Add QkParam to the C API (#14837)

* Add C-API for ParameterExpression

* add test cases for Parameter C-API

* rename qk_paramter_ to qk_param_, fix array format of bind/subs functions

* fix test for param

* use existing QkParam to save results of operations

* fix test_param.c

* fix test_param.c

* fix for lint, add releasenote

* Update crates/cext/src/param.rs

Co-authored-by: Julien Gacon <[email protected]>

* Update crates/cext/src/param.rs

Co-authored-by: Julien Gacon <[email protected]>

* Update crates/cext/src/param.rs

Co-authored-by: Julien Gacon <[email protected]>

* Update crates/cext/src/param.rs

Co-authored-by: Julien Gacon <[email protected]>

* Update crates/cext/src/param.rs

Co-authored-by: Julien Gacon <[email protected]>

* Update crates/cext/src/param.rs

Co-authored-by: Julien Gacon <[email protected]>

* Update crates/cext/src/param.rs

Co-authored-by: Julien Gacon <[email protected]>

* add qk_param_zero(), rename qk_param_new to qk_param_new_symbol

* remove unsafe from qk_param_zero

* rename ``qk_param_str`` for consistency

compare to ``qk_obs_str``

* Cleanup tests

- use goto for shorter code
- handle QkExitCode from arithmetic functions
- add docstrings

* Doc chores

- proper code highlighting
- fix C code sections
- fix safety sections
- update exit code docs

* Docs & small improvements for bind/subs

* More tests

* Update reno

* Jake's review comments - light edition

the others are for follow ups :)

* drop bind/subs for now

there are open discussions on what the right interface to reduce the allocations in practice. Let's unblock parameters while we have this discussion

* one more go at safer print

* update reno

* fix test artifact

* fix rust edition 2024

* don't use VLA (thanks MSVC)

* rm string prints

* rm ctype

---------

Co-authored-by: Julien Gacon <[email protected]>
Co-authored-by: Julien Gacon <[email protected]>

Author: doichanj

crates/cext/cbindgen.toml

@@ -85,3 +85,4 @@ prefix_with_name = true
 "TranspileLayout" = "QkTranspileLayout"
 "TranspileResult" = "QkTranspileResult"
 "TranspileOptions" = "QkTranspileOptions"
+"Param" = "QkParam"

crates/cext/src/exit_codes.rs

@@ -10,6 +10,7 @@
 // copyright notice, and modified files need to carry a notice indicating
 // that they have been altered from the originals.
 
+use qiskit_circuit::parameter::parameter_expression::ParameterError;
 use qiskit_quantum_info::sparse_observable::ArithmeticError;
 use qiskit_transpiler::target::TargetError;
 use thiserror::Error;
@@ -96,3 +97,9 @@ impl From<TargetError> for ExitCode {
         }
     }
 }
+
+impl From<ParameterError> for ExitCode {
+    fn from(_value: ParameterError) -> Self {
+        ExitCode::ArithmeticError
+    }
+}

crates/cext/src/lib.rs

@@ -14,5 +14,6 @@ mod pointers;
 
 pub mod circuit;
 pub mod exit_codes;
+pub mod param;
 pub mod sparse_observable;
 pub mod transpiler;