4 ms·

Yeah - plus Javascript doesn't even support 32 bit integers.

by ClassyJacket 7y ago

GordonS 7y ago
Eh? What exactly is JavaScript's numeric type then? I always presumed it was a 32-bit, signed integer..
- xtian 7y ago
  https://developer.mozilla.org/en-US/docs/Glossary/Number https://developer.mozilla.org/en-US/docs/Glossary/Number
- vbezhenar 7y ago
  JavaScript uses double. Though its precision is more than enough to support 32 bits. Actually it supports 53 bits for integers, then it gets imprecise.
  - ska 7y ago
    lua does the same thing. It's not crazy.
    - rayiner 7y ago
      Failing to distinguish between integer and floating point types is crazy. Not as crazy as TCL’s everything being a strong, but not the work of a mentally well person.
      - nine_k 7y ago
        It's a work of RAM-constrained and time-constrained people in early 1990s, following approaches developed on 1970s for Lisp. Packing as much as possible into a single cons cell, or a JS value, was (and is) important, so bit masking to distinguish between integers, floats, strings, functions, objects, was an inevitable approach.
        rayiner 7y ago
        Lisp has distinct integer and floating point types with the correct behavior for those types. At runtime they might get passed around as tagged data, but that’s not visible in the language semantics. In JavaScript, by contrast, the language exposes only a double float rule and you have to use floats where you’d otherwise use integers.
        nine_k 7y ago
        I agree. A Lisp may not make available all bits of a machine word to an integer, but they won't mix up an integer and a float. JavaScript tried to make things artificially "simpler" by implicit conversions. As usual, the lack of consistency only lead to more eventual complexity than a sound solution would have in the first place.
      - camgunz 7y ago
        "Numbers" actually conceal a lot of complexity. Is 2 between 1.9 and 2.1? What about between 1.9 and 2.1111111111111111111111111111111111111111? What about over/underflow? Do you wrap, clamp, throw an exception? Do you round or set +-inf? Can you divide by zero? Can you divide an integer by a floating point number, and if so what would the result be? What happens if, say, you multiply an 8-bit and 16-bit integer and the result (using twos complement) doesn't fit in 8 bits? "Use IEEE-754 doubles for everything" answers all these questions. I think JavaScript is basically junk, but I find at least this aspect to be rather elegant (to the point that I suspect it came from somewhere else, haha).
    - wahern 7y ago
      Lua 5.3 added 64-bit integers along with native bitwise operators. There's no end of bickering on the mailing-list over the finer details, but without a doubt 64-bit integers is a win.
      - AlexMax 7y ago
        > without a doubt 64-bit integers is a win I'm not so sure about that. There is an alternative implementation of Lua called LuaJIT, which uses a similar NaN-tagging trick, and it also happens to be incredibly fast. LuaJIT uses the 5.1 version of the language, with some backported 5.2 features for compatibility, but it will likely never backport 64-bit integers from 5.3. It's resulted in something like the Python 2/3 split. Except it's even worse because Lua has relatively little penetration as a general purpose scripting language, but is quite popular as a language that can be embedded in a program to add scripting capabilities. This means it's up to the developer of said program which version of Lua they choose to embed, and from what I can tell, most developers choose speed over 64-bit integer support.
- Stratoscope 7y ago
  > What exactly is JavaScript's numeric type then? I always presumed it was a 32-bit, signed integer. It's not ideal to presume such a thing when there are ways to find out the answer, either from the link in a sibling comment or by observing JavaScript code that uses the Google Maps API or similar mapping APIs. How would you represent a latitude or longitude with a 32-bit integer? I don't mean to pick on you. I have made these same kinds of assumptions too many times and it always got me in trouble. Here's a particularly embarrassing example. When I did my first election results map for Google, I needed a way to represent the outline of a state. I saw that the Maps API supported polygons, so I thought "that's great, I can use a polygon for each state!" Until the map went live and someone asked me "What happened to the northern part of Michigan [which isn't connected to the rest of the state]? And where are the rest of the Hawaiian Islands?" It turned out that a single polygon wasn't enough to represent the outline of a state. Who would have guessed? Don't let this happen to you. :-)
batmansmk 7y ago
You are right. We can store and manipulate Int32 arrays as a typedarrays. The arithmetic is limited to a few operations.
vanderZwan 7y ago
The implementations usually do (in the sense of optimizing them)
- kevingadd 7y ago
  v8 only has 31-bit 'SMI' and not 32-bit ints, iirc.
  - gsnedders 7y ago
    Correct, but it is the only one to do so.
  - cztomsik 7y ago
    on 64bit archs it is 32bit https://github.com/thlorenz/v8-perf/blob/master/data-types.md#efficiently-representing-values-and-tagging https://github.com/thlorenz/v8-perf/blob/master/data-types.m...

Yeah - plus Javascript doesn't even support 32 bit integers.

GordonS 7y ago

Eh? What exactly is JavaScript's numeric type then? I always presumed it was a 32-bit, signed integer..

xtian 7y ago
https://developer.mozilla.org/en-US/docs/Glossary/Number https://developer.mozilla.org/en-US/docs/Glossary/Number
vbezhenar 7y ago
JavaScript uses double. Though its precision is more than enough to support 32 bits. Actually it supports 53 bits for integers, then it gets imprecise.
- ska 7y ago
  lua does the same thing. It's not crazy.
  - rayiner 7y ago
    Failing to distinguish between integer and floating point types is crazy. Not as crazy as TCL’s everything being a strong, but not the work of a mentally well person.
    - nine_k 7y ago
      It's a work of RAM-constrained and time-constrained people in early 1990s, following approaches developed on 1970s for Lisp. Packing as much as possible into a single cons cell, or a JS value, was (and is) important, so bit masking to distinguish between integers, floats, strings, functions, objects, was an inevitable approach.
      - rayiner 7y ago
        Lisp has distinct integer and floating point types with the correct behavior for those types. At runtime they might get passed around as tagged data, but that’s not visible in the language semantics. In JavaScript, by contrast, the language exposes only a double float rule and you have to use floats where you’d otherwise use integers.
        nine_k 7y ago
        I agree. A Lisp may not make available all bits of a machine word to an integer, but they won't mix up an integer and a float. JavaScript tried to make things artificially "simpler" by implicit conversions. As usual, the lack of consistency only lead to more eventual complexity than a sound solution would have in the first place.
    - camgunz 7y ago
      "Numbers" actually conceal a lot of complexity. Is 2 between 1.9 and 2.1? What about between 1.9 and 2.1111111111111111111111111111111111111111? What about over/underflow? Do you wrap, clamp, throw an exception? Do you round or set +-inf? Can you divide by zero? Can you divide an integer by a floating point number, and if so what would the result be? What happens if, say, you multiply an 8-bit and 16-bit integer and the result (using twos complement) doesn't fit in 8 bits? "Use IEEE-754 doubles for everything" answers all these questions. I think JavaScript is basically junk, but I find at least this aspect to be rather elegant (to the point that I suspect it came from somewhere else, haha).
  - wahern 7y ago
    Lua 5.3 added 64-bit integers along with native bitwise operators. There's no end of bickering on the mailing-list over the finer details, but without a doubt 64-bit integers is a win.
    - AlexMax 7y ago
      > without a doubt 64-bit integers is a win I'm not so sure about that. There is an alternative implementation of Lua called LuaJIT, which uses a similar NaN-tagging trick, and it also happens to be incredibly fast. LuaJIT uses the 5.1 version of the language, with some backported 5.2 features for compatibility, but it will likely never backport 64-bit integers from 5.3. It's resulted in something like the Python 2/3 split. Except it's even worse because Lua has relatively little penetration as a general purpose scripting language, but is quite popular as a language that can be embedded in a program to add scripting capabilities. This means it's up to the developer of said program which version of Lua they choose to embed, and from what I can tell, most developers choose speed over 64-bit integer support.
Stratoscope 7y ago
> What exactly is JavaScript's numeric type then? I always presumed it was a 32-bit, signed integer. It's not ideal to presume such a thing when there are ways to find out the answer, either from the link in a sibling comment or by observing JavaScript code that uses the Google Maps API or similar mapping APIs. How would you represent a latitude or longitude with a 32-bit integer? I don't mean to pick on you. I have made these same kinds of assumptions too many times and it always got me in trouble. Here's a particularly embarrassing example. When I did my first election results map for Google, I needed a way to represent the outline of a state. I saw that the Maps API supported polygons, so I thought "that's great, I can use a polygon for each state!" Until the map went live and someone asked me "What happened to the northern part of Michigan [which isn't connected to the rest of the state]? And where are the rest of the Hawaiian Islands?" It turned out that a single polygon wasn't enough to represent the outline of a state. Who would have guessed? Don't let this happen to you. :-)

batmansmk 7y ago

You are right. We can store and manipulate Int32 arrays as a typedarrays. The arithmetic is limited to a few operations.

vanderZwan 7y ago

The implementations usually do (in the sense of optimizing them)

kevingadd 7y ago
v8 only has 31-bit 'SMI' and not 32-bit ints, iirc.
- gsnedders 7y ago
  Correct, but it is the only one to do so.
- cztomsik 7y ago
  on 64bit archs it is 32bit https://github.com/thlorenz/v8-perf/blob/master/data-types.md#efficiently-representing-values-and-tagging https://github.com/thlorenz/v8-perf/blob/master/data-types.m...