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printf integer format compatibility

From: John W. Eaton
Subject: printf integer format compatibility
Date: Wed, 16 Apr 2014 09:50:24 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131005 Icedove/17.0.9

While looking at some problems with printing 64-bit integer values with printf, I found that Matlab's printf function silently switches from integer formats like '%d' or '%u' to '%e' when values are not integers or when they exceed the maximum value possible for a 64-bit integer type. Matlab also seems to be ignoring size specifications for integer formats, so although formats like '%hd' (short int) are accepted, there seems to be no change in output compared to just using '%d'. And '%d' always handles up to 64-bit integers without needing 'l' or 'll'.

I checked in the following change on the default branch:


Now you can expect behavior like the following, which appears to be compatible with Matlab:

  sprintf('%d',intmin('int32'))    %% ans = -2147483648
  sprintf('%d',intmax('int32'))    %% ans = 2147483647
  sprintf('%d',intmin('int64'))    %% ans = -9223372036854775808
  sprintf('%d',intmax('int64'))    %% ans = 9223372036854775807
  sprintf('%d',intmin('uint32'))   %% ans = 0
  sprintf('%d',intmax('uint32'))   %% ans = 4294967295
  sprintf('%d',intmin('uint64'))   %% ans = 0
  sprintf('%d',intmax('uint64'))   %% ans = 1.84467e+19
  sprintf('%d',realmin('single'))  %% ans = 1.17549e-38
  sprintf('%d',realmax('single'))  %% ans = 3.40282e+38
  sprintf('%d',realmin('double'))  %% ans = 2.22507e-308
  sprintf('%d',realmax('double'))  %% ans = 1.79769e+308

There is still one difference: Matlab switches to '%e' and Octave is currently switching to '%g'. Should we follow Matlab exactly here? I generally prefer '%g' over '%e' because it seems easier to me to read numbers without unnecessary e+04 style exponents appended.

This change caused a few new test failures in cases where '%d' was previously assumed to always produce an integer result. I fixed one problem in the datestr function by rounding the printf argument that was used with a '%d' format. I could use some help fixing the stemleaf function since I'm not sure what the intent is there.


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