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re: referential transparency Well, today I learned. "This set of functional expressions is referentially transparent" seems like yet another way of s...

Referential transparency actually means that the reference of an object doesn't matter. Only the value is important. That basically means that even items in different places in memory that have the same value are considered the same.

Actually, according to Willard Quine[1], "a mode of containment φ is referentially transparent if, whenever an occurrence of a singular term t is purely referential in a term or sentence ψ(t), it is purely referential also in the containing term or sentence φ(ψ(t))," as in the following example:

(12) Ralph believes that the man in the brown hat is a spy.
(13) Ralph does not believe that the man seen at the beach is a spy.
The main in the blue hat = the man seen at the beach = Bernie Sanders
t = ‘the man in the blue hat’
ψ(t) = ‘the man in the blue hat is a spy’
ϕ(ψ(t)) = ‘Ralph believes that the man in the blue hat is a spy’.

I need to get more practice drawing lil tridents on whiteboards.

[1]Although ultimately, like many obtuse concepts in CS, we can safely blame Whitehead and Bertram.

Hmm, well I was talking about referential transparency as it relates to functional programming, as opposed to logic, I guess. I hadn't seen that definition before, it's pretty interesting.

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