Editorial: Introduce an operation for backing To{Int,Uint}{8,16,32} and To{BigInt,BigUint}64 #3832
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@@ -5316,6 +5316,30 @@ <h1> | |||||
| </emu-note> | ||||||
| </emu-clause> | ||||||
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| <emu-clause id="sec-tofixedsizeinteger" type="abstract operation"> | ||||||
| <h1> | ||||||
| ToFixedSizeInteger ( | ||||||
| _int_: an integer, +∞, or -∞, | ||||||
| _signed_: ~unsigned~ or ~signed~, | ||||||
| _bitWidth_: a positive integer, | ||||||
| ): an integer | ||||||
| </h1> | ||||||
| <dl class="header"> | ||||||
| <dt>description</dt> | ||||||
| <dd>It maps _int_ to one of 2<sup>_bitWidth_</sup> integers in the inclusive interval from 0 to 2<sup>_bitWidth_</sup> - 1 (if _signed_ is ~unsigned~) or -2<sup>_bitWidth_ - 1</sup> to 2<sup>_bitWidth_ - 1</sup> - 1 (if _signed_ is ~signed~).</dd> | ||||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. If _int_ is +∞ or -∞, return 0. | ||||||
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Collaborator
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Suggested change
(editorial convention)
Collaborator
There was a problem hiding this comment. To be clear (despite GitHub bug), my suggestion is to insert "either".
Member
Author
There was a problem hiding this comment. I find the comparison conventions terribly confusing/incomplete and possibly contradictory, but since int is a mathematical value, shouldn't this actually be
Collaborator
There was a problem hiding this comment. Technically, it's an 'extended mathematical value', which the comparison conventions don't mention, but lumping it in with mathematical values would be reasonable. So yeah, using |
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| 1. Let _fixedInt_ be _int_ modulo 2<sup>_bitWidth_</sup>. | ||||||
| 1. NOTE: The following step does not change the two's complement representation of _fixedInt_. | ||||||
| 1. If _signed_ is ~signed~ and _fixedInt_ ≥ 2<sup>_bitWidth_ - 1</sup>, set _fixedInt_ to _fixedInt_ - 2<sup>_bitWidth_</sup>. | ||||||
| 1. Return _fixedInt_. | ||||||
| </emu-alg> | ||||||
| <emu-note> | ||||||
| <p>ToFixedSizeInteger is idempotent: for any ECMAScript language value _x_, ToFixedSizeInteger(ToFixedSizeInteger(_x_, _signed_, _bitWidth_), _signed_, _bitWidth_) is the same as ToFixedSizeInteger(_x_, _signed_, _bitWidth_). In fact, because +∞ and -∞ are mapped to 0, this invariant even survives inversion of _signed_ (e.g., ToFixedSizeInteger(ToFixedSizeInteger(_x_, ~signed~, 32), ~unsigned~, 32) is the same as ToFixedSizeInteger(_x_, ~unsigned~, 32)).</p> | ||||||
| </emu-note> | ||||||
| </emu-clause> | ||||||
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| <emu-clause id="sec-toint32" type="abstract operation"> | ||||||
| <h1> | ||||||
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Contributor
There was a problem hiding this comment. I'd prefer us to retain something like the example from the old note. Something like |
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| ToInt32 ( | ||||||
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@@ -5324,29 +5348,12 @@ <h1> | |||||
| </h1> | ||||||
| <dl class="header"> | ||||||
| <dt>description</dt> | ||||||
| <dd>It converts _argument_ to one of 2<sup>32</sup> integral Number values in the inclusive interval from 𝔽(-2<sup>31</sup>) to 𝔽(2<sup>31</sup> - 1), excluding *-0*<sub>𝔽</sub>.</dd> | ||||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. Let _int_ be ? ToIntegerOrInfinity(_argument_). | ||||||
| 1. Return 𝔽(ToFixedSizeInteger(_int_, ~signed~, 32)). | ||||||
| </emu-alg> | ||||||
| </emu-clause> | ||||||
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| <emu-clause id="sec-touint32" type="abstract operation"> | ||||||
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@@ -5361,27 +5368,8 @@ <h1> | |||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. Let _int_ be ? ToIntegerOrInfinity(_argument_). | ||||||
| 1. Return 𝔽(ToFixedSizeInteger(_int_, ~unsigned~, 32)). | ||||||
| </emu-alg> | ||||||
| </emu-clause> | ||||||
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| <emu-clause id="sec-toint16" type="abstract operation"> | ||||||
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@@ -5392,14 +5380,11 @@ <h1> | |||||
| </h1> | ||||||
| <dl class="header"> | ||||||
| <dt>description</dt> | ||||||
| <dd>It converts _argument_ to one of 2<sup>16</sup> integral Number values in the inclusive interval from 𝔽(-2<sup>15</sup>) to 𝔽(2<sup>15</sup> - 1), excluding *-0*<sub>𝔽</sub>.</dd> | ||||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. Let _int_ be ? ToIntegerOrInfinity(_argument_). | ||||||
| 1. Return 𝔽(ToFixedSizeInteger(_int_, ~signed~, 16)). | ||||||
| </emu-alg> | ||||||
| </emu-clause> | ||||||
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@@ -5415,21 +5400,8 @@ <h1> | |||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. Let _int_ be ? ToIntegerOrInfinity(_argument_). | ||||||
| 1. Return 𝔽(ToFixedSizeInteger(_int_, ~unsigned~, 16)). | ||||||
| </emu-alg> | ||||||
| </emu-clause> | ||||||
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| <emu-clause id="sec-toint8" type="abstract operation"> | ||||||
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@@ -5440,14 +5412,11 @@ <h1> | |||||
| </h1> | ||||||
| <dl class="header"> | ||||||
| <dt>description</dt> | ||||||
| <dd>It converts _argument_ to one of 2<sup>8</sup> integral Number values in the inclusive interval from *-128*<sub>𝔽</sub> to *127*<sub>𝔽</sub>, excluding *-0*<sub>𝔽</sub>.</dd> | ||||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. Let _int_ be ? ToIntegerOrInfinity(_argument_). | ||||||
| 1. Return 𝔽(ToFixedSizeInteger(_int_, ~signed~, 8)). | ||||||
| </emu-alg> | ||||||
| </emu-clause> | ||||||
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@@ -5463,9 +5432,7 @@ <h1> | |||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. Let _int_ be ? ToIntegerOrInfinity(_argument_). | ||||||
| 1. Return 𝔽(ToFixedSizeInteger(_int_, ~unsigned~, 8)). | ||||||
| </emu-alg> | ||||||
| </emu-clause> | ||||||
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@@ -5640,10 +5607,8 @@ <h1> | |||||
| <dd>It converts _argument_ to one of 2<sup>64</sup> BigInt values in the inclusive interval from ℤ(-2<sup>63</sup>) to ℤ(2<sup>63</sup> - 1).</dd> | ||||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. Let _int_ be ℝ(? ToBigInt(_argument_)). | ||||||
| 1. Return ℤ(ToFixedSizeInteger(_int_, ~signed~, 64)). | ||||||
| </emu-alg> | ||||||
| </emu-clause> | ||||||
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@@ -5658,9 +5623,8 @@ <h1> | |||||
| <dd>It converts _argument_ to one of 2<sup>64</sup> BigInt values in the inclusive interval from *0*<sub>ℤ</sub> to ℤ(2<sup>64</sup> - 1).</dd> | ||||||
| </dl> | ||||||
| <emu-alg> | ||||||
| 1. Let _int_ be ℝ(? ToBigInt(_argument_)). | ||||||
| 1. Return ℤ(ToFixedSizeInteger(_int_, ~unsigned~, 64)). | ||||||
| </emu-alg> | ||||||
| </emu-clause> | ||||||
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Since this now performs no type conversion, "IntegerToFixedSize" might be a better name. Opinions are welcome.