openscad If statement issue with variable

Question

I have a problem with If statement in OpenScad. I have 4 variables

a=20;
b=14;
w=1;
c=16;

I want to check witch number is bigger a or b. And after depending who is smaller to take the value of smaller variable(in our case b < a) and to make a simple operation with c variable ( c=b-w).

I tried like this but it doesn't work.

a=20;
b=14;
w=1;
c=16;
if(a>b)
{
    c=b-w;
}

if (a<b)
{
c=a-w;
}

if (a==b)
{
c=a-w;
}

It seems logic, but in openscad as I understood you can't change the value of variable inside a If statement. What trick can I use in order to get my goal. Thank you!

Answer 1

in the 3. leg you confused the assignment-operator „=“ with the equal-operator „==“ (correct if (a==b)). in your 3. leg you do the same as in the 2., so you could handle both as an „else“-leg.

Correct: assignment is not allowed in if-statement. In openscad you can use the ? operator instead:

c = a > b ? b-w : a-w;

After = follows the condition. The statement after the ? becomes the value if the condition is true, and the statement after the : becomes the value if the condition is false. Nested conditions are possible, e.g. your conditions:

c = a > b ? b-w : (a < b ? a-w : a-w);

More information in the documentation.