Solutions to the Exercises of Episode 7

1. Currently, Squaak only has grammar rules for integer and string constants, not floating point constants. Implement this grammar rule. A floating-point number consists of zero or more digits, followed by a dot and at least one digit, or, at least one digit followed by a dot and any number of digits. Examples are: 42.0, 1., .0001. There may be no whitespace between the individual digits and the dot. Make sure you understand the difference between a "rule" and a "token".

token float_constant {
    [
    | \d+ '.' \d*
    | \d* '.' \d+
    ]
    {*}
}

2. Implement the missing operators: (binary) "-", "<=", ">=", "==", "!=", "/", "%", "or"

For sake of completeness (and easy copy-paste for you), here's the list of operator declarations as I wrote them for Squaak:

rule expression is optable { ... }

proto 'infix:or' is precedence('1')
                 is pasttype('unless') { ... }
proto 'infix:and' is tighter('infix:or')
                  is pasttype('if') { ... }

proto 'infix:<'   is tighter('infix:and') { ... }
proto 'infix:<='  is equiv('infix:<') { ... }
proto 'infix:>'   is equiv('infix:<') { ... }
proto 'infix:>='  is equiv('infix:<') { ... }
proto 'infix:=='  is equiv('infix:<') { ... }
proto 'infix:!='  is equiv('infix:<') { ... }

proto 'infix:+'   is tighter('infix:<')
                  is pirop('n_add')   { ... }
proto 'infix:-'   is equiv('infix:+')   
                  is pirop('n_sub')   { ... }

proto 'infix:..'  is equiv('infix:+')   
                  is pirop('n_concat') { ... }

proto 'infix:*'   is tighter('infix:+') 
                  is pirop('n_mul')     { ... }
proto 'infix:%'   is equiv('infix:*')   
                  is pirop('n_mod')     { ... }
proto 'infix:/'   is equiv('infix:*')   
                  is pirop('n_div')     { ... }

proto 'prefix:not' is tighter('infix:*')   
                   is pirop('n_not')   { ... }
proto 'prefix:-'   is tighter('prefix:not')
                   is pirop('n_neg')   { ... }

proto 'term:'      is tighter('prefix:-') 
                   is parsed(&term)      { ... }