OpenSCAD User Manual/Type Test Functions

is_undef 2019.05 is_undef accepts one parameter. If the parameter is undef, this function returns true. If the parameter is not undef, it returns false. When checking a variable (like `is_undef(a)`), it does the variable lookup silently, meaning that is_undef(a) does not cause `WARNING: Ignoring unknown variable 'a'. ` The alternative is code like this: if(a==undef){ //code goes here } or b = (a==undef) ? true : false; causes WARNING: Ignoring unknown variable 'a'. is_undef also works for special variables, allowing for things like this: exploded = is_undef($exploded) ? 0 : $exploded; // 1 for exploded view legacy support For older openscad version, is_undef can be emulated with function is_undef ( a ) = (undef == a) ; which of-course causes warning(s), but requires no changes to code relying on is_undef(). is_list 2019.05 echo("returning true"); echo(is_list([])); echo(is_list([1])); echo(is_list([1,2])); echo(is_list([true])); echo(is_list([1,2,[5,6],"test"])); echo("--------"); echo("returning false"); echo(is_list(1)); echo(is_list(1/0)); echo(is_list(((1/0)/(1/0)))); echo(is_list("test")); echo(is_list(true)); echo(is_list(false)); echo("--------"); echo("causing warnings:"); echo(is_list()); echo(is_list(1,2)); is_num 2019.05 echo("a number is a number:"); echo(is_num(0.1)); echo(is_num(1)); echo(is_num(10)); echo("inf is a number:"); echo(is_num(+1/0)); //+inf echo(is_num(-1/0)); //-inf echo("nan is not a number:"); echo(is_num(0/0)); //nan echo(is_num((1/0)/(1/0))); //nan echo("resulting in false:"); echo(is_num([])); echo(is_num([1])); echo(is_num("test")); echo(is_num(false)); echo(is_num(undef)); is_bool 2019.05 echo("resulting in true:"); echo(is_bool(true)); echo(is_bool(false)); echo("resulting in false:"); echo(is_bool([])); echo(is_bool([1])); echo(is_bool("test")); echo(is_bool(0.1)); echo(is_bool(1)); echo(is_bool(10)); echo(is_bool(0/0)); //nan echo(is_bool((1/0)/(1/0))); //nan echo(is_bool(1/0)); //inf echo(is_bool(-1/0)); //-inf echo(is_bool(undef)); is_string 2019.05 echo("resulting in true:"); echo(is_string("")); echo(is_string("test")); echo("resulting in false:"); echo(is_string(0.1)); echo(is_string(1)); echo(is_string(10)); echo(is_string([])); echo(is_string([1])); echo(is_string(false)); echo(is_string(0/0)); //nan echo(is_string((1/0)/(1/0))); //nan echo(is_string(1/0)); //inf echo(is_string(-1/0)); //-inf echo(is_string(undef)); is_function 2021.01 The is_function check works only for expressions, so it can be applied to function literals or variables containing functions. It does not work with built-in functions or normal function definitions. echo(is_function(function(x) x*x)); // ECHO: true func = function(x) x+x; echo(is_function(func)); // ECHO: true function f(x) = x; echo(is_function(f)); // WARNING: Ignoring unknown variable 'f' / ECHO: false is_object Development snapshot Returns true if the argument is an object, and false otherwise.