Clamping Values

[Mike Jones]

Is there some kind of template way to convert a value, say int, to meet a universal like {n:int | n > 3; n < 6} ?

Mainly to avoid writing functions for these cases. min/max functions clamp the value, but don't deal with the quantifier. 

Perhaps what I am looking for is a template that generates the quantifier, or perhaps that is a macro and one already exists?

[Hongwei Xi]

fun{}
clamp
  {l,u:int | l <= u}
(
  l: int(l), x: int, u: int(u)
) : intBtwe(l,u) =
  let val x = g1ofg0(x) in min(max(l, x), u) end

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[Brandon Barker]

I think, if I understand correctly, there are a lot like this. Here's
the one for your case:
https://github.com/githwxi/ATS-Postiats/search?utf8=✓&q=intBtw

On Tue, Nov 3, 2015 at 8:30 PM, Mike Jones <proc...@gmail.com> wrote:

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[Mike Jones]

Related to min/max clamping, what does this do:

val x: uint16 = cast{uint16}(5)
val y: uint8 = cast{uint8}(x)

Does it actually copy memory from a uint16_t to a uint8_t? Does it just take the least significant byte? Does it reuse memory? Does it just play a dangerous pointer game?

[gmhwxi]

A type in C is just like shoe size.

In the following code, both x and y are values:

val x: uint16 = cast{uint16}(5)
val y: uint8 = cast{uint8}(x)

Most likely, the C compiler is to replace x and y with the constant 5
in this particular case.

>>Does it actually copy memory from a uint16_t to a uint8_t?

It could but it is very unlikely. Compilers like gcc and clang are very good
at performing all sorts of optimizations. I could not think of anything dangerous
in this case.

[gmhwxi]

Say you write the following code in C:

uint16_t x = 5;
  uint8_t y = x;

Casting is implicitly done. It is really equivalent to writing:

uint16_t x = (uint16_t)5;
  uint8_t y =  (uint8_t)x;

In ATS casting needs to be done explicitly.

On Tuesday, November 3, 2015 at 10:01:50 PM UTC-5, Mike Jones wrote: