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2253 :: parsing statement list expressions

• nimfoo (orginal) [2016-05-11T03:59:26+02:00] view original

  macros.nim has parseStmt() to parse statements, and parseExpr() to parse expressions, but nothing that I see to parse statement list expressions, which is node type nnkStmtListExpr.

  I'm writing macros to preprocess code at compile-time, and would love a parseStmts() proc so I could use ";" between statements within preprocessed code blocks.

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• Araq (orginal) [2016-05-11T12:59:42+02:00] view original

  import macros
  
  macro m(): untyped =
    result = parseStmt"""
  echo "foo"
  echo "bar"
    """
  
  m()
  Run

  Stmt can be a list of statements.

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• OderWat (orginal) [2016-05-11T13:15:52+02:00] view original

  Or

  import macros
  
  macro m(): untyped =
    result = parseStmt"""(echo "foo"; echo "bar")"""
  
  m()
  Run

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• nimfoo (orginal) [2016-05-17T22:55:01+02:00] view original

  Thank you Araq and OderWat.

  I was able to take your examples and use it to evaluate a const statement list expression string:

  macro tripleParseStmt*(s: string): untyped =
   let tmp = "(" & s.strVal & ")"
   result = parseStmt(tmp)
  
  tripleParseStmt("""echo "foo2"; echo "bar2"""")    # works.
  const s3 = """echo "foo3"; echo "bar3""""
  tripleParseStmt($s3)                               # works if I stringify a const string.
  
  Run

  It works outside a macro, but I was hoping to call tripleParseStmt from inside a macro, on a variable created within the macro, but that shows this message: Error: field 'strVal' cannot be found.

  I also tried calling parseStmt() from within my macro using "(" .. ")":

  var mybody = parseStmt("(" & res2[i] & ")")
  Run

  That shows "Error: invalid indentation", which is what I was getting before when parsing strings containing ";".

  I wish there was a magical, built-in parseStmts() proc to handle statement list expressions.

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