349 reputation
313
bio website
location
age
visits member for 2 years, 4 months
seen Dec 1 at 19:42

I am.


May
1
awarded  Enthusiast
Apr
17
comment In Scheme, what is formally a program's state?
Thanks for the reference, i will look at that book. About the substitution model, it is claimed in SICP that it is not appropriate once you allow assignment.
Apr
17
revised Is Liskov Substitution Principle incompatible with Introspection or Duck Typing?
add <!-- language: lang-rb --> to highlight Ruby syntax
Apr
17
comment In Scheme, what is formally a program's state?
I am now at lecture 5 out of 10 on SICP, and it looks to me that the environment (in the form of a pointer in a rooted tree of frames, each frame consisting of variable bindings), should be a part of the state.
Apr
17
comment In Scheme, what is formally a program's state?
I think when i was asking for a simplest definition, i meant the one where transitions from state to state would be the easiest to define. Otherwise it can be said that a program has only 2 states: the program itself and its result, and everything happens during the transition from the first to the second.
Apr
14
comment In Scheme, what is formally a program's state?
There is however something awkward with this semantics/state: its use of define seems far from optimal. To make a "small step" of replacing an identifier with its definition, the whole program must be searched for a matching define or set!. This semantics looks to me a bit impractical even from theoretical view point. The rules for searching for a matching define are complicated (for example, it should not occur in a quoted expression).
Apr
3
accepted In Scheme, what is formally a program's state?
Apr
3
comment In Scheme, what is formally a program's state?
John, your definition of state agrees with this lecture of a course on Structure and Interpretation of Computer Programs.
Mar
29
comment In Scheme, what is formally a program's state?
Thanks for the link, Paul. I hoped there was an easier description of a state that "machine memory". By the way, it is not a complete definition, because you would need to also define what is stored in the memory and how. I will try to look through the article.
Mar
29
comment In Scheme, what is formally a program's state?
I have though of this, but could not convince myself that there is nothing more in a state. For example, if there is some external input-output. Could you give me some reference to more information on small-step semantics for Scheme, please? It is hard for me for now to translate operational semantics to such "program transformation" semantics, for example i do not see what would be a small step to reduce something like (quote x), or why this form is "irreducible".
Mar
28
comment In Scheme, what is formally a program's state?
I think i would be satisfied with any single answer out of infinitely many, preferably the shortest one, for any single "semantics". (I guess that without a semantics a Scheme program is just a sequence of Unicode symbols anyway.) If a Scheme program is not to be evaluated but to be "reduced", i would be interested to hear about it too, but from what i have read so far, it looks like after all a Scheme program describes a "computation" in some sense. As far as i know, a computation must be a sequence of states.
Mar
28
comment In Scheme, what is formally a program's state?
Thanks for the information and references, but i am looking for a one- or two-line definition if possible.
Mar
28
asked In Scheme, what is formally a program's state?
Mar
25
awarded  Notable Question
Feb
27
comment Is there an idiom for a loop that executes some block of instructions between iterations? (In Ruby in particular)
It seems that this is an inherent fault in all loop constructs that i know: for some reason the default exit point is always put just before the entry point, but i see no reason whatsoever for this to be a common scenario. In my opinion, most loops are "loops-and-a-half".
Feb
27
accepted Is there an idiom for a loop that executes some block of instructions between iterations? (In Ruby in particular)
Feb
27
comment Is there an idiom for a loop that executes some block of instructions between iterations? (In Ruby in particular)
Hm, it does not look like the output of ERB will be what i want. In fact, i would want to output blocks of HTML in a loop, joining them with other blocks, on so that the ERB or Haml template was easily readable.
Feb
26
comment Is there an idiom for a loop that executes some block of instructions between iterations? (In Ruby in particular)
Thanks for the Haskel example anyway.
Feb
26
comment Is there an idiom for a loop that executes some block of instructions between iterations? (In Ruby in particular)
Unfortunately, this solution will not look very clear inside a template language like ERB or Haml, at least i do not see how to make it clear.
Feb
26
comment Is there an idiom for a loop that executes some block of instructions between iterations? (In Ruby in particular)
Can you be more specific, please?