On Mon, Apr 28, 2014 at 11:30 AM, John M. Dlugosz
On 4/27/2014 11:24 PM, Magnus Therning wrote:
It most likely sees it as the binary minus rather than the unary minus.
That's what I thought.
Couldn't match expected type `Picture' with actual type `Float -> Picture -> Picture' In the expression: translate - 50 0 $ color green (Circle 50) In the first argument of `Pictures', namely `[Circle 100, translate - 50 0 $ color green (Circle 50), scale 200 200 $ color red $ (Pictures $ take 20 chain1), testcirc]' In the expression: Pictures [Circle 100, translate - 50 0 $ color green (Circle 50), scale 200 200 $ color red $ (Pictures $ take 20 chain1), testcirc]
But what is the error message telling me? Given that infix is done after adjacency application, it should parse as: ((translate - (50 0) ) $ (color (green (Circle 50))))
Left of the $, that is the parse tree
subtract+ | + translate | + apply+ | + 50 | + 0
I think it would complain that 50 isn't a function, or the first argument of subtract is not a Num but a function translate :: Float -> Float -> Picture -> Picture, or that the argument of translate isn't a Float but something it can't make sense of. Why is it looking for a Picture? Where is it getting Float->Picture->Picture (seems to be a curried translate? But the next token is not something it would like so how can it find a first argument?)
Understanding the compiler's errors is a skill I want to learn, as well as shake out my understanding of what's really going on.
It's not easy to answer that without knowing the types of the involved values/functions. You can always play around a bit in ghci with the ':type' command to see if you can work it out for yourself :) It can be confusing though, functions are values too, and precedence rules come into play too. /M -- Magnus Therning OpenPGP: 0xAB4DFBA4 email: magnus@therning.org jabber: magnus@therning.org twitter: magthe http://therning.org/magnus