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0 points37ef_ced34y ago0 comments

This is a toy problem to illustrate that CoPilot cannot write code that requires mathematical reasoning. It regurgitates solutions from the training set, via a mixed internal reresentation.

0 comments

deanmen4y ago

   unsigned int swapbits(unsigned int a)
   {
       bool bit6 = a & (1 << 5);
       bool bit17 = a & (1 << 16);
       if (bit6 == bit17) return a; //bits are the same, do nothing
       return (a ^ (1 << 5) ^ (1 << 16)); // flip both 6th and 17th bits
   }

errcorrectcode4y ago

Gross and not portable C99.

    #define B6 (1<<5)
    #define B17 (1<<16)

    unsigned swapbits(unsigned a) {
       return ((a & B6 == a & B17) ? a : (a ^ (B6 | B17)));
    }

Here's some BFP:

    unsigned swapbits(unsigned a) {
       unsigned flip = (a & B6 == a & B17);
       return (a ^ ((flip<<5) | (flip<<16)));
    }

int and double are C's implicit lingua francas for underspecified literals and implicit type conversions. Throwing int everywhere is redundant like "ATM machine."

deanmen4y ago

The definition of flip requires parenthesis (a & B6) == (a & B17) as == has higher precedence than and. int is required in C++ but not in C as you said.

dskloet4y ago

What requires mathematical reasoning? Getting or setting the nth bit? Or swapping two variables? What am I missing?

j / k navigate · click thread line to collapse

0 comments

deanmen4y ago

   unsigned int swapbits(unsigned int a)
   {
       bool bit6 = a & (1 << 5);
       bool bit17 = a & (1 << 16);
       if (bit6 == bit17) return a; //bits are the same, do nothing
       return (a ^ (1 << 5) ^ (1 << 16)); // flip both 6th and 17th bits
   }

errcorrectcode4y ago

Gross and not portable C99.

    #define B6 (1<<5)
    #define B17 (1<<16)

    unsigned swapbits(unsigned a) {
       return ((a & B6 == a & B17) ? a : (a ^ (B6 | B17)));
    }

Here's some BFP:

    unsigned swapbits(unsigned a) {
       unsigned flip = (a & B6 == a & B17);
       return (a ^ ((flip<<5) | (flip<<16)));
    }

int and double are C's implicit lingua francas for underspecified literals and implicit type conversions. Throwing int everywhere is redundant like "ATM machine."

deanmen4y ago

The definition of flip requires parenthesis (a & B6) == (a & B17) as == has higher precedence than and. int is required in C++ but not in C as you said.

dskloet4y ago

What requires mathematical reasoning? Getting or setting the nth bit? Or swapping two variables? What am I missing?

j / k navigate · click thread line to collapse