C#•2d ago

Stackalloc a span of tuples?

Is it possible to stackalloc a span of tuples like this? Span<(object, string)> foos = stackalloc (object, string)[12];

10 Replies

MODiX•2d ago

Zeth

REPL Result: Success

void M() {
  Span<(int, int)> a = stackalloc (int, int)[1];
}

void M() {
  Span<(int, int)> a = stackalloc (int, int)[1];
}

Compile: 306.049ms | Execution: 28.801ms | React with ❌ to remove this embed.

zacoonsOP•2d ago

gotcha

Jimmacle•2d ago

does additionalSources have a small bounded length?

zacoonsOP•2d ago

not bounded, but generally quite small, yeah it's just a helper fn for multi binding

cap5lut•2d ago

if u have a small maximum u can use an inline array

[InlineArray(16)]
public struct Buffer16<T>
{
  private T _element0;
}

[InlineArray(16)]
public struct Buffer16<T>
{
  private T _element0;
}

and use that

Span<(object, string)> span = new Buffer16<(object, string)>(); // cant remember if u have to cast or use a method here to get it as span
span = span[..actualLength];
// do something

Span<(object, string)> span = new Buffer16<(object, string)>(); // cant remember if u have to cast or use a method here to get it as span
span = span[..actualLength];
// do something

generally u shouldnt use unbound stack allocations. constants are safe and fast dynamic and bound to an upper limit are safe but not that fast. dynamic and unbound is not that fast and dangerous. so if u go over some maximum, u should either allocate an array or use an array pool as fallback

Petris•2d ago

or just

Span<(object, string)> s = [default, default, default, default, default, default, default, default, default, default, default, default, default, default, default, default];

Span<(object, string)> s = [default, default, default, default, default, default, default, default, default, default, default, default, default, default, default, default];

cap5lut•2d ago

didnt know that, tho i would still go with the buffer apprach than with this mess >.<

Petris•2d ago

well that uses an inlinearray i wish there was some syntax for it

cap5lut•2d ago

seems like this does as well, and even has a lot of assignments for that: https://sharplab.io/#v2:D4AQTAjAsAUCDMACciDCiDetE+UkALIgLIAUAlJtrjQMoAOAhgHYA8pA9gEYBWApgGMALgBpkEAAzkAfIgDOiALyIA2gBM+AM0YBXADajEG7fsPHdBsedNWtFs3ZtHHl5ydfWPLh+5/3bvgH+bsGeQgC6ANzUOAC+sLFAA==

SharpLab

C#/VB/F# compiler playground.

Petris•2d ago

yeah I've meant my versioon hmm with the assignments maybe somebody should open a #roslyn issue to skip assigning with default

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Stackalloc a span of tuples?

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