title: c++ compile error building arduino project: variable not declared in this scope
body: <p>I'm trying to build someone else's c++ project-- I'm using the code from <a href="https://github.com/SynthesiaSource/Synthesia_Orion_2ndGen" rel="nofollow">here</a>. It's a release of the project, so I believe it's supposed to work as is. However, on compiling I get this error. I've tried moving __gammaTable into the gamma() function, but am not really sure why this isn't considered in its scope.</p>
  
  <pre><code>src/gamma.cpp:15:9: error: 'prog_uchar' does not name a type
   PROGMEM prog_uchar __gammaTable[]  = {
           ^
  In file included from /usr/share/arduino/hardware/arduino/cores/arduino/Arduino.h:8:0,
                   from src/gamma.h:4,
                   from src/gamma.cpp:13:
  src/gamma.cpp: In function 'byte gamma(byte)':
  src/gamma.cpp:42:27: error: '__gammaTable' was not declared in this scope
       return pgm_read_byte(&amp;__gammaTable[x*2 + 2]);
                             ^
  .build/lilypad328/Makefile:339: recipe for target '.build/lilypad328/src/gamma.o' failed
  make: *** [.build/lilypad328/src/gamma.o] Error 1
  Make failed with code 2
  </code></pre>
  
  <p>And here's code tripping the error:</p>
  
  <pre><code>#include "gamma.h"
  
  PROGMEM prog_uchar __gammaTable[]  = {
      0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
      0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  1,  1,  1,  1,
      1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1,  2,  2,  2,  2,
      2,  2,  2,  2,  2,  3,  3,  3,  3,  3,  3,  3,  3,  4,  4,  4,
      4,  4,  4,  4,  5,  5,  5,  5,  5,  6,  6,  6,  6,  6,  7,  7,
      7,  7,  7,  8,  8,  8,  8,  9,  9,  9,  9, 10, 10, 10, 10, 11,
     11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15, 16, 16,
     16, 17, 17, 17, 18, 18, 18, 19, 19, 20, 20, 21, 21, 21, 22, 22,
     23, 23, 24, 24, 24, 25, 25, 26, 26, 27, 27, 28, 28, 29, 29, 30,
     30, 31, 32, 32, 33, 33, 34, 34, 35, 35, 36, 37, 37, 38, 38, 39,
     40, 40, 41, 41, 42, 43, 43, 44, 45, 45, 46, 47, 47, 48, 49, 50,
     50, 51, 52, 52, 53, 54, 55, 55, 56, 57, 58, 58, 59, 60, 61, 62,
     62, 63, 64, 65, 66, 67, 67, 68, 69, 70, 71, 72, 73, 74, 74, 75,
     76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91,
     92, 93, 94, 95, 96, 97, 98, 99,100,101,102,104,105,106,107,108,
    109,110,111,113,114,115,116,117,118,120,121,122,123,125,126,127
  };
  
  byte gamma(byte x) {
      return pgm_read_byte(&amp;__gammaTable[x*2 + 2]);
  }
  </code></pre>