[Edu-sig] Re: easy for beginners, even children

[Michael McLay]

On Thursday 15 April 2004 2:26 am, Terry Hancock wrote:
> On Wednesday 14 April 2004 05:54 pm, Daniel Ajoy wrote:
> > > But why would they say "set 2 equal to 3" if they want
>
> to
>
> > > know "is 2 equal to 3"?
> >
> > Because 2 = 3 is what they would write on paper.
> >
> > But I agree that it does not take much brilliance to
> > understand that = and == are different things, and when
> > to use each one.
>
> Actually there's a very important lesson there. One thing
> that takes some appreciation is that programming (well,
> procedural programming) is *prescriptive*, not
> *descriptive*, which makes it different from, say algebra.
>
> I mean:
>
> x = x + 1
>
> is an extremely common thing to do in programming (so common
> we have a shortcut
>
> x += 1
>
> ).
>
> But that's obviously a false statement in algebra.
> Therefore it's really important to point out that we are
> doing two fundamentally different things when we are
> *assigning* a value and when we are *testing* a value.

If might be helpful to explain that algebra is also an arbitrary syntax. It 
just happens to have several hundred years of refinement and general 
acceptance by the mathematics community. (The design of computer languages 
are constrained by historical and pragmatic keyboard and display device 
limitations. These limitations were part of the motivation for the special 
encoding of expressions in programming languages.) It can also be pointed out 
that just as there are an infinite number of possible algebra languages 
possible, there is also an infinite number of possible computer languages 
possible. Python, like all computer languages, defines a concrete syntax that 
is agreed upon as as the rules for expressing how a program should operate. 

Python could have just as easily have spelled '==' with '.eq.'. That is the 
spelling for an equality symbol in other languages. If you wanted to make it 
more like COBOL the spelling of this operation might have been spelled 
'.IS_EQUAL_TO.', but that would be very painful to keyboard compared to '=='. 
The decision on the spelling of symbols is an aesthetic choice. This 
arbitrary assignment of a symbol is no different than the arbitrary spelling 
of the word 'esthetic'. Just as the word 'centre' is the same word as 
'center'. The "correct" spelling is a customary choice of different 
countries. The spelling choices for Python were selected by the BDFL. One 
innovation of Python is there are fewer ways to express the same concept and 
there is generally one way that is considered more correct than any other in 
most circumstances. This make it much easier to read other peoples writting 
in Python. It's his language. If a student complains about the BDFL's choices 
for the Python syntax rules then I suggest a few hours of instruction on the 
rules of Perl to enlighten them on the alternative:-)

> Even if the syntax let us confuse these two operations (as
> it could -- Python doesn't really need two different
> symbols for these operations since the assignment is
> illegal in tests), it's still a good thing to learn.

Reusing the same spelling for both assignment and equality would present 
problems in expressions.
>>> a = 1
>>> b = 4
>>> a = b == 3
>>> a
False
>>> a = b = 3
>>> a
3
>>> b
3
>>>

> Algorithms are fundamentally different from equations, and
> this is a good place for the student to learn something. A
> potential "Aha!" moment, in fact.

As far as case sensitivity is concerned, there are times when the semantics of 
a sentence can be derived from the case used in spelling a word. For 
instance.

The president of GM told the President, "What's good for GM is good for 
America". The President had no comment.

It is very clear from this sentence that the President of the United States 
was the person who had no comment. Sometimes capitalization does matter in 
English. The first word in a sentence is capitalized. Proper nouns are 
capitalized. Python has defined a very restrictive rule on how names are 
treated in the language. This is another example of a simplification that 
make it easier to read software written by someone else. It eliminates the 
creation of arbitrary styles for writing names in programs. When a student 
asks why case matters, simply ask why it shouldn't matter. If they think it 
would be easier to use Python if they can be inconsistent in their use of 
case, then they have the answer. Python helps teach that consistency matters.

I think the point to learn from these examples is that learning to program can 
be a good tool for teaching the importance of accuracy in the expression of 
ideas. If you make the mistake in an English paragraph the human parsing the 
sentence may make an arbitrary assumption of the meaning, or they may point 
out the ambiguity. The computer program will not make arbitrary decisions. 

I think it is great that programming is an opportunity to improve a student's 
writing skills. Decades ago, high school students heading for college were 
taught Latin. Teaching this dead language helped teach students more about 
how languages are structured. To a small degree computer programming is an 
opportunity to replace this lost art.