In the first method you aren't doing an assignment, are sending the message = to the temp isValid, if you change the method to:
decimalFromBinary: aString
�������� | result isValid |
�������� isValid := self isValidBinary: aString.
�������� isValid
�������� ������ ifTrue: [ result := 0.
�������� ������ ������ aString reverse
�������� ������ ������ ������ withIndexDo:
�������� ������ ������ ������ ������ [ :digit :index | result := result + (digit
digitValue * (2 raisedTo: index - 1)) ].
�������� ������ ������ ^ result ]
�������� ������ ifFalse: [ ^ nil ]
it should work.

In the second one you're comparing characters with numbers, this will always return false because the number 0 is not the same as the character 0.
Use
isValidBinary: aString
�������� ^ aString allSatisfy: [ :c | c = $0 or: [ c = $1 ] ]
or something like

isValidBinary: aString
�������� ^ aString allSatisfy: [ :c | '01' includes: c ]

On Sun, Apr 26, 2020 at 2:52 PM Roelof Wobben via Pharo-users <pharo-users@lists.pharo.org> wrote:
Hello,

I have to make some code that convert a binary to a decimal and im not
allowed to use the convert methods that Pharo has.

So I have written this :


decimalFromBinary: aString
�������� | result isValid |
�������� isValid = self isValidBinary: aString.
�������� isValid
�������� ������ ifTrue: [ result := 0.
�������� ������ ������ aString reverse
�������� ������ ������ ������ withIndexDo:
�������� ������ ������ ������ ������ [ :digit :index | result := result + (digit
digitValue * (2 raisedTo: index - 1)) ].
�������� ������ ������ ^ result ]
�������� ������ ifFalse: [ ^ nil ]

isValidBinary: aString
�������� ^ aString allSatisfy: [ :c | c = 0 or: [ c = 1 ] ]


but on the first method I see a message that the temp variables are read
before written.
and the second one I see a message that I use a or instead of searching
literals.

Where did�� I think wrong here ?

Roelof