On 17/01/2013 22:01, Era Scarecrow wrote:
<snip>
As I recall for the compilers very early on, all comments and unneeded
whitespace were simply removed before compiling, leaving you with one
very long command string. The /**/ comment syntax makes perfect sense in
this case; Later tools more memory and hardware power make it more
manageable; but // requires 2d code to properly compile until the
comments are stripped.
Doesn't quite follow, because as far as the computer is concerned a line
break is just another character.
Though in order to know whether a newline is whitespace, the lexer needs
to know whether it's lexing a // comment or not. But this
context-sensitive character classification is something we already
needed in order to read strings correctly. Unless these early languages
didn't allow you to have consecutive spaces in a string literal or
required a special notation for them.
// c example, originally isprime and main don't have
// return types, defaulting to int instead.
Does the return type of a function still default to int if unspecified
in current C, either according to the ANSI standard or according to most
compilers?
int isprime(int n){int cnt=2;if(n<2)return
0;for(;cnt<n;cnt++)if((n%cnt)==0)return 0;return 1;}int main(){int
cnt=2;for(;cnt<1000000;cnt++)if (isprime(cnt))printf("%d \n", cnt);}
It's one of the reasons the syntax requires a semicolon after each
statement so it can tell obviously where something ends.
But Dennis could have easily designed it to use a newline instead of a
semicolon. Indeed, there are a number of programming languages that
basically do this.
But other languages do more than this, like Python and Haskell which are
indent-sensitive, and early FORTRAN with its strict rules on code
layout. Indeed, considering these, you could well ask where to draw the
line between a 1D language and a 2D language.
Stewart.
