|
|||||
|
|
|||||
| operator | binary | ||||
| Sample Code | Related Syntax | Related Concepts | |||
| Summary |
Numeric
Yields the numeric value of a string sequence. |
string-expression binary numeric-expression OR with binary numeric-expression
binary can be used in several different ways: mathematical operator, prefix operator, or open modifier. Each is described in turn below.
As a mathematical operator, it is used to process a string of 1 to 4 characters as if it were a sequence of 8 to 32 bits, and to yield the number represented by the sequence. This can be very useful when processing binary data in files, where numbers are often stored as bit sequences rather than as string representations.
For example, a word processor that uses escape codes and character counts to indicate the length of a given sequence might specify that the next 90 bytes should be underlined by two characters "%21#%90#. (The "%21#" character is also known as a "Control-U" character, obtained by pressing the CTRL-U on the keyboard. The "%90#" is also the letter "z".) This representation is more succinct than using the character "90" to represent the length.
In OmniMark, converting a value such as "z" into its decimal value (in this example, 90) is done using the binary operator. As long as the string values are one-character long (a zero-length string may not be converted), the order of evaluation is obvious.
A problem arises when a numeric value is represented with more than one byte. On some systems, the higher the byte position, the more significant its value; on others, the lower bytes are more significant. Some other systems only swap bytes within each pair: the higher pair could be more significant, but within each pair the lower byte would be more significant.
The binary operator can be used in two different ways. The general form takes two operands:
The more compact form of binary takes only the string-expression operand. The default ordering is 0. This can be changed with the binary-input declaration.
binary can be used as a prefix operator when the desired byte ordering is the same as:
binary-input declaration.
binary-input.
binary can also be used as an open modifier. In this form, binary is followed by a numeric expression that evaluates to a valid binary ordering number (0, 1, 2, or 3). The binary modifier specifies the default byte ordering code to use in "%b" format items written to that stream. It overrides the default established by the binary-output declaration.
The following list describes the meaning of each byte-ordering value.The example shows how different values affect conversion on the string "%10r{1,2,3,4}".
Code numbers greater than 3 are divided by 4, and the remainder is used (that is the code number "modulo" 4 is used). Code numbers less than zero are in error.
The following example demonstrates the use of the binary operator to convert binary data to a numeric expression:
cross-translate
find any {1 to 4} => word
local counter i
set i to word binary 0
output "The value is %d(i)%n"
|
Sample Code
Binary input conversion |
Related Syntax binary-input open reopen |
Related Concepts Files: binary and text-mode Operators: the precedence of "base" and "binary" |
| ---- |
