44 lines
1.9 KiB
Markdown
44 lines
1.9 KiB
Markdown
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---
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layout: site
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author: Torsten
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---
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As noted in previous posts, differentiating between compile- and run-time is one of the more
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difficult things in doing the vm. That is because the computing that needs to happen is so similar,
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in other words almost all of the vm - level is available at run-time too.
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But off course we try to do as much as posible at compile-time.
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One hears or reads that exactly this is a topic causing (also) other vms problems.
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Specifically how one assures that what is compiled at compile-time and and run-time are
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identical or at least compatible.
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The obvious answer seems to me to **use the same code**.In a way that "just" moves the question
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around a bit, becuase then one would have to know how to do that. I'll go into that below,
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but find that the concept is worth exploring first.
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Let's take a simple example of accessing an instance variable. This is off course available at
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run-time through the function *instance_variable_get* , which could go something like:
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def instance_variable_get name
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index = @layout.index name
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return nil unless index
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at_index(index)
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end
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Let's assume the *builtin* at_index function and take the layout to be an array like structure.
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As noted in previous posts, when this is compiled we get a Method with Blocks, and exactly one
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Block will initiate the return. The previous post detailed how at that time the return value will
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be in the ReturnSlot.
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So then we get to the idea of how: We "just" need to take the blocks from the method and paste
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them where the instance variable is accessed. Following code will pick the value from the ReturnSlot
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as it would any other value and continue.
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The only glitch in this plan is that the code will assume a new message and frame. But if we just
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paste it it will use message/frame/self from the enclosing method. So that is where the work is:
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translating slots from the inner, inlined fuction to the outer one. Possibly creating new frame
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entries.
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tbc
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