Combining AND + OR Statements

[Kathleen Hupfeld]

Hi all,

Quick question I am tripping up on: if I use this syntax

replace XXX = XXX if var1 < 100 & var2 == 2000 | var3 == 3000

Does this do the replacement based on the var1 AND the var2 OR the var3 statement? i.e., I want the var1 to be true for it to replace, and then I want either the var2 OR the var3 to be true to replace.

I believe that if I reordered to this, it does not work as intended. I.e., it doesn't group var2/3 together. I think it instead needs either var2==2000 and then var3==3000 AND var1<100 to be true.

replace XXX = XXX if var2 == 2000 | var3 == 3000 & var1 < 100

[Kathleen Hupfeld]

Edit: I think it will only work as intended if I use parentheses:

replace XXX = XXX if var1 < 100 & (var2 == 2000 | var3 == 3000)

[Nick Cox]

Here's the paragraph that explains everything:

13.2.5 Order of evaluation, all operators

The order of evaluation (from first to last) of all operators is ! (or ~), ^, - (negation), /, *, - (subtraction), +, != (or ~=), >, <, <=, >=, ==, &, and |.

That said, I would fail a test based on whether I knew all of that. Here are some small slogans:

Check with little examples where you can work out the correct answer quickly: display and Mata are your friends.

If it does not work as expected, then you probably got it wrong, so test your code to find out. .

If uncertain, parenthesise aggressively.

[Kathleen Hupfeld]

Thank you Nick!!! Very helpful.