TXL solution to [[TIL Chairmarks]] #4.2: Collecting statement statistics.

-- Main.JamesCordy - 28 Oct 2005


_File "TILstats.Txl"_


<verbatim>
% Gather statement statistics for a Tiny Imperative Language program
% Jim Cordy, October 2005

% Gathers and outputs statistics on the number of each kind of statement
% in a program.  Replaces the program itself with an empty one.

% Begin with the TIL base grammar
include "TIL.Grm"

% Compute and output statement kind statistics, replace program with an empty one.
% There are many different ways to do this - this naive way is simple and
% obvioulsy correct, but exposes TXL's need for generics.  
% Another less clear solution could use polymorphism to avoid the repetition.

function main
	 replace [program]
		  Program [program]

	 % Count each kind of statement we're interested in
	 % by extracting all of each kind from the program

	 construct Statements [statement*]
		  _ [^ Program]
	 construct StatementCount [number]
		  _ [length Statements] [putp "Total: %"]

	 construct Declarations [declaration*]
		  _ [^ Program]
	 construct DeclarationsCount [number]
		  _ [length Declarations] [putp "Declarations: %"]

	 construct Assignments [assignment_statement*]
		  _ [^ Program]
	 construct AssignmentsCount [number]
		  _ [length Assignments] [putp "Assignments: %"]

	 construct Ifs [if_statement*]
		  _ [^ Program]
	 construct IfCount [number]
		  _ [length Ifs] [putp "Ifs: %"]

	 construct Whiles [while_statement*]
		  _ [^ Program]
	 construct WhileCount [number]
		  _ [length Whiles] [putp "Whiles: %"]

	 construct Fors [for_statement*]
		  _ [^ Program]
	 construct ForCount [number]
		  _ [length Fors] [putp "Fors: %"]

	 construct Reads [read_statement*]
		  _ [^ Program]
	 construct ReadCount [number]
		  _ [length Reads] [putp "Reads: %"]

	 construct Writes [write_statement*]
		  _ [^ Program]
	 construct WriteCount [number]
		  _ [length Writes] [putp "Writes: %"]

	 by
		  % nothing
end function
</verbatim>


_Example run:_


<verbatim>
<linux> cat factors.til
// Factor an input number
var n;
write "Input n please";
read n;
write "The factors of n are";
var f;
f := 2;
while n != 1 do
	 while (n / f) * f = n do
		  write f;
		  n := n / f;
	 end
	 f := f + 1;
end
<linux> txl factors.til TILstats.Txl
TXL v10.4a (15.6.05) (c)1988-2005 Queen's University at Kingston
Compiling TILstats.Txl ... 
Parsing factors.til ...
Transforming ...
Total: 11
Declarations: 2
Assignments: 3
Ifs: 0
Whiles: 2
Fors: 0
Reads: 1
Writes: 3
<linux> 
</verbatim>