Why is mathcad altering this vector when the IF conditions are not met?

Question

I have a loop with two conditions in it, none of which are satisfied.

I created a variable 'a' and defined it as zero, and inside the loop, I made it change 'a' to 1 if the If conditions are satisfied. as shown in the figure below, a is still zero after the loop, meaning the conditions are not satisfied. However, the vector y4 is modified even though it only has equations to modify it inside the same conditions for variable 'a', which is unchanged:

what am I missing here?

I attached the file. Using Mathcad Prime 9.0.00

thanks

terryhendicott · Accepted Answer

Lets keep to this simplification of your example:

what exactly is setting the variables to zero in your example? good question

Prime has to make a distinction if "a" in the program is the global "a" defined above the program or a local "a" within the program.

"a" if passed into the program as a parameter then it is clearly a global one.

"a" if not defined on the left hand side of a assignment but is used on the right hand side of an assignment it is the global one.

In your arrangement "a" within the program is set as output to the "a" global one on completion of the program. It is still not clear if it is "a" local or "a" global within the program. You are assuming it is the global "a" and is thus defined in all cases.

Prime makes "a" within the program a local variable as it does not know any different and it has to make an assumption. 0 is the default value that is set to this "a" local variable as no condition sets it value to any other value. So it returns "a" local as zero.

If you want it to be the global "a" do it like this

Cheers

Terry

LucMeekes · Answer

Note that both a and y4 are 0 after the loop.What if you set a:=2 before the loop. Is it still 2 afterwards? Success!Luc

Sign up

Please use your PTC eSupport account.

Welcome to the PTC Community

Please use your PTC eSupport account.

Scanning file for viruses.

This file cannot be downloaded