Alias

An alias gives a name to a value. Wherever the name appears, the value is dropped in its place — the alias itself never reaches the compiled parser.

A character literal and its chains and ranges, a character block, a number and a text literal can all be aliased.

program example;

alias letter <A:Z>;        # character block
alias code \x41;           # character literal
alias bigcode \x41:43;     # range
alias chaincode \x41,42,43,44;  # chain
alias limit 100;           # number
alias animal "CAT";        # text

A = letter;
B = animal;

Where a number alias goes

A number matches nothing, so a number alias is not a unit. It belongs where a number is wanted — a counter bound, a logic block or a variable:

alias width 4;

field = char-width;          # a counter bound
check = {x < width};         # logic
numvar w = width;            # a global's initial value

Writing A = width; is refused, for the same reason writing A = 4; is: neither says anything a parser could match.

Note

An alias is a substitution, not an indirection. alias tab \x09; puts the tab character itself everywhere tab is written, so the parser is exactly the one you would have got by typing the value out.