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macroexpand

macroexpand(x)

Takes the expression x and returns an equivalent expression with all macros removed (expanded).

Examples

1. Expand macros in an expression:

   julia> macroexpand(:(@time sum(rand(100))))
   quote
      local #stats#550 = Base.gc_num()
      local #elapsed#551 = Base.time_ns()
      local #val#552 = sum(rand(100))
      local #elapsed#553 = Base.time_ns() - #elapsed#551
      local #diff#554 = Base.gc_num() - #stats#550
      (Base.time_println)("#elapsed#553 seconds (",Base.time_format_elf(0.001 * #elapsed#553)," CPU)",(Base.gc_num)()," collections, ",(Base.gc_alloc_count)()," allocations, ",Base.gc_alloc_bytes()," bytes allocated")
      #val#552
   end

   The macroexpand function expands the macro @time and returns the equivalent expression with the macro removed.

2. Expand nested macros:

   julia> macroexpand(:(@time begin
          @show 2 + 2
          @time 3 * 3
      end))
   quote
      local #stats#555 = Base.gc_num()
      local #elapsed#556 = Base.time_ns()
      begin
          local #val#557 = begin
                  local #stats#558 = Base.gc_num()
                  local #elapsed#559 = Base.time_ns()
                  begin
                      local #val#560 = 2 + 2
                      (Base.time_println)("2 + 2 = ",#val#560)
                      #val#560
                  end
              end
          local #elapsed#561 = Base.time_ns() - #elapsed#559
          local #diff#562 = Base.gc_num() - #stats#558
          (Base.time_println)("#elapsed#561 seconds (",Base.time_format_elf(0.001 * #elapsed#561)," CPU)",(Base.gc_num)()," collections, ",(Base.gc_alloc_count)()," allocations, ",Base.gc_alloc_bytes()," bytes allocated")
          #val#557
      end
   end

   This example demonstrates the expansion of nested macros using macroexpand.

Common mistake example:

julia> macroexpand(@unknown_macro)
ERROR: UndefVarError: @unknown_macro not defined

Here, the @unknown_macro is not a defined macro, resulting in an error. Ensure that the macro used with macroexpand is valid and defined in the Julia environment.

See Also

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