Power-Programmierung/CD1.mdf/qtawk/diffdoc.fmt

Text File | 1990-11-04 | 13KB | 274 lines

                     QTAwk


    A new shareware program, QTAwk.  The program is a "derivative" of  "The
    Awk Programming Language."  Four versions of the program exist for  the
    IBM PC and    clones depending on  the h/w configuration:   8086/8088, or
    80286+ and with or without 80x87 numeric co-processor.

    The QTAwk package contains many complete and sample utilities which run
    under QTAwk.

  ----------------------------------------------------------------------------

    The major differences between QTAwk and Awk are summarized below:


        Major differences between QTAwk (version 4.20) and Awk.

  1.  Expanded Regular Expressions
      All of the Awk  regular  expression  operators  are  allowed  plus  the
      following:
      a)  complemented    character  class using the Awk notation, '[^...]', as
      well as the Awk/QTAwk and C logical  negation  operator,  '[!...]'.

      b)  Matched  character  classes,    '[#...]'.  These  classes are used in
      pairs. The position of the character matched in the first class  of
      the pair, determines the character which must match in the position
      occupied by the second class of the pair.

      c)  Look-ahead Operator. r@t regular expression r is matched only  when
      followed by regular expression t.

      d)  Repetition  Operator. r{n1,n2} at least n1 and up to n2 repetitions
      of regular expression r. 1 <= n1 <= n2

      e)  Named Expressions.
      {named_expr} is replaced by the string value    of  the  corrsponding
      variable.

  2.  Consistent  statement  termination  syntax.  The QTAwk Utility Creation
      Tool utilizes the semi-colon, ';', to  terminate  all  statements.  The
      practice    in  Awk of using newlines to "sometimes" terminate statements
      is no longer allowed.

  3.  Expanded Operator Set
      The Awk set of operators has been changed to more closely  match    those
      of C. The Awk match operator, '~', has been changed to '~~' so that the
      similarity between the match operators, '~~' and '!~', to the  equality
      operators,  '=='  and  '!=", is complete. The single tilde symbol, '~',
      reverts to the C one's complement operator, an addition to the operator
      set  over  Awk.  The  introduction of the explicit string concatenation
      operator. The remaining "new" operators to QTAwk are:


      Operation         Operator
      ---------         --------
      tag            $$
      one's complement      ~
      concatenation        ∩ ( ASCII 239, 0xef character)
      shift left/right        << >>
      matching            ~~ !~
      bit-wise AND        &
      bit-wise XOR        @
      bit-wise OR        |
      sequence            ,

       The carot, '^', remains as the expoentiation operator. The symbol  '@'
      is used for the exclusive OR operator.

  4.  Expanded set of recognized constants in QTAwk utilities:
      a)  decimal integers,
      b)  octal integers,
      c)  hexadecimal integers,
      d)  character constants, and
      e)  floating point constants.

  5.  Expanded Pre-defined patterns giving more control:
      a)  INIITAL  -  similar  to  BEGIN. Actions executed after opening each
      input file and before reading first record.
      b)  FINAL - similar to END. Actions executed after reading last  record
      of each input file and before closing file.
      c)  NOMATCH  -  actions  executed  for  each  input record for which no
      pattern was matched.
      d)  GROUP - used to  group  multiple  regular  expressions  for  search
      optimization. Can speed search by a factor of six.

  6.  True multi-dimensional arrays
      The  use    of  the comma in index expressions to simulate multiple array
      indices is no longer supported. True multiple  indices  are  supported.
      Indexing    is in the C manner, 'a[i1][i2]'. The SUBSEP built-in variable
      of AWK has been dropped since it is no longer necessary.

  7.  Integer array indices as well as string indices
      Array indices have been expanded to include integers  as    well  as  the
      string  indices  of  Awk.  Indices  are  not automatically converted to
      strings as in Awk. Thus, for true integer indices, the  index  ordering
      follows  the  numeric  sequence  with  an  integer  index value of '10'
      following a value of '2' instead of preceeding it.

  8.  Arrays integrated into QTAwk
      QTAwk  integrates   arrays  with    arithmetic  operators  so  that   the
      operations  are  carried out on the entire array. QTAwk also integrates
      arrays into user-defined functions so that they can be  passed  to  and
      returned    from  such  functions  in a natural and intuitive manner. Awk
      does not allow returning arrays from user-defined  functions  or    allow
      arithmetic operators to operate on whole arrays.

  9.  NEW keywords:

      a)  cycle
      similar  to 'next' except that may use current record in restarting
      outer pattern matching loop.
      b)  deletea
      similiar to 'delete' except that ALL array values deleted.
      c)  switch, case, default
      similiar to C syntax with the allowed 'switch'  and  'case'  values
      expanded  to    include  any  legal  QTAwk  expression,  evaluated at
      run-time. The expressions may evaluate to any value  including  any
      numeric value, string or regular expression.
      d)  local
      new  keyword    to  allow  the declaration and use of local variables
      within compound statements, including user-defined  functions.  Its
      use  in  user  defined  functions  instead  of  the Awk practice of
      defining excess formal parameters, leads  to    easier    to  read  and
      maintain  functions. The C 'practice' of allowing initialization in
      the 'local' statement is followed.
      e)  endfile
      similar to 'exit'. Simulates end of current input  file  only,  any
      remaining input files are still processed.

  10. Expanded arithmetic functions
      QTAwk  includes  18 built-in arithmetic functions. All of the functions
      supported by Awk plus the following:
      a)  acos(x)
      b)  asin(x)
      c)  cosh(x)
      d)  fract(x)
      e)  log10(x)
      f)  pi() or pi
      g)  sinh(x)

  11. Expanded string functions
      QTAwk includes 33 built-in  string  functions.  All  of  the  functions
      supported by Awk plus the following:
      a)  center(s,w) or center(s,w,c)
      b)  copies(s,n)
      c)  deletec(s,p,n)
      d)  insert(s1,s2,p)
      e)  justify(a,n,w) or justify(a,n,w,c)
      f)  overlay(s1,s2,p)
      g)  remove(s,c)
      h)  replace(s)
      i)  sdate(fmt)
      j)  srange(c1,c2)
      k)  srev(s)
      l)  stime(fmt)
      m)  stran(s) or stran(s,st) or stran(s,st,sf)
      n)  strim(s) or strim(s,c) or strim(s,c,d)
      o)  strlwr(s)
      p)  strupr(s)

  12. New Miscellaneous functions
      a)  The  function 'rotate(a)' is provided to rotate the elements of the
      array a.
      b)  execute(s) or execute(s,se) or execute(s,se,rf) - execute string  s
      c)  execute(a)  or  execute(a,se) or execute(a,se,rf) - execute array a
      d)  pd_sym - access pre-defined symbols
      e)  ud_sym - access user defined symbols

  13. New I/O  Functions
      I/O  function  syntax  has  been    made  consistent with syntax of other
      functions.  The redirection operators, '<', '>' and '>>', and  pipeline
      operator,  '|',  have  been  deleted  as  excessively  error  prone  in
      expressions.  The functional syntax of the 'getline' function has  been
      made  identical  to  that  of  the  other  built-in functions.  The new
      functions 'fgetline', 'fprint' and  'fprintf' have been introduced  for
      reading and writing to files other than the current input file.  Single
      Character input functions, 'getc' and  'fgetc' have been added to  read
      files (and the keyboard) a single character at a time.

  14. Expanded capability of  formatted I/O.
      The limited output formatting available with the Awk 'printf'  function
      has been expanded by adopting the complete output format    specification
      of the draft ANSI C standard.

  15. Use of 'local' keyword
      The 'local' keyword has been introduced to allow for variables local to
      user-defined  functions  (and  any  compound statement). This expansion
      makes the Awk practice of defining 'extra' formal parameters no  longer
      necessary.

  16. Expanded user-defined functions
      With  the  'local'  keyword,  QTAwk allows the user to define functions
      that may accept a variable number  of  arguments.  Functions,  such  as
      finding  the  minimum/maximum  of  a  variable number of variables, are
      possible with one function rather than defining separate functions  for
      each possible combination of arguments.

  17. User controlled trace capability
      A user controlled statement trace capability has been added. This gives
      the user a simple to use mechanism to trace utility  execution.  Rather
      than  adding  'print'  statements,  merely  re-defining  the value of a
      built-in    variable  will    give  utility  execution  trace  information,
      including utility line number.

  18. Expanded built-in variable list
      With  30    built-in variables, QTAwk includes all (with the exception of
      SUBSEP) of the built-in variables of Awk plus the following:
      a)  _arg_chk - used to determine whether to check number    of  arguments
      passed to user-defined functions.
      b)  ARGI    -  index  value  in ARGV of next command line argument. Gives
      more control of command line argument processing.
      c)  CYCLE_COUNT - count number of outer loop cycles with current    input
      record.
      d)  DEGREES  -  if  TRUE, trigonometric functions assume degree values,
      radians if FALSE.
      e)  ENVIRON - array of environment strings passed to QTAwk
      f)  FALSE - pre-defined with constant value, 0.
      g)  TRUE - predefined with constant value, 1
      h)  LONGEST_EXP - used to control whether  the  longest  or  the    first
      string matching a regular expression is found.
      j)  MAX_CYCLE  -    maximum  number  of  outer loop cycles permitted with
      current input record.
      k)  NG - equal to the number of  the  regular  expression  in  a    group
      matching a string in the current input record.
      k)  RETAIN_FS  -    if TRUE the original characters separating the fields
      of the current input    record    are  retained  whenever  a  field  is
      changed,  causing  the  input record to be re-constructed. If FALSE
      the output field separator, OFS, is used to separate fields in  the
      current  input record during reconstruction. The latter practice is
      the only method available in Awk.
      l)  TRACE - value used to determine utility tracing.
      m)  TRANS_FROM/TRANS_TO - strings used by 'stran'  function  if  second
      and/or third arguments not specified.
      n)  CLENGTH - similiar to 'RLENGTH' of Awk. Set whenever a 'case' value
      evaluates to a regular expression.
      o)  CSTART - similiar to 'RSTART' of Awk. Set whenever a  'case'  value
      evaluates to a regular expression.
      p)  MLENGTH  - similiar to 'RLENGTH' of Awk. Set whenever a stand-alone
      regular expression is encountered in evaluting a pattern.
      q)  MSTART - similiar to 'RSTART' of Awk. Set  whenever  a  stand-alone
      regular expression is encountered in evaluting a pattern.
      r)  vargc - used only in used-defined functions defined with a variable
      number of arguments. At runtime, set equal to the actual number  of
      variable arguments passed.
      s)  vargv - used only in used-defined functions defined with a variable
      number of arguments. At runtime, an single dimensioned  array  with
      each element set to the argument actually passed.

  19. Definition of built-in variable, RS, expanded to mimic the FS built-in
      variable.  For A single character string, the single character  becomes
      the input  record separator.   If  the string  is longer    than a single
      character,  it  is  treated  as  a  regular  expression, and any string
      matching the regular expression becomes  a record separator.  Awk  will
      recognize first character only of RS string as record delimitor.

  20. In QTAwk, setting built-in variable, "FILENAME", to another value will
      change the current  input file.    Setting the variable  in Awk, has  no
      effect on current input file.

  21. New character input functions, 'getc' and 'fgetc', can accept keyboard
      input also.

  22. Corrected admitted problems with Awk. The problems mentioned  on    page
      182   of     "The   Awk   Programming   Language"  have  been  corrected.
      Specifically: 1) true multi-dimensional arrays have  been  implemented,
      2) the 'getline' syntax has been made to match that of other functions,
      3)  declaring  local  variables  in  user-defined  functions  has  been
      corrected,  4) intervening blanks are allowed between the function call
      name and the opening parenthsis (in fact, under QTAwk it is permissable
      to  have    no  opening  parenthesis  or  argument    list for user-defined
      functions that have been defined with no formal arguments).