Posted to tcl by kbk at Fri Jun 12 20:53:06 GMT 2009view pretty
namespace path ::tcl::mathop proc TRACE {} { puts [format %*s%s [info level] {} [info level [- [info level] 1]]] } proc TRACE args {} proc fib {n {c {{x} {set x}}}} { # apply c to nth element of fibonacci seq TRACE if {$n < 2} { tailcall apply $c $n } else { tailcall fib1 $n $c } } proc fib1 {n c} { # apply c to nth element of fibonacci sequence (n >= 2) TRACE tailcall -c $n 1 [list [list nm1 [list n $n] [list c $c]] { tailcall fib2 $nm1 $n $c }] } proc fib2 {nm1 n c} { # apply c to nth element of fibonacci sequence # n-1 has been completed and placed in $nm1 TRACE tailcall -c $n 2 [list [list nm2 [list nm1 $nm1] [list c $c]] { tailcall fib3 $nm1 $nm2 $c }] } proc fib3 {nm1 nm2 c} { # apply c to nth element of Fibonacci sequence. # n-1 and n-2 have been computed and placed in nm1 # and nm2 TRACE tailcall fib $nm1 [list [list fibnm1 [list nm2 $nm2] [list c $c]] { tailcall fib4 $fibnm1 $nm2 $c }] } proc fib4 {fibnm1 nm2 c} { # apply c to nth element of Fibonacci sequence. # (n-1)st element is known. TRACE tailcall fib $nm2 [list [list fibnm2 [list fibnm1 $fibnm1] [list c $c]] { tailcall +c $fibnm1 $fibnm2 $c }] } proc +c {x y c} { # apply c to the sum of x and y TRACE tailcall apply $c [+ $x $y] } proc -c {x y c} { # apply c to the difference of x and y TRACE tailcall apply $c [- $x $y] } puts [fib 5]