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419 :: How can I force macro input parameters to be a string?

• gradha (orginal) [2014-04-13T17:33:08+02:00] view original

  The following example illustrates a problem with macro parameters. Save this as a test.nim:

  
  import macros, strutils, os
  
  macro test_paths(path: string): stmt =
    let input = slurp(path.strVal)
    for line in input.splitLines:
      echo "Did read ", line.strip
    
    result = newNimNode(nnkStmtList)
  
  when isMainModule:
    test_paths("test.nim")
    test_paths("."/"test.nim")
  Run

  When compiled, the file will process the first macro and will fail on the second one:

  
  stack trace: (most recent call last)
  test.nim(4)              test_paths
  test.nim(4, 24) Error: field 'strVal' cannot be found
  Run

  I understand that in the case of the second invocation rather than a string the macro is receiving the whole / operator call with two parameters. Is there a helper which goes through the input parameters and processes them to always return a string? If I try to use macro.$ on the path parameter it SIGSEVs.

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• LeuGim (orginal) [2014-04-13T19:08:03+02:00] view original

  Works with static:

  import macros, strutils, os
  
  macro test_paths(path: static[string]): stmt =
    let input = slurp(path)
    for line in input.splitLines:
      echo "Did read ", line.strip
    
    result = newNimNode(nnkStmtList)
  
  when isMainModule:
    test_paths("test.nim")
    test_paths("."/"test.nim")
  Run

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