BRLTTY can display in-line contracted braille. It does this if:
The following contraction tables are provided:
Chinese
Remove excessive white-space.
Grade 2 American English.
Contracted Unified French.
Uncontracted Unified French.
Blank lines are ignored.
Any leading and trailing white-space (any number of blanks and/or tabs) is ignored.
Lines which begin with a number sign (#
) are ignored,
i.e. they're comments.
# This is a comment.
All other lines define table entries.
The general form of a table entry is an opcode followed by its operands. The opcode and its operands are separated from one another by white-space. Each opcode has a specific number of operands, and any text following its last operand is treated as a comment.
opcode operand ... comment
The following operand types are supported:
A sequence of characters other than
white-space (which terminates the string)
and backslashes (\
).
The following special representations are also supported:
\\
backslash
\f
form feed
\n
new line
\o
ooo3-digit octal value
\r
carriage return
\s
blank (space)
\t
horizontal tab
\v
vertical tab
\x
xx2-digit hexadecimal value
An integer. It may be specified in any of the following ways:
A sequence of decimal digits (0
-9
),
with the first digit being nonzero (1
-9
).
A sequence of hexadecimal digits (0
-9
, and either a
-f
or A
-F
),
preceded by either 0x
or 0X
.
A sequence of octal digits (0
-7
),
with the first digit being zero (0
).
A braille symbol.
The braille dots must be specified via their standard numbers
(see section
Standard Braille Dot Numbering Convention),
and, for a multi-cell symbol, the cell specifications
must be separated from one another by a dash (-
).
For example, the contraction for the English word lord
(the letter l
prefixed with dot 5)
would be specified as 5-123
.
A space may be specified via the special dot number 0
.
An opcode is a keyword which tells the translator how to interpret the operands. The opcodes are grouped here by function.
These opcodes make it easier to write contraction tables. They have no direct effect on the character translation.
include
path
Include the contents of another file. Nesting can be to any depth. Relative paths are anchored at the directory of the including file.
locale
locale
Define the locale for character interpretation (lowercase, uppercase, numeric, etc.). The locale may be specified as:
_
country][.
charset][@
modifier]The language component is required and should be a two-letter ISO-639
language code.
The country component is optional and should be a two-letter ISO-3166
country code.
The charset component is optional and should be a character set name, e.g. ISO-8859-1
.
7-bit ASCII.
No locale.
C
locale is assumed.
These opcodes define special symbols which must be inserted into the braille text in order to clarify it.
capsign
dots
The symbol which capitalizes a single letter.
begcaps
dots
The symbol which begins a block of capital letters within a word.
endcaps
dots
The symbol which ends a block of capital letters within a word.
letsign
dots
The symbol which marks a letter which isn't part of a word.
numsign
dots
The symbol which marks the beginning of a number.
These opcodes define the braille representations for character sequences. Each of them defines an entry within the contraction table. These entries may be defined in any order except, as noted below, when they define alternate representations for the same character sequence.
Each of these opcodes has a characters operand (which must be specified as a string), and a built-in condition governing its eligibility for use. The text is processed strictly from left to right, character by character, with the most eligible entry for each position being used. If there's more than one eligible entry for a given position, then the one with the longest character string is used. If there's more than one eligible entry for the same character string, then the one defined nearest to the beginning of the table is used (this is the only order dependency).
Many of these opcodes have a dots operand
which defines the braille representation for its characters operand.
It may also be specified as an equals sign (=
),
in which case it means one of two things.
If the entry is for a single character,
then it means that the currently selected computer braille representation
(see the
-t command line option
and the
text-table configuration file directive)
for that character is to be used.
If it's for a multi-character sequence,
then the default representation for each character
(see
always)
within the sequence is to be used.
Some special terms are used within the descriptions of these opcodes.
A maximal sequence of one or more consecutive letters.
Now, finally, here are the opcode descriptions themselves:
literal
characters
Translate the entire white-space-bounded containing character sequence into computer braille (see the -t command line option and the text-table configuration file directive).
replace
characters characters
Replace the first set of characters, no matter where they appear, with the second. The replaced characters aren't reprocessed.
always
characters dots
Translate the characters no matter where they appear. If there's only one character, then, in addition, define the default representation for that character.
repeated
characters dots
Translate the characters no matter where they appear. Ignore any consecutive repetitions of the same sequence.
largesign
characters dots
Translate the characters no matter where they appear. Remove white-space between consecutive words matched by this opcode.
lastlargesign
characters dots
Translate the characters no matter where they appear. Remove preceding white-space if the previous word was matched by the largesign opcode.
word
characters dots
Translate the characters if they're a word.
joinword
characters dots
Translate the characters if they're a word. Remove the following white-space if the first character after it is a letter.
lowword
characters dots
Translate the characters if they're a white-space-bounded word.
contraction
characters
Prefix the characters with a letter sign (see letsign) if they're a word.
sufword
characters dots
Translate the characters if they're either a word or at the beginning of a word.
prfword
characters dots
Translate the characters if they're either a word or at the end of a word.
begword
characters dots
Translate the characters if they're at the beginning of a word.
begmidword
characters dots
Translate the characters if they're either at the beginning or in the middle of a word.
midword
characters dots
Translate the characters if they're in the middle of a word.
midendword
characters dots
Translate the characters if they're either in the middle or at the end of a word.
endword
characters dots
Translate the characters if they're at the end of a word.
prepunc
characters dots
Translate the characters if they're part of punctuation at the beginning of a word.
postpunc
characters dots
Translate the characters if they're part of punctuation at the end of a word.
begnum
characters dots
Translate the characters if they're at the beginning of a number.
midnum
characters dots
Translate the characters if they're in the middle of a number.
endnum
characters dots
Translate the characters if they're at the end of a number.
These opcodes define and use character classes. A character class associates a set of characters with a name. The name then refers to any character within the class. A character may belong to more than one class.
The following character classes are automatically predefined basdd on the selected locale:
Numeric characters.
Both uppercase and lowercase alphabetic characters. Some locales have additional letters which are neither uppercase nor lowercase.
Lowercase alphabetic characters.
Printable characters which are neither white-space nor alphanumeric.
White-space characters. In the default locale these are: space, horizontal tab, vertical tab, carriage return, new line, form feed.
Uppercase alphabetic characters.
The opcodes which define and use character classes are:
class
name characters
Define a new character class. The characters operand must be specified as a string. A character class may not be used until it's been defined.
after
class opcode ...
The specified opcode is further constrained in that the matched character sequence must be immediately preceded by a character belonging to the specified class. If this opcode is used more than once on the same line then the union of the characters in all the classes is used.
before
class opcode ...
The specified opcode is further constrained in that the matched character sequence must be immediately followed by a character belonging to the specified class. If this opcode is used more than once on the same line then the union of the characters in all the classes is used.