AWK Curry Function - Can a function return a function?

Question

I'm working on an AWK script that quite a big mess at the moment, and I'm trying to improve it (primarily because I want to improve my Awk scripting skillz)

I realize that there isn't a way to do Object Oriented Programming within Awk or Gawk, but is there a way to at least curry functions? As in returning a function from within a function? (Not return the result of the executed function, but rather return a function that can be executed)

I found a Stack Overflow post , where @GreenFox showed that its possible to execute a function with the name of the function stored in a variable. The example he posted is below:

function foo(s){print "Called foo "s}
function bar(s){print "Called bar "s}
{
    var = "";
    if(today_i_feel_like_calling_foo){
        var = "foo";
    }else{
        var = "bar";
    }
    @var( "arg" ); # This calls function foo(), or function bar() with "arg"
}

What I'm wondering is if its possible to return a function from another function.

For example, a function that accepts a string that can be used in awks printf as a format, and returns a function that accepts two other arguments, and essentially executes printf( fmt_from_parent_func, sub_func_arg1, sub_func_arg2 ) .

Here's my attempt at trying to accomplish the following:

#! /usr/local/bin/awk -f

function setFmt ( fmt ){
  function _print ( var, val ){
    printf ( fmt ? fmt : "%-15s: %s\n" ), str1, str2
  }
  return @_print
}
BEGIN {
  fmtA = setFmt("%-5s: %s\n")
  @fmtA("ONE","TWO")
}

Which results in the errors:

awk: ./curry.awk:4:   function _print ( var, val ){
awk: ./curry.awk:4:   ^ syntax error
awk: ./curry.awk:4:   function _print ( var, val ){
awk: ./curry.awk:4:                               ^ syntax error
awk: ./curry.awk:6:     printf ( fmt ? fmt : "%-15s: %s\n" ), str1, str2
awk: ./curry.awk:6:                                                     ^ unexpected newline or end of string
awk: ./curry.awk:11:   fmtA = setFmt("%-5s: %s\n")
awk: ./curry.awk:11:                              ^ unexpected newline or end of string
awk: ./curry.awk:12:   @fmtA("ONE","TWO")
awk: ./curry.awk:12:                     ^ unexpected newline or end of string

If anyone knows if this is at all possible (which Im starting to see myself), and knows a way to accomplish something to this effect.. that would be awesome.

Thanks!

Answer 1

With GNU awk you can return the name of a function as a string from another function but you can't declare a function within another function nor can you return a function (or an array) in any awk - all you can return from a function in awk is a scalar value (ie a number or string).

Is this what you're trying to do:

$ cat tst.awk
function _print ( var, val ){
  printf _print_fmt, var, val
}

function setFmt ( fmt ){
  _print_fmt = (fmt ? fmt : "%-15s: %s\n" )
  return "_print"
}

BEGIN {
  fmtA = setFmt("%-5s: %s\n")
  @fmtA("ONE","TWO")
}

$ awk -f tst.awk
ONE  : TWO