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Feature #1503

More flexible ring creation syntax (after use or ::=)

Added by John Abbott over 3 years ago. Updated over 3 years ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
enhancing/improving
Target version:
CoCoA-5.4.2
Start date:
08 Oct 2020
Due date:
% Done:

0%

Estimated time:
Spent time:
0.35 h

Description

This request comes from Florian Walsh.

The suggestion is permit the following syntax:

use QQ(a,b)[x,y];

which is intended to be shorthand for the cumbersome
QQab ::= Q[a,b];
k := NewFractionField(QQab);
use k[x,y];

Note that the cumbersome approach also uses two variables (and someone has to think of names for them).

Related issues

Related to CoCoA-5 - Feature #657: use command, ring syntax, RingOfNew2015-01-20

Related to CoCoA-5 - Feature #1003: New syntax for creating poly rings?In Progress2017-01-27

History

#1 Updated by John Abbott over 3 years ago

  • Related to Feature #657: use command, ring syntax, RingOf added

#2 Updated by John Abbott over 3 years ago

  • Related to Feature #1003: New syntax for creating poly rings? added

#3 Updated by John Abbott over 3 years ago

We discussed this over lunch today.

JAA thinks that this is not incompatible with #657.

Which term order should be used in the implicitly created ring QQ[a,b]?
JAA thinks the default order can be used; if the user really wants to specify some other order then the current "cumbersome" approach can be used.

If we want to implement this then we must change the parser/interpreter... ouch!
Relevant places in the source code are:
Parser.C: 356 inside parseUseStatement
Parser.C: 1397 inside parseFunBodyStatement
Parser.C: 1428 inside parseRingDefinition

Looks pretty scary to me!

#4 Updated by John Abbott over 3 years ago

How flexible/limited should a new syntax be?

Should it be possible to make arbitrarily long extensions? Such as

QQ(a)[x](b)[y][z]

A first attempt should probably allow just two levels (incl. QQ[x][y]???)

JAA is inclined to exclude quotient rings; so it would not be possible to write something like

(QQ[sqrt2]/ideal(sqrt2^2-2))[x]

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