Adding Regexps to Egg

Here we will add a function RegExp to the Egg interpreter allowing the creation of Regular Expression objects.

Example

examples/regexp.egg

 egg-oop-parser-solution git:(master) ✗ cat examples/regexp.egg
(
  def(d, r/
         (?<year>  \d{4} ) -?  # year 
         (?<month> \d{2} ) -?  # month 
         (?<day>   \d{2} )     # day
        /x),
  print(d.test("1987-07-14")),  # true
  def(m, d.exec("1987-07-14")),  
  print(util.inspect(m, {depth: null})),   /*  [  '1987-07-14',  '1987',  '07',  '14',  index: 0,  input: '1987-07-14',  groups: undefined ] */
  print(m.index), # 0
  
  def(x, RegExp.exec("2015-01-22", d)), 
  print(util.inspect(x, {depth: null})),
  print(x.year), # 2015
  print(x.month) # 02
)

The interpreter provided for this lab is not able to handle regular expressions. The following error is produced when trying to run the example above:

➜  egg-oop-parser-solution git:(master) ✗ bin/eggc.js examples/regexp.egg
➜  egg-oop-parser-solution git:(master) ✗ bin/evm examples/regexp.json
TypeError: Applying not a function or method TypeError: Applying not a function or method TypeError: Applying not a function or method ReferenceError: Undefined variable: util
    at Apply.evaluate (/snapshot/2122-dist-egg/index.js:2:1230)

The error is about util not being defined.

But if I use the interpreter provided in the repo ULL-ESIT-PL/private-egg (opens in a new tab) (private repo):

egg-oop-parser-solution git:(master) ✗ ls -l bin
total 24
-rwxr-xr-x  1 casianorodriguezleon  staff   215 22 abr 13:10 egg
-rwxr-xr-x  1 casianorodriguezleon  staff  1678 22 abr 12:29 eggc.js
lrwxr-xr-x  1 casianorodriguezleon  staff    85 22 abr 12:32 evm -> /Users/casianorodriguezleon/campus-virtual/shared/egg/oop-evm-releases/evm-2122-macos
lrwxr-xr-x  1 casianorodriguezleon  staff    78 23 abr 10:57 evm-crguezl.js -> /Users/casianorodriguezleon/campus-virtual/shared/egg/eloquentjsegg/bin/evm.js
-rwxr-xr-x  1 casianorodriguezleon  staff   106 19 abr  2023 make-test

the example runs correctly:

➜  egg-oop-parser-solution git:(master) ✗ bin/evm-crguezl.js examples/regexp.json
true
[
  '1987-07-14',
  '1987',
  '07',
  '14',
  index: 0,
  input: '1987-07-14',
  groups: undefined
]
0
[
  '2015-01-22',
  '2015',
  '01',
  '22',
  index: 0,
  input: '2015-01-22',
  groups: undefined,
  year: '2015',
  month: '01',
  day: '22'
]
2015
01

This means the release must be updated for next course 24/25.

tokens.js

src/token.js, branch:main egg-oop-parser-solution

...
const REGEXP = /(?<REGEXP>r\/((?:[^\/\\]|\\.)*)\/(\w*?\b)?)/;
REGEXP.value = (value) => {
  let [source, flags] = value.split('/').slice(1);
  return {
      type: 'RegExp',
      info: [ source, flags]
  };
};

grammar.js

src/egg.ne, branch:main egg-oop-parser-solution

      %STRING  optProperties   {% buildStringValue %}
    | %NUMBER  optProperties   {% buildNumberValue %}
    | %REGEXP  optProperties   {% buildRegexpValue %}
    | bracketExp optProperties {% buildArray %}
    | curlyExp   optProperties {% buildObject %}
    | "(" commaExp ")"         {% buildDo %}
    | %WORD applies            {% buildWordApplies %}

buildRegexpValue

src/build-ast.js, branch:main egg-oop-parser-solution

function buildRegexpValue([regexpnode, properties]) {
  if (!properties) {
    regexpnode.type = "value";
    return regexpnode;
  }
  return fromListToAST(regexpnode, properties);
}

j2a.js

lib/j2a.js, branch:main eloquentjs

const {j2a, json2AST, topEnv} = require("./registry.js");
const {Value, Word, Apply, Property} = require("./ast.js");
 
j2a['value'] = (j) => { 
  let obj = new Value(j);
      // Lift the object if required
    if (typeof obj.value === "object" && obj.value.type && topEnv[obj.value.type] && typeof topEnv[obj.value.type] === "function") {
      debugger;
      try {
        obj.value = new topEnv[obj.value.type](...obj.value.info);
      } catch (e) {
        throw new TypeError(`Invalid attempt to create an ${obj.value.type}. Object value: ${obj.value}`);
      }
    }
 
  return obj;
};
j2a['word']  = (j) => new Word(j);
j2a['apply'] = (j) => {... };
 
j2a['property'] = (j) => { ...};
 
module.exports = { j2a, json2AST };

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