Graphite

Unit 4: Corresponding class items

Exercises

Discussion

So far the right-hand (output) side of our GDL rules have contained single glyphs. It is also possible to use a multi-glyph class for substititution.

When one glyph is substituted for another, the Graphite engine determines the position of the input glyph within the input class, and uses the corresponding item from the output class in the substitution. For instance, the following two classes define classes of uppercase and lowercase letters:

table(glyph);
  clsUppercase = unicode(65..90);   // A .. Z
  clsLowercase = unicode(97..122);  // a .. z
endtable;

table(sub);
  clsUppercase > clsLowercase;
endtable;

When, say, the uppercase “H” is encountered in the input, the corresponding lowercase “h” is placed into the output. Keep in mind that the order of the items in the classes becomes very significant when this mechanism is being used.

Note that you need to use parenthesis around the members of a class when there are more than one. For instance:

clsConsVoiced = (gB, gD, gG);
clsConsVoiceless = (gP, gT, gK);

Exercise 4a

Write a program to capitalize all text.

Solution

Exercise 4b

Write a program to make all vowels uppercase and all consonants lowercase.

Solution

Exercise 4c

Write a program to create a Greek transliteration of Roman text, using the mappings in the table below. (You may ignore uppercase for this exercise.) Note that the Unicode codepoints are not in strict numerical order, and that there are no mappings for the letters j and v.

Roman letter	Greek letter	Glyph	Unicode (hex)
a	alpha		03B1
b	beta		03B2
c	chi		03C7
d	delta		03B4
e	epsilon		03B5
f	phi		03C6
g	gamma		03B3
h	eta		03B7
i	iota		03B9
k	kappa		03BA
l	lambda		03BB
m	mu		03BC
n	nu		03BD
o	omicron		03BF
p	pi		03C0
q	theta		03B8
r	rho		03C1
s	sigma		03C3
t	tau		03C4
u	upsilon		03C5
w	omega		03C9
x	xi		03BE
y	psi		03C8
z	zeta		03B6

Compile your program against the SIL Galatia Unicode font (SilGalUni20b1.ttf) that is provided with the tutorial materials.

Solution

Footer Links

• SIL International
• Non-Roman Script Initiative
• ScriptSource
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