Dear all, I have tried to adapt ListEdit.ur in the tutorial to a small SVG
application that adds circles to the screen as you double click (the code is at
the end). The SVG.urs is found at
https://github.com/karsar/urweb-examples/blob/master/SVGTest/SVG.urs
I get a problem at row 57 "<dyn signal={circleDraw p}/>" and also at line 22
"show' (pl : plist) : signal xsvg =" where the compiler gets stuck on "Error
in final record unification
Can't unify record constructors". My hypothesis is that there is some problem
between html and SVG.
An excerpt of the error messages sis:
/home/a/SVGTest5/SVGTest.ur:57:3: (to 58:8) Error in final record unification
Can't unify record constructors
Have: <UNIF:U571::{Unit}> ++ [Dyn = ()]
Need: [Svg = ()]
/home/a/SVGTest5/SVGTest.ur:57:3: (to 58:8) Stuck unifying these records after
canceling matching pieces:
Have: ([Dyn = ()]) ++ <UNIF:U571::{Unit}>
Need: [Svg = ()]
/home/a/SVGTest5/SVGTest.ur:57:10: (to 57:30) Error in final record unification
Can't unify record constructors
Have:
[Signal =
signal (xml (([Dyn = ()]) ++ <UNIF:U571::{Unit}>) ([]) ([]))]
Need:
<UNIF:U550::{Type}> ++ [Signal = signal (xml ([Svg = ()]) ([]) ([]))]
Field: #Signal
Value 1:
signal (xml (([Dyn = ()]) ++ <UNIF:U571::{Unit}>) ([]) ([]))
Value 2: signal (xml ([Svg = ()]) ([]) ([]))
Can't unify record constructors
Have: <UNIF:U571::{Unit}> ++ [Dyn = ()]
Need: [Svg = ()]
/home/a/SVGTest5/SVGTest.ur:22:10: (to 22:22) Error in final record unification
Can't unify record constructors
Have: <UNIF:U168::{Unit}> ++ [Dyn = ()]
Need: [Svg = ()]
/home/a/SVGTest5/SVGTest.ur:22:10: (to 22:22) Stuck unifying these records
after canceling matching pieces:
Have: ([Dyn = ()]) ++ <UNIF:U168::{Unit}>
Need: [Svg = ()]
/home/a/SVGTest5/SVGTest.ur:26:9: (to 26:35) Error in final record unification
Can't unify record constructors
Have:
[Signal =
signal (xml (([Dyn = ()]) ++ <UNIF:U168::{Unit}>) ([]) ([]))]
Need:
<UNIF:U147::{Type}> ++ [Signal = signal (xml ([Svg = ()]) ([]) ([]))]
Field: #Signal
Value 1:
signal (xml (([Dyn = ()]) ++ <UNIF:U168::{Unit}>) ([]) ([]))
Value 2: signal (xml ([Svg = ()]) ([]) ([]))
Can't unify record constructors
Have: <UNIF:U168::{Unit}> ++ [Dyn = ()]
Need: [Svg = ()]
===== CODE =====
open SVG
datatype plist = Nil | Cons of {Point : source (int*int),
Tail: source plist}
(*con intPair = int*int*)
fun fst (x: int*int) = x.1
fun snd (x: int*int) = x.2
fun circleDraw x : signal xsvg =
x' <- signal x;
return
<xml>
<circle cx={show ((fst x')-60)} cy={show ((snd
x')-100)} r="10" stroke="red" fill="blue"/>
</xml>
fun show (pl: source plist) : signal xsvg =
pl <- signal pl;
show' pl
and show' (pl : plist) : signal xsvg =
case pl of
Nil => return <xml/>
| Cons {Point = p, Tail = t } => return <xml>
<dyn signal={circleDraw p}/>
</xml>
fun proc () =
l <- source Nil;
tailP <- source l;
point <- source (0,0);
let
fun add () =
p <- get point;
p' <- source p;
tail <- get tailP;
tail' <- source Nil;
let
val cons = Cons
{Point = p', Tail = tail'}
in
set tail cons;
set tailP tail';
l' <- get l;
case l' of
Nil => set l cons
| _ => return ()
end
in
return
<xml>
<body ondblclick={fn ev => set point
(ev.ScreenX,ev.ScreenY); add()}>
<div
style="width:800; heigth:800">
<svg width="800"
height="600">
<dyn signal={show
l}/>
</svg>
</div>
</body>
</xml>
end
fun main() =
xml <- proc ();
return
<xml>
<head>
Banzai
</head>
{xml}
</xml>
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