[Python-ideas] Dart like multi line strings identation

[Steven D'Aprano]

On Sun, Apr 01, 2018 at 08:08:41AM -0400, Richard Damon wrote:

> One comment about the 'combitorial explosion' is that it sort of assumes
> that each individual combination case needs to be handled with distinct
> code.

No -- as I said in an earlier post, Terry and I (and Eric) are talking 
about the explosion in number of prefixes, not the complexity of the 
code.

You are right that many of the prefixes can be handled by the same code:

    rfd rfD rFd rFD rdf rdF rDf rDF
    Rfd RfD RFd RFD Rdf RdF RDf RDF
    frd frD fRd fRD fdr fdR fDr fDR
    Frd FrD FRd FRD Fdr FdR FDr FDR
    drf drF dRf dRF dfr dfR dFr dFR
    Drf DrF DRf DRF Dfr DfR DFr DFR
    # why did we support all these combinations? who uses them?

presumably will all handled by the same "raw dedent f-string" code. But 
the parser still has to handle all those cases, and so does the person 
reading the code.

And that *mental complexity* is (in my opinion) the biggest issue with 
adding a new d-prefix, and why I would rather make it a method.

Another big advantage of a method is that we can apply it to 
non-literals too.

The number of code paths increases too, but not anywhere as fast:

# existing
- regular ("cooked") triple-quoted string;
- raw string;
- f-string
- raw f-string

# proposed additions
- dedent string
- raw dedent string
- dedent f-string
- raw dedent f-string

so roughly doubling the number of cases. I doubt that will double the 
code complexity, but it will complicate it somewhat.

Apart from parsing, the actual complexity to the code will probably be 
similar whether it is a method or a prefix. After all, whichever we do, 
we still need built-in dedent code.


-- 
Steve