Why is this program erroneously rejected by three C++ compilers?

Question

Originally from Overv @ reddit.

Try this way:

Your < and >, ( and ), { and } don't seem to match very well; Try drawing them better.

In the standard, §2.1/1 specifies:

Physical source file characters are mapped, in an implementation-defined manner, to the basic source character set (introducing new-line characters for end-of-line indicators) if necessary.

Your compiler doesn't support that format (aka cannot map it to the basic source character set), so it cannot move into further processing stages, hence the error. It is entirely possible that your compiler support a mapping from image to basic source character set, but is not required to.

Since this mapping is implementation-defined, you'll need to look at your implementations documentation to see the file formats it supports. Typically, every major compiler vendor supports (canonically defined) text files: any file produced by a text editor, typically a series of characters.

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Note that the C++ standard is based off the C standard (§1.1/2), and the C(99) standard says, in §1.2:

This International Standard does not specify
— the mechanism by which C programs are transformed for use by a data-processing system;
— the mechanism by which C programs are invoked for use by a data-processing system;
— the mechanism by which input data are transformed for use by a C program;

So, again, the treatment of source files is something you need to find in your compilers documentation.

You could try the following python script. Note that you need to install PIL and pytesser.

from pytesser import *
image = Image.open('helloworld.png')  # Open image object using PIL
print image_to_string(image)     # Run tesseract.exe on image

To use it, do:

python script.py > helloworld.cpp; g++ helloworld.cpp

You forgot to use Comic Sans as a font, that's why its erroring.