Question

The following denotational semantics describes what

if(M1(some1, s)==error)

  return error

else if(M1(some1,s )==true)

  if(M2 (some2,s )==error)

  return error

  else s = M2 (some2, s)

else if(M1 (some1,s)==false)

  if(M2(some3,s )==error)

  return error  

  else s = M2(some3,s )

Answer 1

If the M1(some1,s) gives some error then stop the execution of the programme and return the error.

If it is not returning any error but it is returning "true" then check for the M2(some2,s) if M2 return some error then stop the exectuion of function and  return that error else assign the return value of M2(some2,s) to the s.

If the return value of M1(some1,s) is "false" then check for the M2(some3,s) if M2(some3,s) return error stop the execution and return the error, else assign the return value of M2(some3,s) to the s.