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+.. highlight:: cpp
+
+.. _lang-assert:
+
+``ASSERT(...)``
+===============
+
+ASSERT() can be very useful for basic program debugging. It accepts a
+boolean; for example::
+
+  ASSERT(state == WAIT);
+
+Zero is false and any other number is true.  If the boolean is true,
+the assertion passes and the program continues as usual.  If it is
+false, the assertion fails: the program is halted, debug information
+is printed to USART2, and the status LED begins to throb (it's
+noticeably different from blinking). The debug information is printed
+at 9600 baud and consists of the filename and line number where the
+ASSERT() failed.
+
+Including assertions in a program increases the program size. When
+using libmaple **from the command line only**, they can be disabled by
+making the definition ::
+
+  #define DEBUG_LEVEL DEBUG_NONE
+
+before including either wirish.h or libmaple.h. In this case, all
+assertions will pass without any lost clock cycles.  Note that this
+will **not work in the IDE**; even with this definition, assertions
+will still be enabled.