�� (s occurrencesOf: $() - (s occurrencesOf: $)); cr.

Make no mistake: you *cannot* tell the difference

between $( and $) using class-based dispatch because

they belong to the same class.�� There has to be an

"if" somewhere, the question is not whether but where.

In this case, counting the number of occurrences of an

object in a collection is has been a standard Collection

method for nearly 40 years; it's one of the basic

operations you need to learn.

The "higher level" approach can be less efficient that

the "CS101" approach, but in a case like this we really

do not care.�� We want the code to be *clear*.

What about the second part of the problem?

Not having submitted any answers, I can't actually

see the second part on the AOC site, but luckily you

have included it in your program.

We want to

�� [find the first place] where

�� [the cumulative sum] of (c=$()

�� [minus]

�� [the cumulative sum] of (c=$))

�� equals -1.

The "CS101" approach is

�� n := i := 0.

�� while n >= 0 and i < size(s) do

�� i��+:= 1

�� if s[i] = $( then n := n��+ 1

�� if s[i] = $) then n := n - 1

�� report n

The "higher level" approach looks something like

�� n :=
                          (s cumCount: [:each | each = $(]) -

�� �� ��
                          ��(s cumCount: [:each | each = $)])

�� �� ��
                          ��indexOf: -1.

--
                          although it gives 0 instead of s size��+ 1 when

-1 is
                          never reached.

Here
                          #indexOf: is standard, #- is defined on
                          sequences

in
                          Squeak and Pharo, but #cumCount: does not

exist.��
                          So we need something like

�� cumCount: aBlock��

�� |c a|��

�� a := Array new: self size.

�� c := 0.

�� self withIndexDo: [:each :i |

�� (aBlock value: each) ifTrue: [c := c + 1].

�� a at: i put: c].

�� ^a

This
                            is *not* coupled to the particular use we
                            have

in
                            mind for it; it is in no way tied to
                            characters

or
                            strings.�� It's quite general.

Note:
                            we do not need any new classes, except maybe

a
                            place to put one problem-specific method.

While
                            this answer, with no loop and no if in the

problem-specific
                            code, is quite pretty, it has a

problem.��
                            Suppose the string to have M characters

and
                            the desired step to be number K.�� The CS101

approach
                            takes O(K) time and no allocations, but

the
                            higher level approach takes O(M) time and

allocates
                            three M-element Arrays.�� (In a non-strict

functional
                            language like Haskell, the higher level

version
                            *also* takes O(K) time, and with a good

enough
                            "deforesting" compiler should allocate no

data
                            structures.)

For
                            a problem like this, I really don't care
                            about

the
                            efficiency aspect.�� If I *do* care about
                            that,

then
                            starting from a higher level version gives
                            me

something
                            to test a lower level version against.

To
                            get an efficient answer to the second part,

we
                            still don't need a new semantic class, just

some
                            place to put the code.

Day1

��
                            class methods:

�� ��
                            indexOfFirstBasementTime: steps

�� ��
                            �� |floor|

�� ��
                            �� floor := 0.

�� ��
                            �� steps keysAndValuesDo: [:i :each |

�� ��
                            �� �� each = $( ifTrue: [floor := floor��+ 1].

�� ��
                            �� �� each = $) ifTrue: [floor := floor - 1].

�� ��
                            �� �� floor = -1 ifTrue: [^i]].

�� ��
                            �� ^0 "same convention as #indexOf:"

Does
                            this contain "if"?�� Why yes, it does.

Is
                            there any problem with that?�� Why no, there
                            isn't.

You
                            need to treat members of the same class
                            (left

parenthesis,
                            right parenthesis, others) differently.

You
                            need to treat members of the same class
                            (minus

one,
                            all other integers) differently.

Would
                            there be any gain in clarity or
                            maintainability

if
                            these ifs were somehow eliminated?��
                            Certainly NOT.

Quite
                            the reverse, in fact.

input2
                              withIndexDo: [ :element :index | |action|��
	action:=
                              SantaAction getActionFor: element. floor
                              := action�� doMovementFor: floor .
	self
                              hasReachedBasement��
	ifTrue:
                              [^ index]].
�� �� ^ '-2'.


                            
There is only one
                              word for this: obfuscated.
I was initially
                              puzzled by your returning -2
instead of the
                              conventional 0 if the basement
is not reached,
                              and then *deeply confused* by
the fact that you
                              are returning a *string* in
this case.


                            
Looking at your
                              code, I was further confused
by variables
                              called 'aSymbol' whose value is
always and only a
                              Character, never a Symbol.
And if I am wrong
                              that

                              
                                
                                    IllegalMoveSanta class>> canHandleInput:

                                  

                              
                            
in Smalltalk is
                              to return 0 when something is

�� ��
                            ����

approach

We want to find the first place where something

becomes true.�� There are again at least to approaches.��