Re: [Haskell-cafe] Prelude.head: empty list

Just thinking out loud here, but could one write their own Prelude which just imports hiding (head), adds a new definition of head, and reexports the lot. Then add this new Prelude higher in the search path perhaps? On Monday, 14 March 2016, Han Joosten wrote:

Thanks all! Plenty good options, fortunately I found my bug pretty fast by simple code inspection :))

2016-03-12 4:28 GMT+01:00 Chris Wong javascript:_e(%7B%7D,'cvml','lambda.fairy@gmail.com');>:

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On Sat, Mar 12, 2016 at 8:07 AM, Jonas Scholl javascript:_e(%7B%7D,'cvml','anselm.scholl@tu-harburg.de');> wrote:

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You mean like this?

default-extensions: CPP cpp-options:

-Dhead=(foldr(const)(error("head:\x20\x65mpty\x20list\x20in\x20"++__FILE__++":"++show(__LINE__))).(take$1))

That's pretty cool!

By the way: can the (take$1) be removed? foldr should be lazy enough already.

-- Chris Wong (https://lambda.xyz)

"I had not the vaguest idea what this meant and when I could not remember the words, my tutor threw the book at my head, which did not stimulate my intellect in any way." -- Bertrand Russell _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org javascript:_e(%7B%7D,'cvml','Haskell-Cafe@haskell.org'); http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe