Path: blob/master/source/cprogramming/Ex_3.4_itoa-2.rst
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====================================================== Exercise 3.4 - itoa to handle largest negative integer ====================================================== Question ======== In a two's complement number representation, our version of itoa does not handle the largest negative number, that is, the value of n equal to -(2wordsize-1). Explain why not. Modify it to print that value correctly, regardless of the machine on which it runs. The previous version of itoa was this:: .. literalinclude:: ../../languages/cprogs/Ex_3.4_itoa-previous.c :language: c :tab-width: 4 .. literalinclude:: ../../languages/cprogs/Ex_3.4_itoa-2.c :language: c :tab-width: 4 .. runcode:: ../../languages/cprogs/Ex_3.4_itoa-2.c :language: c :codesite: ideone Explanation =========== In this version of itoa, which involves a largest negative number, we first store the number itself in an integer called sign. Then get numbers from unittest by doing `n%10`, get the unsigned number by doing a `abs` value and get character by adding it to `0`. Thus we go about converting each digit starting from unit place to a character. Once this process is over. We check if we were converting negative number, by checking if the sign is less than 0, if it was, we add a `-` to the string. And then we do a simple `reverse` of the string to get our `itoa`. .. seealso:: * :c-suggest-improve:`Ex_3.4_itoa-2.c` * :c-better-explain:`Ex_3.4_itoa-2.rst`