Modification of formulas without changing expression number

Questions
1

I made a
Original:

In[1]=a+b

In[2]=In[1]+3

…

If In[1] is modified to “a+b+2”, In[1] is changed to In[3].
So, I have to collect In[2] to In[3]+3.
All subsequent formulas have to be modified in the same way.
Is there any way to change only the content of the expression without changing the expression number?

2

Please check this note to know how to define your own function and change the parameter you need

3

Hi h r,

I’m not sure what you mean by “expression number”.

Are you trying to recursively define a function “In”, so that

In[i] depends on In[i-1] ?

Or are you trying to define a List “In”, so that

In[[i]] depends on In[[i-1]] ?

Note the syntax difference of single bracket “[” vs double bracket “[[”. The latter refers to Part, and is defined here: