SICP using JS > rational

rational.js

function pair(a, b) {
    return function(i) {
        if (i === 0) return a
        else return b
    }
}
function head(p) {
    return p(0)
}
function tail(p) {
    return p(1)
}
var make_rat = pair
var numer = head
var denom = tail

function add_rat(r1, r2) {
    var n = numer(r1) * denom(r2) + numer(r2) * denom(r1)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function sub_rat(r1, r2) {
    var n = numer(r1) * denom(r2) - numer(r2) * denom(r1)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function mul_rat(r1, r2) {
    var n = numer(r1) * numer(r2)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function div_rat(r1, r2) {
    var n = numer(r1) * denom(r2)
    var d = denom(r1) * numer(r2)
    return make_rat(n, d) 
}

function is_equal(r1, r2) {
    return numer(r1) * denom(r2) === denom(r1) * numer(r2)
}

function print_rat(r) {
    return "(" + numer(r) + "/" + denom(r) + ")"
} 
debugger
var r1 = make_rat(25, 10)
var r2 = make_rat(2, 10)
var result = mul_rat(r1, r2)
print_rat(result)

rational2.js

function gcd(a,b) {
   return b === 0 ? a : gcd(b, a % b);
}

function pair(a, b) {
    return function(i) {
        if (i === 0) return a
        else return b
    }
}
function head(p) {
    return p(0)
}
function tail(p) {
    return p(1)
}
var make_rat = pair
var numer = head
var denom = tail

function add_rat(r1, r2) {
    var n = numer(r1) * denom(r2) + numer(r2) * denom(r1)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function sub_rat(r1, r2) {
    var n = numer(r1) * denom(r2) - numer(r2) * denom(r1)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function mul_rat(r1, r2) {
    var n = numer(r1) * numer(r2)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function div_rat(r1, r2) {
    var n = numer(r1) * denom(r2)
    var d = denom(r1) * numer(r2)
    return make_rat(n, d) 
}

function is_equal(r1, r2) {
    return numer(r1) * denom(r2) === denom(r1) * numer(r2)
}

function print_rat(r) {
    return "(" + numer(r) + "/" + denom(r) + ")"
} 

function simplify(r) {
    var n = numer(r)
    var d = denom(r)
    var divisior = gcd(n, d) 
    return make_rat(n/divisior, d/divisior)
}

function print_simplified_rat(r) {
    return print_rat(simplify(r))
} 

var r1 = make_rat(25, 10)
var r2 = make_rat(2, 10)
var result = mul_rat(r1, r2)
print_simplified_rat(result)

rational3.js

function gcd(a,b) {
   return b === 0 ? a : gcd(b, a % b);
}

function pair(a, b) {
    return function(i) {
        if (i === 0) return a
        else return b
    }
}
function head(p) {
    return p(0)
}
function tail(p) {
    return p(1)
}
var make_rat = function(n, d){
    var div = gcd(n, d)
    pair(n/div, d/div)
}
var numer = head
var denom = tail

function add_rat(r1, r2) {
    var n = numer(r1) * denom(r2) + numer(r2) * denom(r1)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function sub_rat(r1, r2) {
    var n = numer(r1) * denom(r2) - numer(r2) * denom(r1)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function mul_rat(r1, r2) {
    var n = numer(r1) * numer(r2)
    var d = denom(r1) * denom(r2)
    return make_rat(n, d)
}

function div_rat(r1, r2) {
    var n = numer(r1) * denom(r2)
    var d = denom(r1) * numer(r2)
    return make_rat(n, d) 
}

function is_equal(r1, r2) {
    return numer(r1) * denom(r2) === denom(r1) * numer(r2)
}

function print_rat(r) {
    return "(" + numer(r) + "/" + denom(r) + ")"
} 

var r1 = make_rat(25, 10)
var r2 = make_rat(2, 10)
var result = mul_rat(r1, r2)
print_rat(result)