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9.2.5 Functions and Their Effects on Variable Typing

awk is a very fluid language. It is possible that awk can't tell if an identifier represents a scalar variable or an array until runtime. Here is an annotated sample program:

     function foo(a)
     {
         a[1] = 1   # parameter is an array
     }
     
     BEGIN {
         b = 1
         foo(b)  # invalid: fatal type mismatch
     
         foo(x)  # x uninitialized, becomes an array dynamically
         x = 1   # now not allowed, runtime error
     }

In this example, the first call to foo() generates a fatal error, so gawk will not report the second error. If you comment out that call, though, then gawk will report the second error.

Usually, such things aren't a big issue, but it's worth being aware of them.