How often has this happened to you? You’re working on a piece of code, perhaps even a piece of Challenge code, you add a couple of lines, you compile, and you get some bizarre error. Something nothing near where you were editing. Perhaps an "Illegal function definition …" in a routine you weren’t even working on. And then you realize, eventually if you are slow, or immediately if you are less slow, that you added an "if (condition) {" statement and omitted the closing brace. Or some other simple syntax error.

The first required feature is auto-completion of key words and user-defined names. For example, if I have defined variables "loop_index" and "loop_counter", then, after I type enough characters to uniquely identify a variable name (e.g., "loop_i"), my programmer’s assistant should supply the remaining letters "ndex". The automatically supplied characters should be selected so that they are replaced in the event I continue typing. As a highly desirable optional feature, the assistant should offer me an auto-completion key (e.g., the option key, or a menu item with a keyboard equivalent), which, when pressed, offers me a popup menu of possible completions for the word currently being typed, even when the completion is not uniquely identified.

The second required feature is auto-completion of syntactic elements. If I start a conditional by typing "if", my programmer’s assistant should, when prompted by an auto-completion key, complete the conditional by inserting parentheses, braces, and an "else" clause, leaving something like this:

if () {
} else {
}

In this example, the cursor ought to be left between the parentheses, so that I can insert the conditional. You ought to provide some convenient way for me to move the cursor from the conditional (between the parentheses) to the TRUE branch (between the first pair of braces) to the FALSE branch (between the second pair of braces).

You would provide similar auto-completion for while loops, do loops, for loops:

while () {
}

for ( ; ; ) {
}

do {
} while ();

Other required auto-completions include case statements, struct declarations, enum declarations, and function declarations. Additional auto-completion features may be incorporated at your option. Other options (e.g., indentation styles) will also earn extra feature points.