### CSS example with multiple Graphite font features

Source: https://graphite.sil.org/graphite_firefox.html

Shows how to specify multiple Graphite font features using a comma delimiter. Includes both new and old syntax.

```css
.alternate_font_style {
  font-family: "My Graphite Font", <other fallback fonts>;
  /* new syntax: */
  -moz-font-feature-settings: "fea1" 2, "fea2" 6, "fea3"; /* fea3 is 1 or 'on' */
  /* old syntax: */
  -moz-font-feature-settings: "fea1=2,fea2=6,fea3";
}
```

--------------------------------

### Graphite rule with context example

Source: https://graphite.sil.org/tutorial/graide_tutorial6

Example rule that replaces A with X, B with Y, and C with Z, but only fires when the context 'P A Q B C R' is present. The underscores in the context correspond one-to-one with the items on the left- and right-hand sides.

```graphite
gA  gB  gC  >  gX  gY  gZ  /  gP  _  gQ  _  _  gR;
```

--------------------------------

### Graphite rule example

Source: https://graphite.sil.org/tutorial/graide_tutorial1

A simple Graphite rule that maps lowercase letters to uppercase, used in the tutorial's font.

```text
clsLowerCase > clsUpperCase;
```

--------------------------------

### codepoint function examples

Source: https://graphite.sil.org/tutorial/graide_tutorial3

Uses the codepoint function with a string or a numeric value. The optional second argument specifies the codepage; 1252 is the default.

```GDL
codepoint(“a”);
codepoint(97, 1252);
```

--------------------------------

### General GDL table syntax

Source: https://graphite.sil.org/tutorial/graide_tutorial2

Shows the structure for defining a rule table. Replace <table-name> with lb, sub, or pos. Substitution rules like the example go in the sub table.

```GDL
table(<table-name>)
  <rules in the table>
endtable;

```

--------------------------------

### Example CSS style using Graphite font feature 'alts'

Source: https://graphite.sil.org/graphite_firefox.html

Defines a CSS style using a Graphite font with the feature 'alts' set to value 2. Includes both new and old syntax for compatibility.

```css
.alternate_font_style {
  font-family: "My Graphite Font", <other fallback fonts>;
  /* new syntax: */
  -moz-font-feature-settings: "alts" 2;
  /* old syntax: */
  -moz-font-feature-settings: "alts=2";
}
```

--------------------------------

### Run Graide with configuration file

Source: https://graphite.sil.org/tutorial/graide_tutorial1

Use the -p option to start Graide with a specific configuration file, useful for automating project setup.

```text
graide -p tutorial.cfg
```

--------------------------------

### Exercise 5b: Insert u after q/Q with @ syntax alternative

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Exercise 5b: defines a class for q/Q and a glyph for u, then inserts u after any q/Q. The commented line shows an alternative using @1 to copy the item unchanged.

```gdl
#include "stddef.gdh"

table(glyph)
  clsQ = (unicode(0x71), unicode(0x51));
  gU = unicode(0x75);
endtable;

table(sub)
  clsQ  _  >  clsQ  gU:1;

  // Note: you can also use the @ syntax to copy an item through unchanged:
  // clsQ  _  >  @1  gU:1;
endtable;

```

--------------------------------

### Exercise 4a: uppercase mapping via class ranges

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines lower and upper letter classes for 0x61..0x7A and 0x41..0x5A, then maps the lowercase class to the uppercase class.

```gdl
#include "stddef.gdh"

table(glyph)
  clsLower = unicode(0x61..0x7A);
  clsUpper = unicode(0x41..0x5A);
endtable;

table(sub)
  clsLower > clsUpper;
endtable;

```

--------------------------------

### Exercise 13c: Greek Transliteration Feature (r2gk)

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Sets up a 'r2gk' Greek transliteration feature. The glyph table is commented as 'same as previous', and the substitution table contains a placeholder comment for rules to be added.

```GDL
#include "stddef.gdh"

table(glyph)
  // same as previous
endtable;

table(feature)

greek_xlit {
  id = "r2gk"
  name.LG_USENG = string("Greek Transliteration");
}

endtable;

table(sub)

if (greek_xlit)
  // rules go here
endif;

endtable;

```

--------------------------------

### Original class definition with codepoint

Source: https://graphite.sil.org/tutorial/graide_tutorial1

The original class definition for uppercase letters, which is highlighted in the editor. This line is used as a starting point for introducing errors.

```gdl
clsUpperCase = codepoint(“ABCDEFGHIJKLMNOPQRSTUVWXYZ”);

```

--------------------------------

### Exercise 3a: map glyphs using gDollar and gPound

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines a glyph table with the named glyphs gDollar and gPound, then a substitution table that maps gDollar to gPound.

```gdl
#include "stddef.gdh"

table(glyph)
  gDollar = unicode(0x0024);
  gPound = unicode(0x00A3);
endtable;

table(sub)
  gDollar > gPound;
endtable;

```

--------------------------------

### Exercise 14c: Tone glyph classes and substitution rules

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines glyph classes for numbers (one, two, thr) and tone combinations (two-tone and three-tone). Substitution rules match sequences of numbers and replace them with tone ligatures, assigning component references (@1, @2, @3) for tone1, tone2, and tone3. The rules cover two-tone (low2, mid2, high2) and three-tone (lowLow3, lowMid3, etc.) combinations, each with component boxes for positioning tones.

```Graphite GDL
#include "stddef.gdh"

table(glyph)
  one = U+0031;    // 1
  two = U+0032;    // 2
  thr = U+0033;    // 3

  clsNumber = (one, two, thr);

  oneTone = (glyphid(381), glyphid(368), glyphid(354));

  // Two-tone combinations:

  low2 =  (glyphid(381), glyphid(382), glyphid(383));
  mid2 =  (glyphid(367), glyphid(368), glyphid(369));
  high2 = (glyphid(352), glyphid(353), glyphid(354));

  twoTone = (low2, mid2, high2)
    { comp { tone1 = box(0, -descent, aw/2, ascent);
             tone2 = box(aw/2, -descent, aw, ascent) } };
                 
  // Three-tone combinations:
  lowLow3 =   (glyphid(381), glyphid(391), glyphid(392));
  lowMid3 =   (glyphid(446), glyphid(447), glyphid(383));
  lowHigh3 =  (glyphid(450), glyphid(451), glyphid(452));
  midLow3 =   (glyphid(376), glyphid(377), glyphid(378));
  midMid3 =   (glyphid(433), glyphid(368), glyphid(434));
  midHigh3 =  (glyphid(437), glyphid(438), glyphid(439));
  highLow3 =  (glyphid(362), glyphid(363), glyphid(364));
  highMid3 =  (glyphid(352), glyphid(420), glyphid(421));
  highHigh3 = (glyphid(424), glyphid(425), glyphid(354));

  threeTone = (lowLow3,  lowMid3,  lowHigh3,
               midLow3,  midMid3,  midHigh3,
               highLow3, highMid3, highHigh3)
    { comp{ tone1 = box(0, -descent, aw/3, ascent);
            tone2 = box(aw/3, -descent, aw * 2/3, ascent);
            tone3 = box(aw * 2/3, -descent, aw, ascent) } };
endtable;

table(sub)
  // Three-tone sequences:

  one  one  clsNumber  >  _  _  lowLow3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};
  one  two  clsNumber  >  _  _  lowMid3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};
  one  thr  clsNumber  >  _  _  lowHigh3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};

  two  one  clsNumber  >  _  _  midLow3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};
  two  two  clsNumber  >  _  _  midMid3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};
  two  thr  clsNumber  >  _  _  midHigh3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};

  thr  one  clsNumber  >  _  _  highLow3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};
  thr  two  clsNumber  >  _  _  highMid3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};
  thr  thr  clsNumber  >  _  _  highHigh3:(1 2 3)
    {comp { tone1.ref = @1; tone2.ref = @2; tone3.ref = @3 }}};

  // Two-tone sequences:

  one  clsNumber  >  _  _  low2:(1 2)
    {comp { tone1.ref = @1; tone2.ref = @2 }}};
  two  clsNumber  >  _  _  mid2:(1 2)
    {comp { tone1.ref = @1; tone2.ref = @2 }}};
  thr  clsNumber  >  _  _  high2:(1 2)
    {comp { tone1.ref = @1; tone2.ref = @2 }}};

  // Single tones:

  clsNumber  >  _  _  oneTone;

endtable;

```

--------------------------------

### Enable bidi pass with Bidi = true;

Source: https://graphite.sil.org/tutorial/graide_tutorial15

Turns on the bidi pass in a Graphite font. Place this statement in the font's GDL code to enable bidirectional reordering.

```gdl
Bidi = true;

```

--------------------------------

### GDL: Defining a user-defined slot attribute with #define

Source: https://graphite.sil.org/tutorial/graide_tutorial9

Shows how to define a user-defined slot attribute using the #define directive. This example defines 'hardC' as 'user1', making it number 1 in the list of user attributes.

```gdl
#define hardC user1

```

--------------------------------

### Exercise 14b: Fraction glyph classes and substitution rules

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines glyph classes for digits 1, 3, 4, slash, and fraction ligatures (1/4, 1/2, 3/4). Each fraction component (num, slash, denom) is positioned using box() with coordinates relative to the bounding box. Substitution rules match a numerator, slash, and denominator and replace them with the corresponding ligature, assigning component references (@1, @2, @3).

```Graphite GDL
#include "stddef.gdh"

table(glyph)
  gNum1 = unicode(0x31);  // 1
  gNum3 = unicode(0x33);  // 3
  clsDenom1 = (unicode(0x34), unicode(0x32));  // 4,2
  clsDenom3 = unicode(0x34); // 4
  gSlash = unicode(0x2f);
  clsLig1 = (unicode(0xbc), unicode(0xbd));  // 1/4, 1/2
  clsLig3 = unicode(0xbe);  // 3/4

  // Each component is half the width of the bounding box:
  clsLig = unicode(0xbc..0xbe)    // 1/4, 1/2, 3/4
    { comp.num = box(bb.left, bb.bottom + 200m, lsb + bb.width*3/8, bb.top);
      comp.slash = box(lsb + bb.width/3, bb.bottom, (lsb + bb.width*2/3, bb.top) ;
      comp.denom = box(lsb + bb.width*5/8,  bb.bottom – 100m, bb.right, bb.bottom + 600m)
    };
endtable;

table(sub)
  // 1/4, 1/2
  gNum1 gSlash clsDenom1  >
      _  _  clsLig1:(1 2 3) {
              comp {num.ref = @1; slash.ref = @2; denom.ref = @3}}};
  // 3/4
  gNum3 gSlash clsDenom3  >
      _  _  clsLig3:(1 2 3) {
              comp {num.ref = @1; slash.ref = @2; denom.ref = @3}}};
endtable;

```

--------------------------------

### Exercise 4b: vowel and consonant class mappings

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines lowercase and uppercase vowel classes (a e i o u) and consonant classes, then maps lowercase vowels to uppercase vowels and uppercase consonants to lowercase consonants in one substitution table.

```gdl
#include "stddef.gdh"

table(glyph)
  clsLowerVowel = (U+0061, U+0065, U+0069, U+006F, U+0075);  // a e i o u
  clsUpperVowel = (U+0041, U+0045, U+0049, U+004F, U+0055);  // A E I O U

  clsLowerCons = ((U+0062..U+0064), // b..d
    (U+0066..U+0068),     // f..h
    (U+006A..U+006E),     // j..n
    (U+0070..U+0074),     // p..t
    (U+0076..U+007A));    // v..z
  clsUpperCons = ((U+0042..U+0044), // B..D
    (U+0046..U+0048),     // F..H
    (U+004A..U+004E),     // J..N
    (U+0050..U+0054),     // P..T
    (U+0056..U+005A));    // V..Z
endtable;

table(sub)
  clsLowerVowel > clsUpperVowel;
  clsUpperCons > clsLowerCons;
endtable;

```

--------------------------------

### Graide test data: Unicode codepoint syntax

Source: https://graphite.sil.org/tutorial/graide_tutorial11

Syntax for entering non-ASCII characters in Graide test data using Unicode codepoints. Replace <USV> with the Unicode scalar value. For example, X\u0308 enters X with diaeresis.

```text
\u<USV>
```

--------------------------------

### Exercise 14a: Ligature Feature with Component Composition (ligs)

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Untested solution for a ligature feature. Defines ligature components (off, eil, and ligature glyphs) and a substitution rule that composes ligatures from two components using comp.c1 and comp.c2 references. Note the warning that this solution has not been tested.

```GDL
#include "stddef.gdh"

table(glyph)
  clsLigComp1 =
    (unicode(0x6f), unicode(0x66), unicode(0x66));  // off
  clsLigComp2 =
    (unicode(0x65), unicode(0x69), unicode(0x6c));  // eil
  // Each component is half the width of the bounding box:
  clsLig = (glyphid(155), // oe
    glyphid(168), // fi
    glyphid(169)) // fl
    {
      comp.c1 = box(bb.left, bb.bottom,    bb.width/2, bb.top);
      comp.c2 = box(bb.width/2, bb.bottom, bb.right, bb.top)
    };

endtable;

table(feature)

lig {
  id = "ligs";
  name.LG_USENG = string("Ligatures");
}

endtable;

table(sub)

if (lig)
  // Note: we use the second character as the selector of
  // the replacement ligature, since it can unambiguously 
  // identify it
  clsLigComp1  clsLigComp2  >
       _  clsLig:(1 2) { comp.c1.ref = @1; comp.c2.ref = @2 };
endif;

endtable;

```

--------------------------------

### Exercise 17: Reordering with context pattern

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Extends Exercise 16 by adding a context pattern to the substitution rule. The rule reorders a consonant and back-rounded vowel, but only when followed by an optional consonant or pair of consonants and an underscore.

```graphite
#include "stddef.gdh"

table(glyph)
  clsBackRoundedVowel = (unicode(0x6f), unicode(0x75));  // o, u
  clsCons = (unicode(0x62..0x64),  // b..d
    unicode(0x66..0x68),           // f..h
    unicode(0x6A..0x6E),           // j..n
    unicode(0x70..0x74)            // p..t
    unicode(0x76..0x7A));          // v..z
endtable;

table(sub)
  _  clsCons  clsBackRoundedVowel  >  @5  @2  _
        / _  _ [clsCons clsCons? ]? _;
endtable;

```

--------------------------------

### Use AttributeOverride and followsHardC to change C based on vowel class (Exercise 7)

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Gramble (GDL) program for Exercise 7. Uses AttributeOverride to override followsHardC for soft vowels (§ Exercise 7).

```gd
#include "stddef.gdh"

// The following is true by default, so does not really need to 
// be stated. It needs to be true because we are overriding
// the value of followsHardC for soft vowels in the glyph table.
environment { AttributeOverride = true };

table(glyph)
  gC = (U+0063 U+0043);
  gK = (U+006b U+004b);
  gS = (U+0073 U+0053);
  clsLetter = ((U+0061..U+007a), (U+0041..U+005a))
            {followsHardC = true};
  clsSoftVowel =
     (U+0065, U+0069, U+0079,  // eiy
      U+0045, U+0049, U+0059)  // EIY
            {followsHardC = false}; // overrides above
endtable;

table(sub)
  gC  >  gK  /  _  clsLetter { followsHardC };
  gC  >  gS  /  _  clsLetter { !followsHardC };
endtable;

endenvironment;

```

--------------------------------

### Exercise 18: Case-sensitive reordering with context

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines separate lower-case and upper-case classes for back-rounded vowels and consonants, then combines them. Substitution rules reorder consonant-vowel pairs with case-specific handling, using context patterns and explicit slot references. The note explains that `clsConsLC$2:2` can be written as `clsConsLC` for clarity.

```graphite
#include "stddef.gdh"
table(glyph)
  clsBackRndVowelLC = (unicode(0x6f), unicode(0x75)); // o, u
  clsBackRndVowelUC = (unicode(0x4f), unicode(0x55)); // O, U
  clsBackRndVowel = (clsBackRndVowelLC clsBackRndVowelUC);

  clsConsLC = (unicode(0x62..0x64),   // b..d
    unicode(0x66..0x68),              // f..h
    unicode(0x6A..0x6E),              // j..n
    unicode(0x70..0x74),              // p..t
    unicode(0x76..0x7A));             // v..z
  clsConsUC = (unicode(0x42..0x44),   // B..D
    unicode(0x46..0x48),              // F..H
    unicode(0x4A..0x4E),              // J..N
    unicode(0x50..0x54),              // P..T
    unicode(0x56..0x5A));             // V..Z
  clsCons = (clsConsLC clsConsUC);
endtable;

table(sub)
  // Move upper-case from consonant to reordered vowel.
  _  clsConsUC  clsBackRndVowelLC  >  clsBackRndVowelUC$5:5  clsConsLC$2:2  _  // see note below
      /  _  _  [clsCons clsCons? ]?  _;

  // Move upper-case from vowel to consonant (odd, but you never know!).
  _  clsConsLC  clsBackRndVowelUC  >  clsBackRndVowelLC$5:5  clsConsUC$2:2
      / _  _  [clsCons clsCons? ]?  _;

  // Otherwise, case matches on vowel and consonant; just reorder.
  _  clsCons clsBackRndVowel  >  @5  @2  _
      / _ _ [clsCons clsCons? ]? _;
endtable;

```

--------------------------------

### Exercise 19a: Define hyphen-like glyph class with intra-word breaks

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines a glyph class 'clsHyphenLike' containing hyphen, equals, underscore, and tilde, and sets their break property to BREAK_INTRA. No additional rules are needed for this exercise.

```graphite
#include "stddef.gdh"
table(glyph)
  clsHyphenLike = (unicode(0x2d), unicode(0x003d), unicode(0x5f), unicode(0x7e))
    { break = BREAK_INTRA };
endtable;

// No rules needed!

```

--------------------------------

### Exercise 5a: Roman-to-Greek substitution with deletion rules

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Exercise 5a: defines glyph classes for Roman and Greek letters, then deletes j and v and maps sequences like t+h to theta. Note: this program generates warnings for the deletion rules, and Linux users have reported compilation errors.

```gdl
#include "stddef.gdh"

table(glyph)

  // Roman

  clsRoman = ((U+0061..U+0069),  // a..i
    (U+006B..U+0075),   // k..u
    (U+0077..U+007a));  // w..z

  gJ = U+006a;
  gV = U+0076;
  gH = U+0068;
  gT = U+0074;
  gP = U+0070;
  gS = U+0073;

  // Greek

  clsGreek = (U+03b1, // alpha
    U+03b2,   // beta
    U+03c7,   // chi
    U+03b4,   // delta
    U+03b5,   // epsilon
    U+03c6,   // phi
    U+03b3,   // gamma
    U+03b7,   // eta
    U+03b9,   // iota
    U+03ba,   // kappa
    U+03BB,   // lambda - use BB to avoid compiler bug
    U+03bc,   // mu
    U+03bd,   // nu
    U+03bf,   // omicron
    U+03d0,   // pi
    U+03b8,   // theta
    U+03c1,   // rho
    U+03c2,   // sigma
    U+03c4,   // tau
    U+03c5,   // upsilon
    U+03c9,   // omega
    U+03be,   // xi
    U+03c8,   // psi
    U+03b6);  // zeta

  gTheta = U+03b8;
  gPhi = U+03c6;
  gPsi = U+03c8;

endtable;

table(sub)
  // Delete j and v. Here we do not associate them
  // with any surface glyph, so it will be impossible
  // to select or manipulate them.
  gJ  >  _;
  gV  >  _;

  // Handle sequences.
  gT gH  >  gTheta:(1 2) _;
  gP gH  >  gPhi:(1 2) _;
  gP gS  >  gPsi:(1 2) _;

  // Everything else:
  clsRoman > clsGreek;
endtable;

```

--------------------------------

### Exercise 12c: Manual attachment points with overrides

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines attachment points for base letters, iota subscript, and breathing marks. Overrides the attachment point for eta (gEta) and uses a negative offset for breathing marks.

```graphite
#include "stddef.gdh"

table(glyph)
  clsBase = (unicode(0x03b1) unicode(0x03b7), unicode(0x03c9))
        { attPtIota = point(lsb + bb.width/2, bb.bottom);
          attPtBreath = point(lsb + bb.width/2, bb.top)
    };
  // Adjust x-position of attachment point for eta. We are in 
  // effect overriding the value set above.
  gEta = unicode(0x03b7)
        { attPtIota = point(lsb + (bb.width*3/8), bb.bottom + 160m) };
  gIotaDiac = unicode(0x0345)
        { attPt = point(lsb + bb.width/2, bb.bottom + 50m) };
  clsBreathDiac = unicode(0x0313..0x0314)
        { attPt = point(lsb + bb.width/2, bb.bottom – 50m) };
endtable;

table(pos)
  clsBase
      clsBreathDiac { attach { to=@1; at=attPtBreath; with=attPt } }
      gIotaDiac { attach { to=@1; at=attPtIota; with=attPt } };

  clsBase  gIotaDiac { attach { to=@1; at= attPtIota; with=attPt } };
endtable;
```

--------------------------------

### Mark C with hardC attribute and substitute in two passes (Exercise 9)

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Gramble (GDL) program for Exercise 9. Defines hardC as user1 and uses two passes: first marks C based on context, then substitutes. (§ Exercise 9)

```gd
#include "stddef.gdh"

#define hardC user1

table(glyph)
  gC = (U+0063 U+0043);
  gK = (U+006b U+004b);
  gS = (U+0073 U+0053);

  clsHardLetter = (
    (U+0061..U+0064), // a..d
    (U+0066..U+0068), // f..h
    (U+006A..U+0078), // j..x
     U+007A,          // z
    (U+0041..U+0044), // A..D
    (U+0046..U+0058), // F..H
    (U+004A..U+0058), // J..X
     U+005A);         // Z
  clsSoftLetter =
    (U+0065, U+0069, U+0079,  // eiy
     U+0045, U+0049, U+0059)  // EIY

endtable;

table(sub)

pass(1)
  // Mark the C based on its context.
  gC {hardC = true}  /  _  clsHardLetter;
  gC {hardC = false}  /  _  clsSoftLetter;
endpass;

pass(2);
  // Make the substitution.
  gC  >  gK  /  _ {hardC};
  gC  >  gS  /  _ {!hardC};
endpass;

endtable;

```

--------------------------------

### Exercise 12b: Manual attachment points for diacritics

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines attachment points lowerM and lowerS for diacritic and base glyph classes, then attaches them in the pos table. Uses a workaround for a hinting bug by setting PointRadius to 0.

```graphite
#include "stddef.gdh"

environment { PointRadius = 0 } // workaround for hinting bug

table(glyph)
  clsDiac = (unicode(0x0316) unicode(0x0317), unicode(0x031f), unicode(0x0327..0x0330))
        { lowerM = point(lsb + bb.width/2, bb.top + 50m) };
  clsBase = (unicode(0x61..0x7a), unicode(0x41..0x5a))
        // An alternative to "advancewidth/2" is lsb + bb.width/2.
        { lowerS = point(advancewidth/2, bb.bottom) };
endtable;

table(pos)
  clsBase  clsDiac { attach { to=@1; at=lowerS; with=lowerM } };
endtable;

endenvironment;
```

--------------------------------

### Include stddef.gdh in GDL file

Source: https://graphite.sil.org/tutorial/graide_tutorial2

Adds standard definitions and abbreviations from the stddef.gdh file. Place at the beginning of the GDL file.

```GDL
#include "stddef.gdh"

```

--------------------------------

### Exercise 2: map $ to £ as table(sub)

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines a substitution table that maps the dollar sign (U+0024) to the pound sign (U+00A3). The source shows a comment indicating the alternative syntax 'U+0024 > U+00A3'.

```gdl
#include "stddef.gdh"

table(sub)
  unicode(0x0024) > unicode(0x00A3);  // or U+0024 > U+00A3
endtable;

```

--------------------------------

### Exercise 3b: map a digit class to an asterisk

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines a glyph class clsDigit for the range U+0030..U+0039 and a glyph gAsterisk, then maps the entire class to the asterisk glyph in a substitution table.

```gdl
#include "stddef.gdh"

table(glyph)
  clsDigit = (U+0030..U+0039);
  gAsterisk = U+002A;
endtable;

table(sub)
  clsDigit > gAsterisk;
endtable;

```

--------------------------------

### Range with codepoint and comment

Source: https://graphite.sil.org/tutorial/graide_tutorial3

Defines a class using a range of codepoint values. Comments are preceded by two slashes.

```GDL
clsLowercase = codepoint(97..122);   // a through z
```

--------------------------------

### GDL rule using U+ codepoint syntax

Source: https://graphite.sil.org/tutorial/graide_tutorial2

Alternative syntax for specifying Unicode codepoints. Does not require '0x' prefix, but the 'U' must be capitalized.

```GDL
U+0061 > U+0062;

```

--------------------------------

### Graphite rule with context syntax

Source: https://graphite.sil.org/tutorial/graide_tutorial6

Shows the general syntax for a Graphite rule with context. The context follows a slash after the right-hand side, and each item from the left- and right-hand sides is represented by an underscore in the context.

```graphite
left-hand-side  >  right-hand-side  /  context;
```

--------------------------------

### Exercise 15: Minimal glyph table with upper-case class

Source: https://graphite.sil.org/tutorial/graphite_tut_solutions

Defines a glyph table with a single class for upper-case letters (U+0041..U+005A) with right direction. The lower-case class is commented out because it is true by default. No rules are needed.

```graphite
#include "stddef.gdh"

Bidi = true;

table(glyph)

  // Not needed; true by default:
  //clsLower = (U+0061..U+007a) { dir = DIR_LEFT };

  clsUpper = (U+0041..U+005a) { dir = DIR_RIGHT };

endtable;

// No rules needed!

```