The following values in Python are false in the context of if and other logical contexts: False None numeric values equal to 0, such as 0, 0.0, -0.0 empty strings: ” and u” empty containers (such as lists, tuples and dictionaries) anything that implements __bool__ (in Python3) to return False, or __nonzero__ (in Python2) to … Read more
Use the variable substring syntax: IF “%variable:~0,3%”==”ABC” […] If you need the path to the batch file without the batch file name, you can use the variable: %~dp0 Syntax for this is explained in the help for the for command, although this variable syntax extends beyond just the for command syntax.
If you want to check for false and alert if not, then no there isn’t. If you use if(val), then anything that evaluates to ‘truthy’, like a non-empty string, will also pass. So it depends on how stringent your criterion is. Using === and !== is generally considered good practice, to avoid accidentally matching truthy … Read more
You can check if a directory is empty using find, and processing its output: #!/bin/sh target=$1 if find “$target” -mindepth 1 -print -quit 2>/dev/null | grep -q .; then echo “Not empty, do something” else echo “Target ‘$target’ is empty or not a directory” fi That is: Use find to find the first filesystem entry … Read more
Performance The ternary operator shouldn’t differ in performance from a well-written equivalent if/else statement… they may well resolve to the same representation in the Abstract Syntax Tree, undergo the same optimisations etc.. Things you can only do with ? : If you’re initialising a constant or reference, or working out which value to use inside … Read more
In recent versions of AutoMapper, ResolveUsing was removed. Instead, use a new overload of MapFrom: void MapFrom<TResult>(Func<TSource, TDestination, TResult> mappingFunction); Just adding another lambda/function parameter will dispatch to this new overload: CreateMap<TSource, TDest>() .ForMember(dest => dest.SomeDestProp, opt => opt.MapFrom((src, dest) => { TSomeDestProp destinationValue; // mapping logic goes here return destinationValue; }));
No, if (c) is the same as if (c != 0). And if (!c) is the same as if (c == 0).
I would use: if File.readlines(“testfile.txt”).grep(/monitor/).any? or if File.readlines(“testfile.txt”).any?{ |l| l[‘monitor’] } Using readlines has scalability issues though as it reads the entire file into an array. Instead, using foreach will accomplish the same thing without the scalability problem: if File.foreach(“testfile.txt”).grep(/monitor/).any? or if File.foreach(“testfile.txt”).any?{ |l| l[‘monitor’] } See “Why is “slurping” a file not a good … Read more
Yes you can go wild nesting ternaries. I find this version to be fairly readable: var foo = ( bar === ‘a’ ? 1 : // if bar === ‘b’ ? 2 : // else if bar === ‘c’ ? 3 : // else if null // else ); but that’s not a widely shared … Read more