docs: document generic comptime functions#175
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CalMacCQ
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July 9, 2026 21:50
CalMacCQ
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Jul 9, 2026
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| Note how the input to the `ladder` function is of type `array[qubit, k]` so this comptime function is generic over the number of qubits. | ||
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| Note that we cannot compile the `generic_ladder` function directly as the value of `k` is unknown at compile time. However we can call `generic_ladder` inside another function with a concrete `k` value. |
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Maybe it'd be instructive to call generic_ladder inside another function and compile it.
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Also I think it would be good to show the compiler error message when you try to compile it
CalMacCQ
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July 9, 2026 22:06
mark-koch
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Jul 13, 2026
| As we can see, the ``print`` statement is executed at compile-time. | ||
| We get 9 printed lines, highlighting that the ``for`` loop is compile-time evaluated as well. | ||
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| With Guppy v1.0 and above, we can use generic variables in the type signatures of generic functions. Let's generalize the `ladder` function defined above to apply a chain of `cx` gates to a qubit array of variable size. |
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Do we want to specifically call out v1 changes in regular docs sections?
| @guppy.comptime | ||
| def generic_ladder(qs: array[qubit, k]) -> None: | ||
| for q1, q2 in zip(qs[1:], qs[:-1]): | ||
| print("Applying CX") |
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| Note how the input to the `ladder` function is of type `array[qubit, k]` so this comptime function is generic over the number of qubits. | ||
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| Note that we cannot compile the `generic_ladder` function directly as the value of `k` is unknown at compile time. However we can call `generic_ladder` inside another function with a concrete `k` value. |
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Also I think it would be good to show the compiler error message when you try to compile it
Co-authored-by: Mark Koch <48097969+mark-koch@users.noreply.github.com>
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closes #94
This is really quite a powerful feature so I'm sure we can think of some cool algorithms to implement for the notebook examples.
As for the language guide, I've stuck with the basic cx ladder for now. We can remove the pre-V1 workaround where we define a comptime Guppy function inside a Python function and just have a generic type in the function signature.