old‐sl‐sh Reader

Reader

The reader should be more less as expected for a lisp reader.

Strings

String are surrounded by "" and can be multiline. Stings support the following escape sequences:

• \n: newline
• \r: carriage return
• \t: tab
• \: backslash
• \xnn: A two digit hex up to 7F, becomes the 7 bit ascii code provided (which is utf8 compatible)
• \u{nnnn} or \unnnn: Second form must be followed by whitespace, embedd a unicode scalar with the value (in hex) of nnnn up to 4 bytes

String Literals

String literals are started with #"_ and end with ". The _ can be any char and must match on both ends. Anything between the opening #" and _" will be part of the resulting string (nothing is escaped or expanded).

Chars

Chars are read using #\x format (for instance 'S' would be #\S). Char supports the following special cases:

• #\space: space character
• #\tab: tab character
• #\newline: newline
• #\linefeed: linefeed
• #\return: carriage return
• #\backspace: backspace
• #\xnn: the 7 bit ascii code (up to 7F) as two hex digits
• #\u{nnnn} or \unnnn: the unicode scalar with the value (in hex) of nnnn up to 4 bytes

Reader macros

Are supported- add details.

Vectors

Use the #() syntax to create a vector instead of a list (in sl-sh vectors can be evaluated like lists).

Comments

Comment to end of line with the ; character.

Block comment with #|...|# these can be multiline and can be embedded.

Comment out (read and throwaway) s-expression with #;. If the sexp after #; is not readable then it will raise an error. Will call reader macros in order to read the sexp.

Builtin macros under the # key

• #| start block comment
• #\ character
• #< unreadable, this will error out- used to print things that can not be read back in
• #( read a vector instead of a list (terminates with ')')
• #t true
• #. evaluates the next form and replaces itself with that evaluation
• #; read and discard the next sexp (will be an error if the sexp can not be read)
• #"_ read a string literal (see above)