A student's question

My teacher keeps drilling into our collective heads that using the break command is harmful, and that if we wish to terminate a loop early it would be far better to create a boolean variable, set it to 0, and add a condition to the head of the loop, and set the boolean variable to 1 when a break is needed. Note that this way you actually have to check this every single loop (where it is not needed almost every time) as well as waste a command to reset the boolean in case it was set to true.

Is there a reason to this?

>>23
Macro systems have a range of uses. Being able to choose the order of evaluation (see lazy evaluation and non-strict functions) enables the creation of new syntactic constructs (e.g. control structures) indistinguishable from those built into the language. For instance, in a Lisp dialect that has cond but lacks if, it is possible to define the latter in terms of the former using macros.

Next, macros make it possible to define data languages that are immediately compiled into code, which means that constructs such as state machines can be implemented in a way that is both natural and efficient.[8]

Macros can also be used to introduce new binding constructs. The most well-known example is the transformation of let into the application of a function to a set of arguments.

Felleisen conjectures[9] that these three categories make up the primary legitimate uses of macros in such a system.