Comments on: Visitors from Sheffield

Comments on: Visitors from Sheffield http://sneezy.cs.nott.ac.uk/fplunch/weblog/?p=16 abstracting the pain away Tue, 17 May 2011 07:05:56 +0100 hourly 1 http://wordpress.org/?v=3.0.3 By: Thorsten http://sneezy.cs.nott.ac.uk/fplunch/weblog/?p=16#comment-4 Thorsten Sun, 04 Dec 2005 12:25:30 +0000 http://sneezy.cs.nott.ac.uk/fplunch/weblog/?p=16#comment-4 I gave in to peer pressure too quickly, the way it was suggested to implement cobind for the stream comonad ([tex]C X = N \to X[/tex]) is incorrect, i.e. [tex] f^* g n = f g[/tex] doesn't work, because it doesn't satisfy the law [tex]\epsilon^* = 1[/tex]. The correct version is [tex]f^* g 0 = f g[/tex] and [tex] f^* g (1+ n) = f^* (g \circ 1+) n [/tex]. This is what I wanted to write... I gave in to peer pressure too quickly, the way it was suggested to implement cobind for the stream comonad ( $C X = N \to X$ ) is incorrect, i.e. f^* g n = f g

f^* g n = f g

doesn’t work, because it doesn’t satisfy the law $\epsilon^* = 1$ . The correct version is f^* g 0 = f g

f^* g 0 = f g

and $f^* g (1+ n) = f^* (g \circ 1+) n$ . This is what I wanted to write…

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