Implement __index__ for PARI Gen

[defeo]

Pari integers cannot be used to index lists:

sage: [1,2][pari(1)]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-f2823fec0752> in <module>()
----> 1 [Integer(1),Integer(2)][pari(Integer(1))]

TypeError: list indices must be integers, not sage.libs.cypari2.gen.Gen

With this ticket

sage: [1,2][pari(1)]
2

Incidentally, this also fixes pow

sage: 1^pari(1)
1

CC: @jdemeyer @videlec

Component: interfaces

Keywords: PARI, rd3

Author: Jeroen Demeyer

Branch/Commit: 50593d6

Reviewer: Luca De Feo

Issue created by migration from https://trac.sagemath.org/ticket/22319

[jdemeyer]

Author: Jeroen Demeyer

[jdemeyer]

Branch: u/jdemeyer/implement___index___for_pari_gen

[jdemeyer]

New commits:

0348e00

Implement `__index__` for PARI Gen

[jdemeyer]

Commit: 0348e00

[defeo]

comment:5

This only solves part of the issue:

sage: 2^1.5
2.82842712474619
sage: 2^pari(1.5)
---------------------------------------------------------------------------
PariError                                 Traceback (most recent call last)
...
PariError: incorrect type in coercion to integer (t_REAL)

[jdemeyer]

comment:6

Feel free to create a new ticket for other related issues.

[jdemeyer]

comment:7

Although the exception type could be improved...

[sagetrac-git]

Changed commit from 0348e00 to 50593d6

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

50593d6

Minor fixes to __index__

[defeo]

comment:10

I call this "ticket hijacking" :p

[defeo]

Reviewer: Luca De Feo

[defeo]

Changed keywords from PARI to PARI, rd3

[vbraun]

Changed branch from u/jdemeyer/implement___index___for_pari_gen to 50593d6