
but allow for duplication of the code in the argument. It is usually useful when constant
values need to be propagated to allow further optimizations/reductions.

The following example shows the difference in translation between by-value, by-name and `inline`
parameters:

```scala
inline def sumTwice(a: Int, b: =>Int, inline c: Int) = a + a + b + b + c + c
inline def funkyAssertEquals(actual: Double, expected: =>Double, inline delta: Double): Unit =
if (actual - expected).abs > delta then
throw new AssertionError(s"difference between ${expected} and ${actual} was larger than ${delta}")

sumTwice(f(), g(), h())
funkyAssertEquals(computeActual(), f() + g(), h() + i() - j())
// translates to
//
// val a = f()
// def b = g()
// a + a + b + b + h() + h()
// val actual = computeActual()
// def expected = f() + g()
// if (actual - expected).abs > h() + i() - j() then
// throw new AssertionError(s"difference between ${expected} and ${actual} was larger than ${h() + i() - j()}")
```

### Relationship to @inline
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