![]() Note that AMPL still keeps its numbers at full precision, so you need to be careful with your objective function values. To get your solution values to the same number of significant digits. For example, if your inputs are specified to 4 significant digits, e.g., 0.013, you can use You can set the precision for displaying values in AMPL via the display_precision option. It's a powerful tool you won't regret having at your fingertips.When solving mathematical programming problems, the accuracy of your solutions should never be more than theĪccuracy of your data. Take some time to learn printf in your language of choice, and use it when you need it. I don't see any reason printf should be your first choice for printing statements during everyday activities, but it's a great tool to be comfortable enough with that it won't slow you down when you need it. However, if you use printf every now and again, you'll get used to the syntax, and it will become second nature. This is the reason shortcuts like echo and cout were developed. Using printfĪs you can tell from these printf examples, including control characters, especially \n, can be tedious, and the syntax is relatively complex. Notice that a maximum of 3 places are used in each number. Here's an example in Bash for brevity: $ printf "d.jpg\n" When writing to a file programmatically, you can use printf to form the file name with leading zero characters. For instance, if you have 10 sequential files on a computer, the computer may sort 10.jpg before 1.jpg, which is probably not your intent. You can have printf add commas as needed by placing an apostrophe ( ') between the percent sign and the d: $ printf "%'d\n" 1024Īnother common use for printf is to impose a specific format upon numbers in file names. Since big numbers can be difficult to parse, it's common to break them up with a comma. Suppose you want to update your output based on an ever-increasing number: #include įprintf(stdout, "%.2f\n", 4 * atan(1.0)) įor three decimal places, use. It gets even more interesting, though, when the content of a variable changes. This, wrapped in appropriate boilerplate code and executed, renders: $. ![]() Where these values are provided depends on the language you're using and its syntax, but here's a simple example in Java: string var="hello\n" These are placeholders in a printf statement, which you can replace with a value you provide somewhere else in your printf statement. Format output with printfįormat specifiers are characters preceded by a percent sign ( %). The true power of printf lies in format specification. These examples contain nothing more than literal characters, though, and while they're useful in some situations, they're probably the least significant thing about printf. Obviously, Python's print incorporates traditional printf features as well as the features of a simple echo or cout. Using Python's print function for the same task reveals there's more to Python's print command than you might expect: > print("\t\123\n") This is terminated with the control sequence to produce a new line ( \n).Īttempting the same thing with echo produces something a little more literal: $ echo "\t\123\105\124\110\n" In this Bash example, printf renders a tab character followed by the ASCII characters assigned to a string of four octal values.
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