Function documentation and syntax - ECMA262

Question

Help me where I can find documentation for the TO_NUMBER function and what does the %(percentage sign) mean when placed before MathExpRT (which also can't find any docs about it)

https://github.com/v8/v8/blob/b0e4dce6091a8777bda80d962df76525dc6c5ea9/src/js/math.js#L62-L64

score 0 · Answer 1 · edited May 23 '17 at 10:27

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% in this context is a V8-specific syntax to denote a C++ method call, see here and here (it's not a JavaScript % which is a modulo operator).

MathExpRT as far as I understand from the other answers, is a name of a C++ method (in V8 runtime) to be called from within the JS file you linked.

edited May 23 '17 at 10:27

Community

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answered Oct 16 '16 at 18:43

jakub.g

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And `TO_NUMBER` ? How can I see the source code ? – Mark Spencer Oct 16 '16 at 18:48
Thanks........... – Mark Spencer Oct 16 '16 at 20:45

score 0 · Accepted Answer · answered Oct 16 '16 at 20:23

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TO_NUMBER is a V8-internal macro defined here:

https://github.com/v8/v8/blob/ac886b0c1c173d6ceff762952e1d6cf78e8bd172/src/js/macros.py#L96

Not that this will help you much: it simply calls into an intrinsic, which is implemented as generated code, and has many different implementations depending on compiler (V8 has four), hardware platform (V8 supports about 10), and available type information. One generic code generator can be seen here:

https://github.com/v8/v8/blob/5acc31d86329794407f2764a369c2f638305b376/src/code-stub-assembler.cc#L3259

If you just want to know the semantics, you better look at the ECMAScript 262 standard.

answered Oct 16 '16 at 20:23

Andreas Rossberg

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thank you very much, but ahh this code seems so intentionally obfuscated... – Mark Spencer Oct 16 '16 at 20:45
@MarkSpencer, it's a code generator -- for that it is actually pretty readable. ;) – Andreas Rossberg Oct 17 '16 at 06:18
what do you mean by a code generator ? like babel (which is for js)? – Mark Spencer Oct 17 '16 at 18:06
@MarkSpencer, a code generator producing machine code. – Andreas Rossberg Oct 17 '16 at 19:52
Isn't that a compiler? – Mark Spencer Oct 19 '16 at 20:01
Code generation is a part of a compiler's back-end, typically meaning machine code. What tools like Babel do is more accurately referred to as program generation. – Andreas Rossberg Oct 19 '16 at 21:10

Function documentation and syntax - ECMA262

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