Is there a way to nest for loops inside other for loops in Pari/GP (2.7.6) since the following error always appears:
*** at top-level: read("prog.txt")
*** ^----------------
*** read: sorry, embedded braces (in parser) is not yet implemented.
Code:
(12:14) gp > n = 12
%12 = 12
(12:14) gp > k = 10
%13 = 10
(12:14) gp > g = [1..10]
%14 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
{
forprime(p = 1, 16,
rn = n%p
rk = k%p
{
for(i=1, #g,
if( (rn*(g[i]+rk)+1)%p!=0,
h = concat(h, g[i])
}
g = h
}
Thanks for help. The question where I posted and got the code from got deleted, so I'm kind of stuck at this point.
Braces don't mean the same thing as in C# or many other programming languages. They do not start/end a block.
In PARI multiple statements are joined with a semi-colon and contained within the argument parenthesis of a function. Special functions include while, for, if etc.
For example:
my(s=7);forprime(p=1, 7, s*=3; for(i=1, p, s+=p^2); s+=6); s
contains three statements inside the forprime loop, separated by semicolons and one of those is another loop.
Now braces {} on the other hand, just allow you to write programs that are more than one line long. Normally when an end of line is reached, PARI tries to interpret everything on that line. But it doesn't do that if between { and }, so you never need more than one pair.
In your example you need to remove the inner {} and add some semi-colons between statements.
Related
I'm a very new to lua so am happy to read material if it will help with tables.
I've decoded a json object and would like to build a table properly using its data, rather than writing 64 lines of the below:
a = {}
a[decode.var1[1].aId] = {decode.var2[1].bId, decode.var3[1].cId}
a[decode.var1[2].aId] = {decode.var2[2].bId, decode.var3[2].cId}
a[decode.var1[3].aId] = {decode.var2[3].bId, decode.var3[3].cId}
...etc
Because the numbers are consecutive 1-64, i presume i should be able to build it using a for loop.
Unfortunately despite going through table building ideas I cannot seem to find a way to do it, or find anything on creating nested tables using a loop.
Any help or direction would be appreciated.
Lua for-loops are, at least in my opinion, pretty easy to understand:
for i = 1, 10 do
print(i)
end
This loop inclusively prints the positive integers 1 through 10.
Lua for-loops also take an optional third argument--which defaults to 1--that indicates the step of the loop:
for i = 1, 10, 2 do
print(i)
end
This loop prints the numbers 1 through 10 but skips every other number, that is, it has a step of 2; therefore, it will print 1 3 5 7 9.
In the case of your example, if I understand it correctly, it seems that you know the minimum and maximum bounds of your for loops, which are 1 and 64, respectively. You could write a loop to decode the values and put them in a table like so:
local a = {}
for i = 1, 64 do
a[decodevar.var1[i].aId] = {decode.var2[i].bId, decode.var3[i].cId}
end
What you can do is generating a new table with all the contents from the decoded JSON with a for loop.
For example,
function jsonParse(jsonObj)
local tbl = {}
for i = 1, 64 do
a[decodevar.var1[i].aId] = {decode.var2[i].bId, decode.var3[i].cId}
end
return tbl
end
To deal with nested cases, you can recursively call that method as follows
function jsonParse(jsonObj)
local tbl = {}
for i = 1, 64 do
a[decodevar.var1[i].aId] = {decode.var2[i].bId, decode.var3[i].cId}
if type(decode.var2[i].bId) == "table" then
a[decodevar.var1[i].aid[0] = jsonParse(decode.var2[i].bId)
end
end
end
By the way, I can't understand why are you trying to create a table using a table that have done the job you want already. I assume they are just random and you may have to edit the code with the structure of the decodevar variable you have
In this example dataset i have created a column called 'Var'. This is the result i would like from a the code. The pseudo-code to give Var is like this : For each ID_Survey, compare the Distance in sequence, if the difference between sequential Distances is 10, then Var=1, otherwise Var=0. Var should be 1 for both elements of the sequence where the difference is 10.
#Generate data
ID_Survey=rep(seq(1,3,1),each=4)
Distance= c(0,25,30,40,50,160,170,190,200,210,1000,1010)
Var= c(0, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1);
TestData=data.frame(cbind(ID_Survey,Distance,Var))
TestData
I can use a simple for-loop like this, which nearly works, but it trips-up when moving between ID_Survey.
for(i in 1:(nrow(TestData)-1)){
TestData$Var2[i]=(TestData$Distance[i+1]==TestData$Distance[i]+10)}
I need to incorporate the above into a function which splits the data.frame into groups based on ID_Survey. I'm trying to build something like the following...
New6=do.call(rbind, by(TestData,list(TestData$ID_Survey),
FUN=function(x)
for (i in nrow(x)){ #loop must build an argument then return it.
#conditional statements in here.
return(x[i,])})); #loop appears to return 1st argument only.
... but i can't get the for-loop to operate inside the by-statement.
Any guidance much appreciated. Many thanks.
Using the data.table function (.SD) manages separating and collating chunks of the data.frame (as defined by ID_Survey) after it has been sent to a function. No doubt someone else will have a more elegant solution, but this seems to do the job:
library(data.table)
ComPair=function(a,b){V=ifelse(a==b-10,TRUE,FALSE);return(V)}
TestFunction=function(FData){
if(nrow(FData)>1){
for(i in 1:(nrow(FData)-1)){
V=ComPair(FData$Distance[i],FData$Distance[i+1])
if(V==1){ FData$Var2[i]=V;FData$Var2[i+1]=V}
}
};return(FData)}
TestData_dt=data.table(TestData)
TestData2=TestData_dt[,TestFunction(.SD),ID_Survey]
TestData2
I'm trying to write predicate range\3 that takes three parameters the first is the start, the second is the end and return the generated list in the third argument.
E.g rang(1,5,L).
L = [1, 2, 3, 4, 5]
I used this code
range(E,E,[E]).
range(S,E,L):-
S1 is S + 1,
range(S1,E,[S|L]).
But it does not work, when i used trace command to know where is the error i recognized that the base case is useless, I also tried the green cut !in the base case but it does not work range(E,E,[E]),!.
So, if any one knows what is the problem please help me
You're building the list in 'wrong' sense. Consider that when you'll call the base case, it will receive the consed list. How could match a single element list ? Try instead
range(S,E,[S|L]):-
S1 is S + 1,
range(S1,E,L).
This question already has answers here:
'pass parameter by reference' in Ruby?
(6 answers)
Closed 8 years ago.
How can I change the contents of a variable using a method? Maybe I'm not saying this correctly. What is a way to get the reference to a variable like in C? Example:
// main stuff
int gorilla = 29;
makeMeABanana(&gorilla);
void makeMeABanana(int *gorilla) { }
How can I do something like this in Ruby?
You should not do this - you're just porting techniques that are fully appropriate to C to Ruby, where they are no longer appropriate. There are several fancy ways around this (eg using a Proc closed over your calling namespace, or eval) but they are usually inappropriate in Ruby unless you know precisely what you're doing.
Recently on the ruby-talk mailing list, someone asked about writing a swap function where swap(a,b) would swap the values of the variables "a" and "b". Normally this cannot be done in Ruby because the swap function would have no reference to the binding of the calling function.
However, if we explictly pass in the binding, then it is possible to write a swap-like function. Here is a simple attempt:
def swap(var_a, var_b, vars)
old_a = eval var_a, vars
old_b = eval var_b, vars
eval "#{var_a} = #{old_b}", vars
eval "#{var_b} = #{old_a}", vars
end
a = 22
b = 33
swap ("a", "b", binding)
p a # => 33
p b # => 22
This actually works! But it has one big drawback. The old values of "a" and "b" are interpolated into a string. As long as the old values are simple literals (e.g. integers or strings), then the last two eval statements will look like: eval "a = 33", vars". But if the old values are complex objects, then the eval would look like eval "a = #", vars. Oops, this will fail for any value that can not survive a round trip to a string and back.
Referred from : http://onestepback.org/index.cgi/Tech/Ruby/RubyBindings.rdoc
Integers are objects, with an id, like everything else in Ruby. They are implemented like this:
p (0..10).map{|n| n.object_id}
#=>[1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21]
All other objects have even object_id numbers. There is no way to change 7 (object_id 15) into something else.
How can I mock an array's sort expect a lambda expression?
This is a trivial example of my problem:
# initializing the data
l = lambda { |a,b| a <=> b }
array = [ 1, 2, 3, 4, 5 ]
sorted_array = [ 2, 3, 8, 9, 1]
# I expect that sort will be called using the lambda as a parameter
array.expects(:sort).with( l ).returns( sorted_array )
# perform the sort using the lambda expression
temp = array.sort{|a,b| l.call(a,b) }
Now, at first I expected that this would work; however, I got the following error:
- expected exactly once, not yet invoked: [ 1, 2, 3, 4, 5 ].sort(#<Proc:0xb665eb48>)
I realize that this will not work because l is not passed as a parameter to l. However, is there another way to do what this code is trying to accomplish?
NOTE: I have figured out how to solve my issue without figuring out how to do the above. I will leave this open just in case someone else has a similar problem.
Cheers,
Joseph
Mocking methods with blocks can be quite confusing. One of the keys is to be clear about what behaviour you want to test. I can't tell from your sample code exactly what it is that you want to test. However, you might find the documentation for Mocha::Expectation#yields (or even Mocha::Expectation#multiple_yields) useful.