Maple Language Reference

The Maple can be programmed in the Wiring language, which is the same language used to program the Arduino boards.

C or C++ programmers may wish to skip to the Note for C/C++ Hackers or the Unix Toolchain Quickstart.

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Maple Language Reference

This table is a summary of the most important language features. See the Complete Language Index for a complete listing.

Structure Variables Functions

Control Structures

Further syntax

Arithmetic Operators

  • = (assignment)
  • + (addition)
  • - (subtraction)
  • * (multiplication)
  • / (division)
  • % (modulo)

Comparison Operators

  • == (equal to)
  • != (not equal to)
  • < (less than)
  • > (greater than)
  • <= (less than or equal to)
  • >= (greater than or equal to)

Boolean Operators

  • && (and)
  • || (or)
  • ! (not)

Pointer Operators

Bitwise Operators

  • & (bitwise and)
  • | (bitwise or)
  • ^ (bitwise xor)
  • ~ (bitwise not)
  • << (shift left)
  • >> (shift right)

Compound Operators

  • ++ (increment)
  • - - (decrement)
  • += (compound add)
  • -= (compound subtract)
  • *= (compound multiply)
  • /= (compound divide)
  • &= (compound bitwise and)
  • |= (compound bitwise or)

Keywords

Constants

Data Types

The size of each data type, in bytes, is given in parentheses where appropriate.

Note: The word type is (deliberately) not supported.

Conversion

Variable Scope & Qualifiers

Utilities

Digital I/O

Analog I/O

Advanced I/O

  • tone(): TODO
  • noTone(): TODO
  • shiftOut()
  • pulseIn(): TODO

Time

Math

Trigonometry

Random Numbers

Bits and Bytes

External Interrupts

Interrupts

Communication

Missing Arduino Features

analogReference()

It is not possible to implement this function on the Maple hardware. It will be possible on the upcoming Maple Native.

word

Readers familiar with the Arduino environment may notice that the word datatype is missing from the above table’s list of data types. We chose not to provide the word data type on the Maple. If you want a 16-bit unsigned integer, use the uint16 type instead.

While the Maple has 32-bit words, the word size on an Arduino board is only 16 bits, and code that uses the word type is likely to rely on that fact.

By not supporting word, you’ll get a compile error when porting Arduino code to the Maple instead of potentially weird, hard-to-debug runtime behavior.

If you really must have word, you can include the following typedef in your program:

typedef uint16 word;

Unimplemented Arduino Features

The following Wiring/Arduino features are currently unimplemented on the Maple.

C++ for Maple

If you haven’t programmed in C++, or if you just need to jog your memory, you may want to check out our Language Index. It provides some introductory coverage of programming ideas and C++.

Note for C/C++ Hackers

This is a note for programmers comfortable with C or C++ who want a better understanding of the differences between C++ and the Wiring language.

The good news is that the differences are relatively few; Wiring is just a thin wrapper around C++. Some potentially better news is that the Maple can be programmed using a standard Unix toolchain, so if you’d rather stick with gcc, make, and friends, you can. If you’re using the Unix toolchain and want to skip past the Wiring conveniences and get straight to registers, you are encouraged to move on to the libmaple documentation.

A sketch is the IDE’s notion of a project; it consists of one or more files written in the Wiring language, which is mostly the same as C++. The major difference between the two is that in Wiring, it’s not necessary to declare global functions before they are used. That is, the following is valid Wiring, and f() returns 5:

int f() {
  return g();
}

int g() {
  return 5;
}

All of the files in a sketch share the same (global) namespace. That is, the behavior is as if all of a sketch’s files were part of the same translation unit, so they don’t have to include one another in order to access each other’s definitions. The only other major difference between Wiring and C++ is that Wiring doesn’t support dynamically allocated memory – that is, new and delete won’t work. As of May 16, 2012, Maple only has 20 KB RAM, anyway, so it’s doubtful that static allocation is not what you want.

The Wiring language also does not require you to define your own main method (in fact, we currently forbid you from doing so). Instead, you are required to define two functions, setup and loop, with type signatures

void setup(void);
void loop(void);

Once a sketch is uploaded to a Maple and begins to run, setup() is called once, and then loop() is called repeatedly. The IDE compilation process proceeds via a source-to-source translation from the files in a sketch to C++.

This translation process first concatenates the sketch files, then parses the result to produce a list of all functions defined in the global scope. (We borrow this stage from the Arduino IDE, which in turn borrows it from Wiring. It uses regular expressions to parse C++, which is, of course, Bad and Wrong. In the future, we’ll do this correctly, using a better parser. Until then, you have our apologies.) The order in which the individual sketch files are concatenated is not defined; it is unwise to write code that depends on a particular ordering.

The concatenated sketch files are then appended onto a file which includes WProgram.h (which includes the wirish and libmaple libraries, and declares setup() and loop()), and then provides declarations for all the function definitions found in the previous step. At this point, we have a file that is a valid C++ translation unit, but lacks main(). The final step of compilation provides main(), which behaves roughly like:

int main(void) {
  // Call libmaple's built-in initialization routines
  init();

  // Perform the user's initialization
  setup();

  // Call user loop() forever.
  while (true) {
      loop();
  }
}

(The truth is a little bit more complicated, but not by much).

As an example, consider a sketch with two files. The first file contains setup() and loop():

int the_pin;

void setup() {
  the_pin = choose_a_pin();
  pinMode(the_pin, OUTPUT);
}

void loop() {
  togglePin(the_pin);
}

The second file contains the (not very useful) implementation for choose_a_pin():

int choose_a_pin() {
   return random(5, 15);
}

Then the results of the concatenation process might be

int the_pin;

void setup() {
  the_pin = choose_a_pin();
  pinMode(the_pin, OUTPUT);
}

void loop() {
  togglePin(the_pin);
}

int choose_a_pin(void);

int choose_a_pin() {
   return random(5, 15);
}

Which could plausibly be turned into the final source file

#include "WProgram.h"

void setup(void);
void loop(void);
int choose_a_pin(void);

int the_pin;

void setup() {
  the_pin = choose_a_pin();
  pinMode(the_pin, OUTPUT);
}

void loop() {
  togglePin(the_pin);
}

int choose_a_pin(void);

int choose_a_pin() {
   return random(5, 15);
}

int main() {
  init();
  setup();
  while (true) loop();
}