chained_comparisons.sjs

macro $if {
    rule {
        ($x...)
    } => {
        if (relCar($x...))
    }
}

macro $while {
    rule {
        ($x...)
    } => {
        while (relCar($x...))
    }
}

// naive form:
/*
macro rel {
    rule {$x} => { $x }
    rule {($x:ident $op $y:ident $rest ...)} => {
        $x $op $y && $rel($y $rest ...)
    }
}
*/

// better: works even with the presence of &&, |, etc.
macro relGen {
    rule {
        ($cmp...)
    } => {
        macro relCar {
            $(rule {
                ($x $cmp $y $rest $[...])
            } => {
                $x $cmp $y relCdr($y $rest $[...])
            })...
            rule {
                $x
            } => {
                $x
            }
        }

        macro relCdr {
            $(rule {
                ($y $cmp $z)
            } => { && $y $cmp $z
            })...
            /* since the following two sequences are of equal length, order is important */
            rule {
                ($y: ident $op $z: ident $rest $[...])
            } => {
                $op relCar($z $rest $[...])
            }
            $(rule {
                ($y: ident $cmp $z: ident $rest $[...])
            } => { && $y $cmp $z relCdr($z $rest $[...])
            })...
            rule {
                $y
            } => {
                $y
            }
        }
    }
}

relGen(>= <= > < != !== === ==)

$while(1 > 2 > 3 >= 4 <= 5 > 6) {
    console.log("foo");
}

$if(1 < 2 < 3 < 4 < 5 < 6) {
    console.log("bar");
}

$if(1 < 2 && 3 < 4 < 5 || 1 == 2 == 3) {
    console.log("bar");
}

// result:
/*
while (1 > 2 && 2 > 3 && 3 >= 4 && 4 <= 5 && 5 > 6) {
console.log('foo');
}
if (1 < 2 && 2 < 3 && 3 < 4 && 4 < 5 && 5 < 6) {
console.log('bar');
}
if (1 < 2 && 3 < 4 && 4 < 5 || 1 == 2 && 2 == 3) {
console.log('bar');
}
*/