Yoda Conditions

Yoda Conditions (also: Yoda notation ) denote the programming jargon a form of source code formatting, with the condition within a two parts of the expression are reversed. The name for this programming style is derived from the character Yoda from the Star Wars universe from which tended to exchange a few words within a sentence.

Example

Usually, programmers write a condition in this case, a conditional statement like this:

If ( value == 52) {/ * ... * /} / / Reads like: If the value is equal to 52 .. Yoda Conditions now denote the reverse position of the expression of content:

If ( value == 52 ) {/ * ... * /} / / Reads like: If 52 equal value ... Thus, the constants in this programming style listed first, then the variable comparison value. Analogous to the pronunciation of the name giver Yoda ( " Forget what you have learned earlier you " ) this leads to a strange-looking discussion of the condition: "If zero is equal worth ... ".

Advantage

The interchanging the two conditional values ​​does not change the behavior of the program. Although read worse for the programmer this condition can be considered the first example, this application has in those programming languages ​​that allow assigning a value using " =" in an expression, the advantage of the careless, to make the condition a variable assignment excluded:

If ( value = 52 ) {/ * ... * /} / / If ( unintentionally by the programmer ) always true   if ( value = 52 ) {/ * ... * /} / / Creates a syntax error The example below prevents careless mistakes, as is output or generate an error at run time or at compile time: 52 is a constant; this value can not be assigned.

In some languages ​​can thus also the invalid dereference a null value to be avoided:

String value = null; if ( wert.equals ( " foobar " )) {/ * ... * /} / / In Java here a NullPointerException is thrown   if ( " foobar ". equals ( value) ) {/ * ... * /} / / If (as expected) always wrong criticism

Critics of the notation style to see the lack of readability as a predominant disadvantage of not outweigh the supposed problem of Flüchtigkeitsfehlers described above. It is argued that modern development environments and mark this line as a possible error. Modern programming languages ​​such as C # also does not allow a variable assignment within a condition anyway. In the D programming assignments have no Boolean data type and can not therefore be used as an if - criterion.