Code of today.

I'm getting to use the ultimate power of the '\' more and more.

It really look and feels like java streams, but no lambdas to be seen!

A side effect seams to be that I tend to close a lot of lines with a pile of parenthesis, since there is only one natural indentation level.

Look for example to the Folds function!

```
Point = Data.AddList:Data:{I x, I y}
Folds = {class method Point.List (S that)=\()((
ss=that.split(S.nl()++S.nl())
_=ss()
for line in ss().split(S.nl()) (
isY = line.startsWith(S"fold along y=")
if isY \add(\(x=0I,y=ReadFold(line)))
else \add(\(x=ReadFold(line),y=0I))
)))}
Max={class method Point (Point.List that)=(
var maxX = 0I
var maxY = 0I
for (x,y) in that (
if x>maxX (maxX:=x)
if y>maxY (maxY:=y)
)
Point(x=(maxX*2I)+1I,y=(maxY*2I)+1I)
)}
ReadFold ={class method I(S that)=(
(size) = S"fold along y="
I(string=that.subString(size to=\size))
)}
Matrix = (
input = Fs.Real.#$of().read(\"input")
ps = Folds(input)
(x,y) = Max(ps)
Collection.matrix(I.List,row=y, col=x)
)
Fold={
class method Void (mut Matrix m, Point range, Point fold)=(
(x,y) = fold
if x==0I \y(m=m,range=range,fold=y)
else \x(m=m,range=range,fold=x)
)
class method Void x(mut Matrix m, Point range, I fold)=(
for xi in Range(fold),
xj in Range(fold+1I,to=(fold*2I)+1I).reverse() (
for y in Range(range.y()) (
new = m.val(row=y col=xi)+m.val(row=y col=xj)
m.set(row=y col=xi val=new)
m.set(row=y col=xj val=0I)
)
)
)
class method Void y(mut Matrix m, Point range, I fold)=(
for yi in Range(fold),
yj in Range(fold+1I,to=(fold*2I)+1I).reverse() (
for x in Range(range.x()) (
new = m.val(row=yi col=x)+m.val(row=yj col=x)
m.set(row=yi col=x val=new)
m.set(row=yj col=x val=0I)
)
)
)
}
Main=(
input = Fs.Real.#$of().read(\"input")
ps = Folds(input)
range = Max(ps)
(x,y) = range
m = Matrix(\()(
for xi in Range(x), for yi in Range(y) \add(0I)
))
ss = input.split(S.nl()++S.nl())
for line in ss().split(S.nl()) (
s=line.split(S",")
xi = I(string=s())
yi = I(string=s())
m.set(row=yi col=xi val=1I)
)
folds = Point.List()(for line in ss().split(S.nl()) (
isY = line.startsWith(S"fold along y=")
if isY \add(\(x=0I,y=ReadFold(line)))
else \add(\(x=ReadFold(line),y=0I))
))
for f in folds i in Range(folds.size())(
Fold(m=m,range=range,fold=f)
)
for yi in Range(7I)(//7 and 41 are just reasonable sizes :-/
Debug(S"".builder()(for xi in Range(41I) \add(
if m.val(row=yi,col=xi)==0I S" " else S"#"
)))//CEJKLUGJ
)
)
```

What have I learnt?

-Matrix need to have class methods giving you the max range!

-Matrix need to have a functionality to be initialized with a single value in all cells.

-There is no easy way to print a char without going new line, so in the solution I had to accumulate on a full line string before printing... is this ok? should I have Debug.print(..) to not go new line?

You can find the 42 tutorial in video form at

(https://www.youtube.com/watch?v=Xsz5yxNR_Vo&list=PLWsQqjANQic8c5wG3LfSe-mMiBKfOtBFJ)

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