Add in-place variants for infer_pauli_measurements, to_bloch,...

[thierry-martinez]

Method Pattern.infer_pauli_measurements now operates in place by default, with an optional copy parameter. If copy=True, a modified copy is returned instead.

Added the following methods to Pattern. By default, they modify the pattern in place, with an optional copy parameter. If copy=True, a modified copy is returned instead.

• apply, an in-place variant of map,
• blochify, an in-place variant of to_bloch,
• substitute, an in-place variant of subs,
• replace_parameters, an in-place variant of xreplace.

This is a step toward the cleaner simulation API proposed in #493. It also makes the examples in the Graphix paper cleaner.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.59%. Comparing base (2d437e0) to head (86f69ce).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #568      +/-   ##
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+ Coverage   90.58%   90.59%   +0.01%     
==========================================
  Files          49       49              
  Lines        7481     7489       +8     
==========================================
+ Hits         6777     6785       +8     
  Misses        704      704              

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[matulni]

Thanks for the change, new functions are useful!

I'm not convinced by the naming of the parametric angle functions. The following are not very intuitive to me:

• subs and substitute have the same relationship as xreplace and replace_parameters.
• substitute and replace_parameters act in-place.
• subs replaces one parameter, and xreplace replaces multiple parameters in parallel. (I'm aware that this is a sympy convention and that it's independent of this PR, but I always found it difficult to remember. In addition, with the new methods we drift away from sympy's convention).

Here are two alternatives:

A)
substitute -> subs_in_place
replace_parameters -> xreplace_in_place

It solves 1) and 2), but it's more verbose and not true when calling subs_in_place(..., copy=True).

B)
subs -> substituted

substitute remains

xreplace -> substituted_multi

replace_parameters -> substitute_multi

I think this solves all three points but we don't follow sympy convention at all, and it requires a larger refactoring (we would need to update analogous methods in OpenGraph, etc.). If you think the -ed suffix may be easier to miss when reading the code, we could use with_substitution instead.

What do you think ?