## 526 Reputation

16 years, 73 days

## Disagreement with Maple...

I present the following:
``````[> restart;
[> a1:= foo = bar;
a1 := foo = bar
[> a2:= blam = foo = bar;
Error, `=` unexpected
[> a3:= blam = a1;
a3 := blam = (foo = bar)
``````
The fact that the definition of `a2` (correctly) throws an error and the definition of `a3` does not can lead to some odd errors down the way. I disagree with Maple's choice not to say that the assignment of `a3` is in error.

## Interesting numeric bug...

The student is supposed to use the logistic differential equation given to them (with carrying capacity `.52e12`), `dsolve()` the differential equation with a specific initial condition, and then calculate the population at 3 different times. Notice what happens:
``````
[> restart;
[> my_deq := (diff(P(t), t))/P(t) = .789*(1-P(t)/(.52*10^12));

d
-- P(t)
dt                               -11
my_deq := ------- = 0.789 - 0.1517307692 10    P(t)
P(t)

[> dsolve({my_deq,P(2290)=.83*10^10});
``````

## Escaped local variables and odd behaviou...

I think that I will start moving to file all of my bug/error/oversight complaints in blog entries. This way (in theory), they are more easily indexed on this site. So, I was playing around with a procedure today: ```[>restart; testproc:= proc(Q::`=`) local a; ##IF STATEMENT## return a; end proc: [> ``` The if statement noted in the procedure always took on the following appearance: `if #Check if lhs(Q)=a# then #assign rhs(Q) to a#;fi;` Writing my procedure as above ensured that the `restart` would be executed every time I changed my if statement. My first if statement went like this:

## 1 Shortcoming and 1 bug in 2D Input, Map...

First, the shortcoming: Open a new Maple worksheet (I always work in Worksheet mode, so I haven't tested what happens in Document mode), and type anything in 2D Math Input into a line but do not execute that line. Save the file, then open it in a text editor or word processor. If you scroll down to the line containing the information for what you just typed in, you will notice that the attribute "input-equation" will be null; that is, it should say `input-equation=""` Even though there is input on the line, Maple doesn't add anything to the "input-equation" attribute until the commands are executed.

## New way to crash solve()...

Students do the craziest things. This was an interesting bug to run into. The following lines all cause Maple 11 to lose connection with its kernel: ```solve( x-x = 0 ); solve( x-x = 1 ); solve( x-x = -1 ); ``` Whereas, the following lines do not cause Maple 11 to lose connection with its kernel: ```solve( 1=0 ); solve( x-x+1 = 0 ); solve( x-x-1 = 0 ); solve( x=x+1 ); solve( (x-x)^2 = 0 ); solve( x-x = x ); ``` This message has also been sent to support@maplesoft.com
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