Re: Tiger's ESEQ

bsingharora@gmail.com wrote:
> I have been reading Andrew Appel's Modern Compiler Design in "C".
>
> I am afraid I do not understand the ESEQ completely.
>
> I have been looking at other literature like the Dragon book,
> Engineering a compiler, and many more. I have not found the usage of
> ESEQ kind of instructions anywhere in them. I understand the
> ide-effect part, but how do we know for sure that some instruction will
> have a side-effect. How do you define a side-effect?


It's not about the ultimate machine instruction, it's about the
operation being translated. Consider a C expression like:


        a[i++] = <something>


Consider just the i++ part. One simple way to translate that into
Appel's tree notation is something along these lines:


      ESEQ(temp <- i)
              (ESEQ(i <- i+1)
                        (temp)
              }


A comma expression as another natural application. It's really about
the structure of the tree, and representing it in a way that's actually
type-safe (and suitable for the ML version of the book), though if
you're writing in C you could yield to the temptation to use a SEQ instead.


    - ken

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