string methods

[anthonyberet]

I am an abject newbie, so mock away (actually no-one ever does that in 
this group..)

Anyway, I want to replace one character in a string, based in that 
character's position in the string.

For example if I wanted to replace the 4th character in 'foobar' (the 
b)with the contents of another string, newchar, what would be the 
easiest way?

I know this touches on immutability etc, but I can't find string methods 
to return the first 3 characters, and then the last 2 characters, which 
I could concatenate with newchar to make a new string.

I know the string methods are there, but can't find it in any docs, and 
just want to check the syntax, unless there is an easier way.

Thanks.