$func? IsBox e.Exp = ;
$func? IsChannel e.Exp = ;
$func? IsChar e.Exp = ;
$func? IsDigit e.Exp = ;
$func? IsFunc e.Exp = ;
$func? IsInt e.Exp = ;
$func? IsLetter e.Exp = ;
$func? IsString e.Exp = ;
$func? IsTable e.Exp = ;
$func? IsVector e.Exp = ;
$func? IsWord e.Exp = ;
These functions provides a way to determine whether e.Exp is a symbol
belonging to a certain class of symbol.
If e.Exp is not a single symbol, the functions return
$fail(0).
If e.Exp is a symbol, the test is performed whether the symbol belongs to
the corresponding class of symbols. If so, the value returned is an empty ground expression.
Otherwise, the value returned is $fail(0).
The correspondence between the predicate functions and the sets of symbols is as follows.
IsBox
- references to boxes.
IsChannel
- references to channels.
IsChar
- character symbols.
IsDigit
- character symbols corresponding to decimal digits.
IsFunc
- references to functions.
IsInt
- references to integers.
IsLetter
- character symbols corresponding to small and capital letters.
IsString
- references to strings.
IsTable
- references to tables.
IsVector
- references to vectors.
IsWord
- word symbols.