I'm trying to use the value of a textarea with js_of_ocaml. Here is my source code :
let matrix () =
let text1 = get_textarea "input_1" in
let btn1 = get_elem "btn_1" in
text1##placeholder <- Js.string "Write your matrix !";
btn1##textContent <- Js.some (Js.string "Calculate");
btn1##onclick <- Dom_html.handler (if Matrix.is_matrix (Js.to_string text1##value)
then (let matrix = Matrix.get_matrix (Js.to_string text1##value) in
fun ev -> (set_matrix_caracteristics (Matrix.nb_lines matrix) (Matrix.nb_columns matrix) (Matrix.determinant matrix) ; Js._false))
else fun ev -> (error_input_matrix() ; Js._false))
I want to do some calculs on a matrix, and the matrix is write by the user through a textarea with an html interface.
I think the problem is that the value of text1don't change, even if I write something in the textarea. Whatever the input on the textarea is, the result is the same.
Do anyone know how to use the value write by the user ?
Thanks !
Your probleme here is that you evaluate text1##value before defining the handler function, so the value is evaluated when the handler is installed, and then never changed. the following should works
btn1##onclick <- Dom_html.handler (
fun ev ->
if Matrix.is_matrix (Js.to_string text1##value)
then let matrix = Matrix.get_matrix (Js.to_string text1##value) in
(set_matrix_caracteristics (Matrix.nb_lines matrix) (Matrix.nb_columns matrix) (Matrix.determinant matrix) ; Js._false)
else error_input_matrix() ; Js._false
)
Related
we were hoping to use threads to get things going faster in an algorithm with many loops whose results are not interdependent.
within the code we hoped to port to rcpp, there is a call to model.matrix.
This did not appear straightforward to port.
Investigating this further (as to what code this runs for our use case), revealed that the S3 method for lm objects does some preparatory work on the variable and then calls the default version of the function as can be seen in this copy-paste of the code:
function (object, ...)
{
if (n_match <- match("x", names(object), 0L))
object[[n_match]]
else {
data <- model.frame(object, xlev = object$xlevels, ...)
if (exists(".GenericCallEnv", inherits = FALSE))
NextMethod("model.matrix", data = data, contrasts.arg = object$contrasts)
else {
dots <- list(...)
dots$data <- dots$contrasts.arg <- NULL
do.call("model.matrix.default", c(list(object = object,
data = data, contrasts.arg = object$contrasts),
dots))
}
}
}
the default version of the function farms at least some of its functionality out to a compiled C function:
function (object, data = environment(object), contrasts.arg = NULL,
xlev = NULL, ...) {
t <- if (missing(data))
terms(object)
else terms(object, data = data)
if (is.null(attr(data, "terms")))
data <- model.frame(object, data, xlev = xlev)
else {
reorder <- match(vapply(attr(t, "variables"), deparse2,
"")[-1L], names(data))
if (anyNA(reorder))
stop("model frame and formula mismatch in model.matrix()")
if (!identical(reorder, seq_len(ncol(data))))
data <- data[, reorder, drop = FALSE]
}
int <- attr(t, "response")
if (length(data)) {
contr.funs <- as.character(getOption("contrasts"))
namD <- names(data)
for (i in namD) if (is.character(data[[i]]))
data[[i]] <- factor(data[[i]])
isF <- vapply(data, function(x) is.factor(x) || is.logical(x),
NA)
isF[int] <- FALSE
isOF <- vapply(data, is.ordered, NA)
for (nn in namD[isF]) if (is.null(attr(data[[nn]], "contrasts")))
contrasts(data[[nn]]) <- contr.funs[1 + isOF[nn]]
if (!is.null(contrasts.arg)) {
if (!is.list(contrasts.arg))
warning("non-list contrasts argument ignored")
else {
if (is.null(namC <- names(contrasts.arg)))
stop("'contrasts.arg' argument must be named")
for (nn in namC) {
if (is.na(ni <- match(nn, namD)))
warning(gettextf("variable '%s' is absent, its contrast will be ignored",
nn), domain = NA)
else {
ca <- contrasts.arg[[nn]]
if (is.matrix(ca))
contrasts(data[[ni]], ncol(ca)) <- ca
else contrasts(data[[ni]]) <- contrasts.arg[[nn]]
}
}
}
}
}
else {
isF <- FALSE
data[["x"]] <- raw(nrow(data))
}
ans <- .External2(C_modelmatrix, t, data)
if (any(isF))
attr(ans, "contrasts") <- lapply(data[isF], attr,
"contrasts")
ans
}
is there some way of calling C_modelmatrix from Rcpp at all, whether it is single OR multi-threaded? Is there any library or package that does essentially the same thing from within Rcpp so I don't have to reinvent the wheel here? I'd rather not have to fully re-implement everything that model.matrix does if I can avoid it.
as we don't actually have functioning code, there isn't any to show for this yet.
The relevant portion of the function we were trying to speed up calls model.matrix like this: ("model.y is an lm", data are both copies of an original object returned by model.frame(model.y) )
ymat.t <- model.matrix(terms(model.y), data=pred.data.t)
ymat.c <- model.matrix(terms(model.y), data=pred.data.c)
this isn't really a results based question, more of an approach/methods based question
You can call model.matrix from within C++, but you cannot do so in a multi-threaded way.
There will also be overhead, but if the function call is needed deep within the middle of your code, it could be worth it as a convenience.
Example:
// [[Rcpp::export]]
RObject call(RObject x, RObject y){
Environment env = Environment::global_env();
Function f = env["model.matrix"];
RObject res = f(x,y);
return res;
}
I want to move an object in Haskell Gloss every frame a key is pressed, not just the one frame that the key is started being pressed. (Example: While 'w' key is pressed, accelerate object every frame)
Edit: I tried using the second parameter of EventKey but to no avail.
My code:
--TODO - Holding keys doesn't work yet
handleKeys :: Event -> AsteroidsGame -> AsteroidsGame
handleKeys (EventKey (Char char) _ _ _) game
| char == 'w' = move 0 1
| char == 'a' = move (-1) 0
| char == 's' = move 0 (-1)
| char == 'd' = move 1 0
where move x y = game {player = accelerateObject (player game) x y}
handleKeys _ game = game
accelerateObject :: Object -> Float -> Float -> Object
accelerateObject obj hor ver = obj {vel = (vx + hor, vy + ver)}
where (vx, vy) = vel obj
As OP correctly deduced, gloss gives you input events ("key was just pressed", "mouse was just moved"), rather than input state ("key is currently pressed", "mouse is at x,y"). There doesn't seem to be a built-in way to see input state on each frame, so we'll have to make our own workaround. Thankfully, this isn't too difficult!
For a simple working example, we'll make an incredibly fun "game" where you can watch a counter count upwards while the space bar is pressed. Riveting. This approach generalises to handling any key presses, so it'll be easy to extend to your case.
The first thing we need is our game state:
import qualified Data.Set as S
data World = World
{ keys :: S.Set Key
, counter :: Int }
We keep track of our specific game state (in this case just a counter), as well as state for our workaround (a set of pressed keys).
Handling input events just involves either adding a key to our set of currently pressed keys or removing it:
handleInput :: Event -> World -> World
handleInput (EventKey k Down _ _) world = world { keys = S.insert k (keys world)}
handleInput (EventKey k Up _ _) world = world { keys = S.delete k (keys world)}
handleInput _ world = world -- Ignore non-keypresses for simplicity
This can easily be extended to handle eg. mouse movement, by changing our World type to keep track of the last known coordinates of the cursor, and setting it in this function whenever we see an EventMotion event.
Our frame-to-frame world update function then uses the input state to update the specific game state:
update :: Float -> World -> World
update _ world
| S.member (SpecialKey KeySpace) (keys world) = world { counter = 1 + counter world }
| otherwise = world { counter = 0 }
If the spacebar is currently pressed (S.member (SpecialKey KeySpace) (keys world)), increment the counter - otherwise, reset it to 0. We don't care about how much time as elapsed between frames so we ignore the float argument.
Finally we can render our game and play it:
render :: World -> Picture
render = color white . text . show . counter
main :: IO ()
main = play display black 30 initWorld render handleInput update
where
display = InWindow "test" (800, 600) (0, 0)
initWorld = World S.empty 0
I am new to haskell
I have this program:
loop height weight=do
line<-getLine
if line=="1" then
do
height<-getLine
loop height weight
else if line=="2" then
do
weight<-getLine
loop height weight
else if line=="3" then
do
putStrLn (height)
else
do
putStrLn "error"
main :: IO ()
main = do
loop "" ""
It works fine,now I change it as this:
data A=A {height::String,weight::String}
loop::A->IO ()
loop z=do
line<-getLine
if line=="1" then
do
height<-getLine
let z.height=height
loop z
else if line=="2" then
do
weight<-getLine
let z.weight=weight
loop z
else if line=="3" then
do
putStrLn ((height z)++(weight z))
else
do
putStrLn "error"
main :: IO ()
main = do
let z=A "" ""
loop z
this program is wrong
I know in haskell and other function program there is no assignment，so let z.height=height is wrong,but I don't know how to write it right.I need some help,thanks!
You can use the record update notation:
if line=="1" then
do
height'<-getLine
loop z{height = height'}
Basically, z{height = height'} is a new record value, having the same fields as z except for the updated one. In this case, it is equivalent to A height' (weight z).
In Haskell you can say
main = do
let x = 5
print x
and this will not compile:
main = do
let x = 5
in print x
But if I am using explicit layout, this does not compile:
main = do {
let x = 5;
print x;
}
but this works:
main = do {
let x = 5
in print x;
}
Am I right? Is there anyplace I can read more about explicit layout and do and let notation? Section 3.14 of the Haskell 98 report seems to me to suggest that my third example should work, as it says I can write
do { let DECLS; stmts }
and it translates to
let DECLS in do { stmts }
The normative answer to your question can be found in the Haskell report's description of the layout rule.
Briefly, you need to place a semicolon between your let block and the next statement of the do block. That semicolon needs to lie outside of the let block. If you don't use layout for the let block, that's easy, just say:
let {x = 5};
However, if you do use layout for the let block, then the only way to close the let block is to start a line in a column before the column of x. So that means you'd have to write something like this:
main = do {
let x = 5
; print x;
}
Oh, and for your other example, again with layout a semicolon is getting inserted before the in, so your code desugars to:
main = do {
let {x = 5
};
in print x
}
Does anyone know of a truly declarative language? The behavior I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself)
The behavior I'm looking for is best shown with this pseudo code:
X = 10 // define and assign two variables
Y = 20;
Z = X + Y // declare a formula that uses these two variables
X = 50 // change one of the input variables
?Z // asking for Z should now give 70 (50 + 20)
I've tried this in a lot of languages like F#, python, matlab etc, but every time I tried this they come up with 30 instead of 70. Which is correct from an imperative point of view, but I'm looking for a more declarative behavior if you know what I mean.
And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically.
The code below would obviously work in C# but it's just so much code for the job, I'm looking for something a bit more to the point without all that 'technical noise'
class BlaBla{
public int X {get;set;} // this used to be even worse before 3.0
public int Y {get;set;}
public int Z {get{return X + Y;}}
}
static void main(){
BlaBla bla = new BlaBla();
bla.X = 10;
bla.Y = 20;
// can't define anything here
bla.X = 50; // bit pointless here but I'll do it anyway.
Console.Writeline(bla.Z);// 70, hurray!
}
This just seems like so much code, curly braces and semicolons that add nothing.
Is there a language/ application (apart from Excel) that does this? Maybe I'm no doing it right in the mentioned languages, or I've completely missed an app that does just this.
I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time.
Any Constraint Programming system will do that for you.
Examples of CP systems that have an associated language are ECLiPSe, SICSTUS Prolog / CP package, Comet, MiniZinc, ...
It looks like you just want to make Z store a function instead of a value. In C#:
var X = 10; // define and assign two variables
var Y = 20;
Func<int> Z = () => X + Y; // declare a formula that uses these two variables
Console.WriteLine(Z());
X = 50; // change one of the input variables
Console.WriteLine(Z());
So the equivalent of your ?-prefix syntax is a ()-suffix, but otherwise it's identical. A lambda is a "formula" in your terminology.
Behind the scenes, the C# compiler builds almost exactly what you presented in your C# conceptual example: it makes X into a field in a compiler-generated class, and allocates an instance of that class when the code block is entered. So congratulations, you have re-discovered lambdas! :)
In Mathematica, you can do this:
x = 10; (* # assign 30 to the variable x *)
y = 20; (* # assign 20 to the variable y *)
z := x + y; (* # assign the expression x+y to the variable z *)
Print[z];
(* # prints 30 *)
x = 50;
Print[z];
(* # prints 70 *)
The operator := (SetDelayed) is different from = (Set). The former binds an unevaluated expression to a variable, the latter binds an evaluated expression.
Wanting to have two definitions of X is inherently imperative. In a truly declarative language you have a single definition of a variable in a single scope. The behavior you want from Excel corresponds to editing the program.
Have you seen Resolver One? It's like Excel with a real programming language behind it.
Here is Daniel's example in Python, since I noticed you said you tried it in Python.
x = 10
y = 10
z = lambda: x + y
# Output: 20
print z()
x = 20
# Output: 30
print z()
Two things you can look at are the cells lisp library, and the Modelica dynamic modelling language, both of which have relation/equation capabilities.
There is a Lisp library with this sort of behaviour:
http://common-lisp.net/project/cells/
JavaFX will do that for you if you use bind instead of = for Z
react is an OCaml frp library. Contrary to naive emulations with closures it will recalculate values only when needed
Objective Caml version 3.11.2
# #use "topfind";;
# #require "react";;
# open React;;
# let (x,setx) = S.create 10;;
val x : int React.signal = <abstr>
val setx : int -> unit = <fun>
# let (y,sety) = S.create 20;;
val y : int React.signal = <abstr>
val sety : int -> unit = <fun>
# let z = S.Int.(+) x y;;
val z : int React.signal = <abstr>
# S.value z;;
- : int = 30
# setx 50;;
- : unit = ()
# S.value z;;
- : int = 70
You can do this in Tcl, somewhat. In tcl you can set a trace on a variable such that whenever it is accessed a procedure can be invoked. That procedure can recalculate the value on the fly.
Following is a working example that does more or less what you ask:
proc main {} {
set x 10
set y 20
define z {$x + $y}
puts "z (x=$x): $z"
set x 50
puts "z (x=$x): $z"
}
proc define {name formula} {
global cache
set cache($name) $formula
uplevel trace add variable $name read compute
}
proc compute {name _ op} {
global cache
upvar $name var
if {[info exists cache($name)]} {
set expr $cache($name)
} else {
set expr $var
}
set var [uplevel expr $expr]
}
main
Groovy and the magic of closures.
def (x, y) = [ 10, 20 ]
def z = { x + y }
assert 30 == z()
x = 50
assert 70 == z()
def f = { n -> n + 1 } // define another closure
def g = { x + f(x) } // ref that closure in another
assert 101 == g() // x=50, x + (x + 1)
f = { n -> n + 5 } // redefine f()
assert 105 == g() // x=50, x + (x + 5)
It's possible to add automagic memoization to functions too but it's a lot more complex than just one or two lines. http://blog.dinkla.net/?p=10
In F#, a little verbosily:
let x = ref 10
let y = ref 20
let z () = !x + !y
z();;
y <- 40
z();;
You can mimic it in Ruby:
x = 10
y = 20
z = lambda { x + y }
z.call # => 30
z = 50
z.call # => 70
Not quite the same as what you want, but pretty close.
not sure how well metapost (1) would work for your application, but it is declarative.
Lua 5.1.4 Copyright (C) 1994-2008 Lua.org, PUC-Rio
x = 10
y = 20
z = function() return x + y; end
x = 50
= z()
70
It's not what you're looking for, but Hardware Description Languages are, by definition, "declarative".
This F# code should do the trick. You can use lazy evaluation (System.Lazy object) to ensure your expression will be evaluated when actually needed, not sooner.
let mutable x = 10;
let y = 20;
let z = lazy (x + y);
x <- 30;
printf "%d" z.Value