Before moving off the topic of arrays and their bogus dimensions, I want to play further with a magic square. Specifically, it intrigues me that you can shift rows or columns within the square and it doesn’t affect the magical properties.
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Author Archives: dgookin
Pass a 2D Array to a Function (No Pointers!)
Suppose you have an array of integers which represents a magic square: All the rows and columns — even the two diagonals — add to the same total. To prove it, you create a function, confirm_magic() that processes the array and validates the math. You have just one problem . . .
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A Single-Dimension Array Pretends to be Two-Dimensions
Multi-dimension array notation is just a handy shortcut for you, the human programmer. Internally, an array is a single-file line of values, one marching after another. The dimensional aspect helps humans organize the array’s data, but all that organization is superficial.
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Day-of-the-Year Calculation – Solution
The solution for this month’s Exercise involves two steps. The first is to generate a random value from 1 to 365 (inclusive) as a day-of-the-year value. The second is to determine upon which month and day that value falls. That part may offer more difficulty than you anticipate.
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Two Dimensional Arrays are a Myth
Do C language pointers frighten you? Good! They’re supposed to, mostly because few instructors bother explaining them well, but also because of the nomenclature: “Pointers point.” Regardless, if you shun pointers, as many C programmers do, you can fall back on array notation. It’s a useful alternative and a handy shortcut, but it’s completely bogus.
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Day-of-the-Year Calculation
Today is May 1st. It’s the 121st day of the year 2017. In 2016, May 1 was the 122nd day of the year, because 2016 was a leap year. You can look up this information on a calendar or, more disappointingly, use Google. You can also write code that does the calculation for you, which is this month’s Exercise.
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Structure Size and Memory Alignment
Though it’s possible to guess the byte size of a structure, it’s bad practice to do so. Even advanced C programmers, who know variable widths by heart, rely upon the sizeof operator to obtain a structure’s size.
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Look at the sizeof That Thing
A structure is a multi-variable, containing several variable types, all members of the same unit. Two declarations are required for a structure: The structure itself and the variable. Programmers get into trouble with structures when determining the variable’s size, using typedef as a structure shortcut, and when declaring structure pointers.
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Surrender to the Overflow
It’s a common question beginning programmers ask: “Why use different types of variables when every number can be expressed as a float?”
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The strftime() Function
Being a C nerd, I occasionally browse the C library to discover new functions. Such an exercise is a must, not just for C but for any programming language. That’s because programmers can become complacent and rely upon the same old tricks. Only by reviewing the libraries, or by looking at other programmers’ code, can you learn new things.
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