Approximate PI with the aid of Wallis' product

wallis.tcl

#!/usr/bin/tclsh

#
# approximate PI with the aid of Wallis' product
#

proc wallis {{n 1000000}} {
    set value 1.0
    set i 1

    while {$i < $n} {
        set i2 [expr {($i*2)**2}]

        set value [expr {$value * $i2 / ($i2-1)}]
        incr i
    }

    return $value
}


puts [expr {2 * [wallis]}]

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