Best way of Stacks in Rascal? - rascal

I am sure Rascal has built in support for Stack (e.g. for expression eval via stack push/pop), but I cannot find anything.
So I now use this. However is there a nicer way?
list stack = [];
pop:
value = stack[size(stack)-1];
stack = stack - value;
push
stack = stack + value

I'd recommend changing pop to:
value = stack[-1]; //short hand notation
stack = delete(stack, size(stack)-1); // to make sure the last item is deleted (in case duplicates exist in the list)

Have a look at the documentation of the
List module: lists support a whole zoo of stack-related functions: push, pop, top, dup, etc.

Related

Lua - table won't insert from function

I have a Lua function where I build a table of value and attempt to add it to a global table with a named key.
The key name is pulled from the function arguments. Basically, it's a filename, and I'm pairing it up with data about the file.
Unfortunately, the global table always comes back nil. Here's my code: (let me know if you need to see more)
(Commented parts are other attempts, although many attempts have been deleted already)
Animator = Class{}
function Animator:init(atlasfile, stringatlasfriendlyname, totalanimationstates, numberofframesperstate, booleanstatictilesize)
-- Define the Animator's operation mode. Either static tile size or variable.
if booleanstatictilesize ~= false then
self.isTileSizeStatic = true
else
self.isTileSizeStatic = false
end
-- Define the total animation states (walking left, walking right, up down, etc.)
-- And then the total frames per state.
self.numAnimationStates = totalanimationstates or 1
self.numAnimationFrames = numberofframesperstate or 2
-- Assign the actual atlas file and give it a programmer-friendly name.
self.atlasname = stringatlasfriendlyname or removeFileExtension(atlasfile, 'animation')
generateAnimationQuads(atlasfile, self.atlasname, self.numAnimationStates, self.numAnimationFrames)
end
function generateAnimationQuads(atlasfile, atlasfriendlyname, states, frames)
spriteWidthDivider = atlasfile:getWidth() / frames
spriteHeightDivider = atlasfile:getHeight() / states
animationQuadArray = generateQuads(atlasfile, spriteWidthDivider, spriteHeightDivider)
animationSetValues = {atlasarray = animationQuadArray, width = spriteWidthDivider, height = spriteHeightDivider}
--gAnimationSets[#gAnimationSets+1] = atlasfriendlyname
gAnimationSets[atlasfriendlyname] = animationSetValues
--table.insert(gAnimationSets, atlasfriendlyname)
end
Note: when using print(atlasfriendlyname) and print(animationSetValues), neither are empty or nil. They both contain values.
For some reason, the line(s) that assign the key pair to gAnimationSets does not work.
gAnimationSets is defined a single time at the top of the program in main.lua, using
gAnimationSets = {}
Animator class is called during the init() function of a character class called Bug. And the Bug class is initialized in the init() function of StartState, which extends from BaseState, which simply defines dummy init(), enter(), update() etc. functions.
StartState is invoked in main.lua using the StateMachine class, where it is passed into StateMachine as a value of a global table declared in main.lua.
gAnimationSets is declared after the table of states and before invoking the state.
This is using the Love2D engine.
Sorry that I came here for help, I've been picking away at this for hours.
Edit: more testing.
Trying to print the animationQuadArray at the index gTextures['buganimation'] always returns nil. Huh?
Here's gTextures in Main.lua
gTextures = {
['background'] = love.graphics.newImage('graphics/background.png'),
['main'] = love.graphics.newImage('graphics/breakout.png'),
['arrows'] = love.graphics.newImage('graphics/arrows.png'),
['hearts'] = love.graphics.newImage('graphics/hearts.png'),
['particle'] = love.graphics.newImage('graphics/particle.png'),
['buganimation'] = love.graphics.newImage('graphics/buganimation.png')
}
Attempting to return gTextures['buganimation'] returns a file value as normal. It's not empty.
My brain is so fried right now I can't even remember why I came to edit this. I can't remember.
Global table in Main.lua, all other functions can't access it.
print(gTextures['buganimation']) works inside the function in question. So gTextures is absolutely accessible.
Table isn't empty. AnimationSetValues is not empty.
I'm adding second answer because both are correct in context.
I ended up switching IDE's to VS Code and now the original one works.
I was originally using Eclipse LDT with a Love2D interpreter and in that environment, my original answer is correct, but in VS Code, the original is also correct.
So Dimitry was right, they are equivalent, but something about my actual Eclipse setup was not allowing that syntax to work.
I switched to VS Code after I had another strange syntax problem with the interpreter where goto syntax was not recognized and gave a persistent error. The interpreter thought goto was the name of a variable.
So I switched, and now both things are fixed. I guess I just won't use LDT for now.
Solution: Lua syntax. Brain Fry Syndrome
I wrote:
animationSetValues = {atlasarray = animationQuadArray, width = spriteWidthDivider, height = spriteHeightDivider}
Should be:
animationSetValues = {['atlasfile']=atlasfile, ['atlasarray']=animationQuadArray, ['width']=spriteWidthDivider, ['height']=spriteHeightDivider}
Edit: I'm fully aware of how to use answers. This was posted here to reserve my spot for an answer so I could edit it later when I returned back home, which is exactly what I'm doing right now. I'll keep the old post for archival purposes.
Original:
I solved it. I apologize for not posting the solution right now. My brain is melted into gravy.
I will post it tomorrow. Just wanted to "answer" saying no need to help. Solved it.
Solution is basically, "oh it's just one of those Lua things". Wonderful. I'm having so much fun with this language - you can tell by my blank expression.
From the language without line endings or brackets, but forced print parentheses... ugh. I'm going back to C# when this class is done.

Adding labels to my programming language

Actually I am writting a programming language in Lua. It was quite fun. I've wrote a bit of standard library (stack op and simple io). Then I've thought about labels. It would look like in assembly. While and for loop aren't funny in any bit so programming in that language can be quite challenging. Here are some requirements for this system:
Label stack (or array, dictionary) must be accessible from global context.
Jump instruction handler will be in separate file.
This is how my label-handling function look like:
function handleLabel(name,currentLine)
end
I have no idea how to implement this kind of magic. First I've thought about that:
LabelLineIDS = {}
Labels = {}
Labelamount = 1;
function handleLabel(name,currentLine)
LabelLineIDS[Labelamount]=currentline
Labels[Labelamount]=name
Labelamount=Labelamount+1
end
-- In file "jump.lua":
local function has_value (tab, val)
for index, value in ipairs(tab) do
if value == val then
return index
end
end
print ("Error: Label not defined.") -- Bail out.
os.exit(1)
end
local function _onlabel()
local labelName = globalparams --Globalparams variable contain parameters to each function, at the moment
--this will contain label name. It _can_ be nil.
return LabelLineIDS[has_value(Labels, labelName)]
end
CurrLine = _onlabel() --Currline - current line that get's parsed.
--1 command per one line.
But I'm unsure is this well written or even work. Can you give me idea how to parse labels in my programming language (and write jump functions)? Or if my code is pretty ok at the moment, can you help me to improve it?
Using line counter in my parser I've decided to implement gotos like we can see in BASIC. Thanks everyone for help.

Open/Libre Office macro to scroll view to selection

In Writer, I would like to search for some text and when found position the view to the top of the view/window.
Using the following code,
document = ThisComponent.CurrentController.Frame
dispatcher = createUnoService("com.sun.star.frame.DispatchHelper")
dim args1(1) as new com.sun.star.beans.PropertyValue
args1(0).Name = "SearchItem.SearchString"
args1(0).Value = ":"
dispatcher.executeDispatch(document, ".uno:ExecuteSearch", "", 0, args1())
the view changes and it shows the selection but it is not in any particular place. I want it to be at the top of the window/view.
I've also found elsewhere the use of ThisComponent.currentController.getViewData() and restoreViewData(). So I experimented and determined how to change the data returned in order to get a vertical scroll but nothing happens. For example...
vd = ThisComponent.currentController.getViewData()
vdParts = Split(vd, ";")
vdParts(6) = CLng(vdParts(6)) + 1000
vd = join(vdParts, ";")
ThisComponent.currentController.restoreViewData(vd)
Any suggestions?
PS: I am running version 5.0.5.2 on Windows 7 x64
Spreadsheets have View Panes that can be manipulated, but it does not look like there is a similar interface in Writer.
Instead, use the View Cursor to go down one or two pages, then move back to the location of the search result.
Also, do not use the dispatcher for the search. Use the API instead, like in section 7.14 of Andrew Pitonyak's macro document.

How to determine if a Dart list is a fixed list?

How can I determine, at runtime, if a list in Dart is a "fixed list" ?
There are (at least) three ways to create a fixed-length list in Dart:
var fixed = new List(5); // fixed at five elements
var alsoFixed = new List.filled(5, null); // fixed at five elements, set to null
var fixedToo = new List.from([1,2,3], growable: false);
How do I ask, in code, if fixed, alsoFixed, and fixedToo are fixed-length?
You can try to add an element and remove it to know if the list has a fixed length:
bool hasFixLength(List list) {
try {
list
..add(null)
..removeLast();
return false;
} on UnsupportedError {
return true;
}
}
runtimeType can be used for that, but shouldn't because it's not very reliable especially with dart2js otherwise there isn't. AFAIR there were several requests to add support for this but was declined.
We did not add any way to see if a list is fixed (or const).
So far, we have only encountered one use case where this would fit into well-written code: checking that a function returned a mutable array. We decided that this use case was not worth changing the API.
Most of the time, an additional boolean flag that asks to modify an existing list is cleaner (since then, the caller can decide what the callee should do).
If you have another use case, please let us know and we will investigate.

How To Do OpenSCAD Stack-Like Operations?

I'm pretty new to OpenSCAD, but have got most of it down. However, I'm not sure how I can do stack-like operations. It doesn't really matter what data structure is used, as long as I can push and pop numbers. Is this possible?
I worked extensively with stacks while implementing a string processing library.
The trick is to use nested right associative lists of size = 2, e.g. ["foo", ["bar", []]].
If you want to push something to a stack:
function push(stack, item) = [item, stack];
If you want to pop the stack:
function pop(stack) = stack[1];
And if you want to peek or retrieve the value that was popped:
function peek(stack) = stack[0];
You can also implement map/reduce functions using recursion:
function map(stack) =
push(
map(pop(stack)),
f(peek(stack))
);
function reduce(stack) =
f(peek(stack))?
push(
reduce(pop(stack)),
f(peek(stack))
)
:
reduce(pop(stack))
;
Of course, now that version 2015.03 is out you might consider using list comprehension, assuming that's what you really need.

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