33.9 Translation of Characters

A translation table specifies a mapping of characters into characters. These tables are used in encoding and decoding, and for other purposes. Some coding systems specify their own particular translation tables; there are also default translation tables which apply to all other coding systems.

Function: make-translation-table &rest translations

This function returns a translation table based on the argument translations. Each element of translations should be a list of elements of the form (from . to); this says to translate the character from into to.

The arguments and the forms in each argument are processed in order, and if a previous form already translates to to some other character, say to-alt, from is also translated to to-alt.

You can also map one whole character set into another character set with the same dimension. To do this, you specify a generic character (which designates a character set) for from (see section 33.7 Splitting Characters). In this case, to should also be a generic character, for another character set of the same dimension. Then the translation table translates each character of from's character set into the corresponding character of to's character set.

In decoding, the translation table's translations are applied to the characters that result from ordinary decoding. If a coding system has property character-translation-table-for-decode, that specifies the translation table to use. Otherwise, if standard-translation-table-for-decode is non-nil, decoding uses that table.

In encoding, the translation table's translations are applied to the characters in the buffer, and the result of translation is actually encoded. If a coding system has property character-translation-table-for-encode, that specifies the translation table to use. Otherwise the variable standard-translation-table-for-encode specifies the translation table.

Variable: standard-translation-table-for-decode

This is the default translation table for decoding, for coding systems that don't specify any other translation table.

Variable: standard-translation-table-for-encode

This is the default translation table for encoding, for coding systems that don't specify any other translation table.