Entry #10 Reading my peers' slogs

I think this week's materials are the hardest ever. Danny introduced some terminologies such as computability,  diagonalization,  and .countability. I find these definitions are ambiguous and confusing.. When I read my peers' slog, I find that several people have same question as me. They also feel that the materials are challenging.

When I read Matt Cheung's slog, he gives some examples to distinguish well-defined functions from not well-defined function. I feel that it is very clear.

• well defined: x = {1, 2, 3, 4}, y  = {a, b, c, d}

• not well defined: x = {1, 2, 3}, y = {a, b, c, d}
• not well defined: x = {1, 2, 3, 4}, y = {a, b, c}

Danny said that well-defined functions have to be 1-1 and onto. The last two example violate 1-1 and onto respectively. Therefore, they are not well-defined function.

In the Lukas Frantzke's slog, he/she talked about his./her opinion about infinite loop. He/she mentioned that infinite loop is different from long running time. Sometime it is very hard to tell which one the program counters. Last year, when I took csc108, some program that I wrote took more than 3 minutes to run. In the beginning, I thought there was a error in my program; however, it eventually returned a value.