how can I improve this

Hello,

I have solved the hamming challenge of exercism where I have to find in
how many places two strings are different.

my solution is :

distanceStrand1: aString strand2: aString2
     aString size == aString2 size
         ifFalse: [ DomainError signal: (self messageFor: aString
strand2: aString2) ].
     ^ (1 to: aString size)
         sumNumbers: [ :index |
             (aString at: index) == (aString2 at: index)
                 ifTrue: [ 0 ]
                 ifFalse: [ 1 ] ]


messageFor: aString strand2: aString2
     aString notEmpty & aString2 notEmpty
         ifTrue: [ ^ 'left and right strands must be of equal length' ].
     aString ifEmpty: [ ^ 'left strand must not be empty' ].
     ^ 'right strand must not be empty'


Can this be improved?

Roelof

Hi Roelof,

Maybe something like this:

String>>hammingDistanceTo: aString
	" Answer the amount of substitutions between the receiver and aString. Both must be of equal length "

	^ (1 to: self size) count: [ : i | (self at: i) ~= (aString at: i) ]

El lun., 14 sept. 2020 a las 16:15, Roelof Wobben via Pharo-users (<[hidden email]>) escribió:

Hello,

I have solved the hamming challenge of exercism where I have to find in
how many places two strings are different.

my solution is :

distanceStrand1: aString strand2: aString2
     aString size == aString2 size
         ifFalse: [ DomainError signal: (self messageFor: aString
strand2: aString2) ].
     ^ (1 to: aString size)
         sumNumbers: [ :index |
             (aString at: index) == (aString2 at: index)
                 ifTrue: [ 0 ]
                 ifFalse: [ 1 ] ]


messageFor: aString strand2: aString2
     aString notEmpty & aString2 notEmpty
         ifTrue: [ ^ 'left and right strands must be of equal length' ].
     aString ifEmpty: [ ^ 'left strand must not be empty' ].
     ^ 'right strand must not be empty'


Can this be improved?

Roelof

^ (1 to: self size) count: [ : i | (self at: i) ~= (aString at: i) ]

With that code I get a few problems but this is working

distanceStrand1: aString strand2: aString2
    aString size == aString2 size
        ifFalse: [ DomainError signal: (self messageFor: aString strand2: aString2) ].
    ^ (1 to: aString size)
        count: [ :i | (aString2 at: i) ~= (aString at: i) ]

Roelof

SequenceableCollection has with:do:.

Add

    with: other count: testBlock

        |r|

        r := 0.

        self with: other do: [:x :y |

            (testBlock value: x value: y) ifTrue: [r := r + 1]].

        ^r

I have this in my library anyway.  Now

distanceStrand1: a strand2: b

    ^a with: b count: [:x :y | x ~= y]

#with:do: already checks that the sequences have the same size;

it's too confusing if the error reported in this case is different

from the error for #with:do:.

On Tue, 15 Sep 2020 at 16:59, Roelof Wobben via Pharo-users <[hidden email]> wrote:

Op 14-9-2020 om 22:19 schreef Hernán Morales Durand:

^ (1 to: self size) count: [ : i | (self at: i) ~= (aString at: i) ]

With that code I get a few problems but this is working

distanceStrand1: aString strand2: aString2
    aString size == aString2 size
        ifFalse: [ DomainError signal: (self messageFor: aString strand2: aString2) ].
    ^ (1 to: aString size)
        count: [ :i | (aString2 at: i) ~= (aString at: i) ]

Roelof

with: other count: testBlock

        |r|

        r := 0.

        self with: other do: [:x :y |

            (testBlock value: x value: y) ifTrue: [r := r + 1]].

        ^r

nope, all the test on a error are yellow and this two test on  counting are yellow.

test03_SingleLetterDifferentStrands
    | result |
    result := hammingCalculator distanceStrand1: 'G' strand2: 'T'.
    self assert: result equals:

gives 0 instead of 9.

and this one fails :

test05_LongDifferentStrands
    | result |
    result := hammingCalculator
        distanceStrand1: 'GGACGGATTCTG'
        strand2: 'AGGACGGATTCT'.
    self assert: result equals: 9

also this one gives 0 instead of 9.