brett knoss (May 30 2021 at 00:32): brett knoss (May 30 2021 at 00:32):function d(x,y)
x=3
y=8
end
d(dog,cat)
This doesn't recognize dog as a variable
how do I get dog=3, cat=8
?
Brenhin Keller (May 30 2021 at 00:38):dog = 3; cat = 8?
or if you want to be fancy
dog, cat = 3, 8
But whether or not that's something you want to to do maybe depends on what you're ultimately trying to accomplish
Mason Protter (May 30 2021 at 01:03):It sounds like you're trying to run a function inside out. That's now how the data flows. When you write d(dog, cat), julia looks up what values are associate with the variables dog and cat and then passes those variables into the function d.
Inside the function, you then bind those values to the arguments, x and y, but then inside the function body you then rebind x and y to 3 and 8, completely ignoring whatever values were passed in
Mason Protter (May 30 2021 at 01:07):If you want d to assign the values 3 and 8 to new variables dog and cat, then you can't do that with a function, but you can do it using a macro.
julia> macro d(x, y)
ex = quote
$x = 3
$y = 8
end
esc(ex)
end
@d (macro with 1 method)
julia> @d(dog, cat)
8
julia> dog + cat
11
That works, but apparently I can't do the same thing in a dataframes, or maybe I'm trying to send data both ways
macro transaction(newdate,newcredit,credit_amount,newdebit, debit_amount)
if credit_amount != debit_amount
"Error--Debit and Credit must match"
else
ex= quote
newtransaction = DataFrame(
$newdate=[newdate]
$newcredit = [credit_amount],
$newdebit = [debit_amount])
end
esc(ex)
end
end
Macros are not like functions. They just operate on syntax.
brett knoss (May 30 2021 at 01:36):Ok, so do I then need to somehow have a macro and a function?
Mason Protter (May 30 2021 at 01:38):I would recommend just writing a function and no macro.
Mason Protter (May 30 2021 at 01:39):And then just writing
new_transaction = transaction(newdate,newcredit,credit_amount,newdebit, debit_amount)
instead of trying to write a macro
Mason Protter (May 30 2021 at 01:41):If you really want a macro for this though, I guess you could write
julia> using DataFrames
julia> macro transaction(newdate,newcredit,credit_amount,newdebit, debit_amount)
ex= quote
if $credit_amount != $debit_amount
"Error--Debit and Credit must match"
else
newtransaction = $DataFrame(
newdate=[$newdate],
newcredit = [$credit_amount],
newdebit = [$debit_amount]
)
end
end
esc(ex)
end
@transaction (macro with 1 method)
julia> @transaction(1, 2, 3, 4, 3)
1×3 DataFrame
Row │ newdate newcredit newdebit
│ Int64 Int64 Int64
─────┼──────────────────────────────
1 │ 1 3 3
macro transaction(newdate,newcredit,credit_amount,newdebit, debit_amount)
ex= quote
if $credit_amount != $debit_amount
"Error--Debit and Credit must match"
else
newtransaction = $DataFrame(
Date=[$newdate],
$newcredit = [4],
$newdebit = [4]
)
end
end
esc(ex)
end
@transaction("Jan 1, 1900", chequing, 3, personal, 3)
won't let me add a variable, but I'm not sure which one.
wo
Last updated: Oct 24 2025 at 04:41 UTC