What is Expressiveness in a Computer Language

[Joachim Durchholz]

Marshall schrieb:
> immutable = can't change
> vary-able = can change
> 
> Clearly a contradiction in terms.

Not in mathematics.
The understanding there is that a "variable" varies - not over time, but 
according to the whim of the usage. (E.g. if a function is displayed in 
a graph, the parameter varies along the X axis. If it's used within a 
term, the parameter varies depending on how it's used. Etc.)

Similarly for computer programs.
Of course, if values are immutable, the value associated with a 
parameter name cannot vary within the same invocation - but it can still 
vary from one invocation to the next.

Regards,
Jo