feat: add lambda expression support#710
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benbellick
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benbellick
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Only just started looking at this but flushing a few comments just to get the ball rolling. On the whole this is looking good though, nice work!
| List<Type> paramTypes = parameters().fields(); | ||
| Type returnType = body().getType(); | ||
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| return Type.withNullability(false).func(paramTypes, returnType); |
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Is setting nullability false correct here? I am pretty sure func can be nullable, e.g. func?<i32 -> i32>.
Also, probably will be good to make a test captures this then.
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I followed the substrait-go implementation: the GetType function for lambda returns Nullability: types.NullabilityRequired
func (l *Lambda) GetType() types.Type {
return &types.FuncType{
Nullability: types.NullabilityRequired,
ParameterTypes: l.Parameters.Types,
ReturnType: l.Body.GetType(),
}
}
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hmm I am thinking about this right now but that may have been wrong in substrait-go 🤔
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I think this is a spec error. I raised an issue in upstream here.
Mind leaving a comment there referencing this issue as a TODO so we remember to fix it once it gets resolved?
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| @Value.Immutable |
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This is okay if you feel confident in your LambdaInvocation work, but considering the size of this PR, it will make it easier both on you and the reviewer to separate out the Lambda work and LambdaInvocation work into two separate PRs.
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I'll handle LambdaInvocation in a separate pr
| private final Type.Struct rootType; | ||
| private final ProtoTypeConverter protoTypeConverter; | ||
| private final ProtoRelConverter protoRelConverter; | ||
| private final List<Type.Struct> lambdaParameterStack = new ArrayList<>(); |
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I need to access lambdaIndex = lambdaParameterStack.size() - 1 - stepsOut here: lambdaParameters = lambdaParameterStack.get(lambdaIndex); when building the Lambda parametre ref that's why I didn't use a stack
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That's fair. Java's stack does extend Vector though so you still get the get method. I'm not so particular on this one.
The only thing I will say is I do think that the whole stack parameter stuff can be confusing for people without a little bit of PL experience, which is why I pushed @Slimsammylim to encapsulate some of that logic and put it in docstring comments. I could see a case for encapsulating this logic in a local private class, though it probably makes more sense to do this only if this logic comes up again.
I expected to see something like this logic elsewhere, as you need to do it to do validation when building lambdas. Though I didn't find anything like this. Does the builder for lambdas in this PR actually validate that the lambda is semantically correct?
| .setStruct(protoLambda.getParameters()) | ||
| .build()); | ||
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| lambdaParameterStack.add(parameters); |
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then we can use the standard stack push here
| try { | ||
| body = from(protoLambda.getBody()); | ||
| } finally { | ||
| lambdaParameterStack.remove(lambdaParameterStack.size() - 1); |
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and the standard stack pop here
3 participants
This PR is to add support for the Lambda Expression
Summary
Test plan
closes #687