2017-01-12 13:13 GMT+01:00 Stephan Houben :

Something like:

from __syntax__ import decimal_literal

which would feed the rest of the file through the "decimal_literal" transpiler. (and not influence anything in other files).

Not sure if you would want to support multiple transpilers per file.

Note that Racket has something similar with their initial "#lang ..." directive. That only allows a single "language". Possibly wisely so.

Stephan

2017-01-12 12:59 GMT+01:00 אלעזר :

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I think such proposals are special cases of a general theme: a compiler pragma, similar to "from __future__", to make Python support domain-specific syntax in the current file. Whether it's decimal literals or matrix/vector literals etc.

I think it will be nice to make some tool, external to Python, that will allow defining such "sibling languages" (transpiled into Python) easily and uniformly.

Elazar

בתאריך יום ה׳, 12 בינו' 2017, 13:21, מאת Paul Moore ‏

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On 12 January 2017 at 10:28, Victor Stinner wrote:

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George requested this feature on the bug tracker: http://bugs.python.org/issue29223

George was asked to start a discusson on this list. I posted the following comment before closing the issue:

You are not the first one to propose the idea.

OK, but without additional detail (for example, how would the proposed flag work, if the main module imports module A, then would float literals in A be decimal or binary? Both could be what the user wants) it's hard to comment. And as you say, most of this has been discussed before, so I'd like to see references back to the previous discussions in any proposal, with explanations of how the new proposal addresses the objections raised previously.

Paul

Most of the time one of my students talks to me about decimal vs

binary, they're thinking that a decimal literal (or converting the default non-integer literal to be decimal) is a panacea to the "0.1 + 0.2 != 0.3" problem. Perhaps the real solution is a written-up explanation of why binary floating point is actually a good thing, and not just a backward-compatibility requirement?

ChrisA

from __future__ import use_decimal_instead_of_float or any other import would be very good. The most important thing in my point of view is that I do not want to convert every variable every time to decimal. Accuracy is important for me (yes, 0.1 + 0.2 should equal to 0.3 , no more, no less ;-) ) And if it is mentioned, I would like to ask why binary floating point is "better". It is faster, I agree, but why "better"? Actually I create test automation (I am a senior QA eng), the fastest test case runs for about 1-2 minutes. I do not know the exact time difference between binary and decimal arithmetic, but I do not care with this. My test would run some microseconds faster. It does not matter at a minute range. In the tests I calculate with numbers with 4 decimal digits, and I need exact match. ;-) Actually I have a new colleague, they did image analysis, and the calculated much calculations, and they used a library (not python) that is accurate as well. Becasue accuracy was more important for them as well. BR George