Order two numerical lists

From Rosetta Code
Task
Order two numerical lists
You are encouraged to solve this task according to the task description, using any language you may know.

Write a function that orders two lists or arrays filled with numbers. The function should accept two lists as arguments and return true if the first list should be ordered before the second, and false otherwise.

The order is determined by lexicographic order: Comparing the first element of each list. If the first elements are equal, then the second elements should be compared, and so on, until one of the list has no more elements. If the first list runs out of elements the result is true. If the second list or both run out of elements the result is false.

Note: further clarification of lexicographical ordering is expounded on the talk page here and here.

ACL2[edit]

The built-in lexorder does this.

ACL2 !>(lexorder '(1 2 3) '(1 2 3 4))
T
ACL2 !>(lexorder '(1 2 4) '(1 2 3))
NIL

Ada[edit]

This is already implemented in the built-in comparison operators for arrays of types that have a direct ordering. This also includes arrays of user defined types, using the type definition order from smallest to largest. Demonstrated in the program below:

 
with Ada.Text_IO; use Ada.Text_IO;
procedure Order is
 
type IntArray is array (Positive range <>) of Integer;
List1 : IntArray := (1, 2, 3, 4, 5);
List2 : IntArray := (1, 2, 1, 5, 2, 2);
List3 : IntArray := (1, 2, 1, 5, 2);
List4 : IntArray := (1, 2, 1, 5, 2);
 
type Animal is (Rat, Cat, Elephant);
type AnimalArray is array (Positive range <>) of Animal;
List5 : AnimalArray := (Cat, Elephant, Rat, Cat);
List6 : AnimalArray := (Cat, Elephant, Rat);
List7 : AnimalArray := (Cat, Cat, Elephant);
 
begin
Put_Line (Boolean'Image (List1 > List2)); -- True
Put_Line (Boolean'Image (List2 > List3)); -- True
Put_Line (Boolean'Image (List3 > List4)); -- False, equal
Put_Line (Boolean'Image (List5 > List6)); -- True
Put_Line (Boolean'Image (List6 > List7)); -- True
end Order;
 
Output:
TRUE
TRUE
FALSE
TRUE
TRUE


AppleScript[edit]

Translation of: JavaScript


<= is not defined over lists in AppleScript

-- <= for lists
-- compare :: [a] -> [a] -> Bool
on compare(xs, ys)
if length of xs = 0 then
true
else
if length of ys = 0 then
false
else
set {hx, txs} to uncons(xs)
set {hy, tys} to uncons(ys)
 
if hx = hy then
compare(txs, tys)
else
hx < hy
end if
end if
end if
end compare
 
 
 
-- TEST
on run
 
{compare([1, 2, 1, 3, 2], [1, 2, 0, 4, 4, 0, 0, 0]), ¬
compare([1, 2, 0, 4, 4, 0, 0, 0], [1, 2, 1, 3, 2])}
 
end run
 
 
---------------------------------------------------------------------------
 
-- GENERIC FUNCTION
 
-- uncons :: [a] -> Maybe (a, [a])
on uncons(xs)
if length of xs > 0 then
{item 1 of xs, rest of xs}
else
missing value
end if
end uncons
Output:
{false, true}

AutoHotkey[edit]

Works with: AutoHotkey_L

The function is overkill as we can just compare the list's ObjMaxIndex()

List1 := [1,2,1,3,2]
List2 := [1,2,0,4,4,0,0,0]
MsgBox % order(List1, List2)
 
order(L1, L2){
return L1.MaxIndex() < L2.MaxIndex()
}

AWK[edit]

 
# syntax: GAWK -f ORDER_TWO_NUMERICAL_LISTS.AWK
BEGIN {
split("1,2,1,5,2",list1,",")
split("1,2,1,5,2,2",list2,",")
split("1,2,3,4,5",list3,",")
split("1,2,3,4,5",list4,",")
x = compare_array(list1,list2) ? "<" : ">=" ; printf("list1%slist2\n",x)
x = compare_array(list2,list3) ? "<" : ">=" ; printf("list2%slist3\n",x)
x = compare_array(list3,list4) ? "<" : ">=" ; printf("list3%slist4\n",x)
exit(0)
}
function compare_array(arr1,arr2, ans,i) {
ans = 0
for (i=1; i<=length(arr1); i++) {
if (arr1[i] != arr2[i]) {
ans = 1
break
}
}
if (length(arr1) != length(arr2)) {
ans = 1
}
return(ans)
}
 
Output:
list1<list2
list2<list3
list3>=list4

BBC BASIC[edit]

'Ordered before' means 'less than' (see talk page).

      DIM list1(4) : list1() = 1, 2, 1, 5, 2
DIM list2(5) : list2() = 1, 2, 1, 5, 2, 2
DIM list3(4) : list3() = 1, 2, 3, 4, 5
DIM list4(4) : list4() = 1, 2, 3, 4, 5
 
IF FNorder(list1(), list2()) PRINT "list1<list2" ELSE PRINT "list1>=list2"
IF FNorder(list2(), list3()) PRINT "list2<list3" ELSE PRINT "list2>=list3"
IF FNorder(list3(), list4()) PRINT "list3<list4" ELSE PRINT "list3>=list4"
END
 
DEF FNorder(list1(), list2())
LOCAL i%, l1%, l2%
l1% = DIM(list1(),1) : l2% = DIM(list2(),1)
WHILE list1(i%) = list2(i%) AND i% < l1% AND i% < l2%
i% += 1
ENDWHILE
IF list1(i%) < list2(i%) THEN = TRUE
IF list1(i%) > list2(i%) THEN = FALSE
= l1% < l2%
Output:
list1<list2
list2<list3
list3>=list4

Bracmat[edit]

When evaluating a sum or a product, Bracmat creates an expression with a canonical order, which happens to be compatible with the order defined in this task. In a pattern, only a sum or product on the left hand side (lhs) of the match (:) operator is evaluated. In the solution below we match a composition of the two function arguments into a sum of two terms with itself. If the match expression succeeds, the lhs must already have been in canonical order before evaluation, which means that the first argument is smaller than the second argument. In that case the function outputs FALSE. Notice that if the arguments are the same, evaluation of the sum produces the product of one of the terms and a factor two. This complicates the pattern a bit.

(  1 2 3 4 5:?List1
& 1 2 1 5 2 2:?List2
& 1 2 1 5 2:?List3
& 1 2 1 5 2:?List4
& Cat Elephant Rat Cat:?List5
& Cat Elephant Rat:?List6
& Cat Cat Elephant:?List7
& ( gt
= first second
.  !arg:(?first,?second)
& out
$ ( (.!first)+(.!second)
 : ((.!first)+(.!second)|2*(.!first))
& FALSE
| TRUE
)
)
& gt$(!List1,!List2)
& gt$(!List2,!List3)
& gt$(!List3,!List4)
& gt$(!List4,!List5)
& gt$(!List5,!List6)
& gt$(!List6,!List7)
);
Output:
TRUE
TRUE
FALSE
FALSE
TRUE
TRUE

C[edit]

int list_cmp(int *a, int la, int *b, int lb)
{
int i, l = la;
if (l > lb) l = lb;
for (i = 0; i < l; i++) {
if (a[i] == b[i]) continue;
return (a[i] > b[i]) ? 1 : -1;
}
if (la == lb) return 0;
return la > lb ? 1 : -1;
}
This funciton returns one of three states, not a boolean. One can define boolean comparisons, such as list_less_or_eq, based on it:
#define list_less_or_eq(a,b,c,d) (list_cmp(a,b,c,d) != 1)

C#[edit]

namespace RosettaCode.OrderTwoNumericalLists
{
using System;
using System.Collections.Generic;
 
internal static class Program
{
private static bool IsLessThan(this IEnumerable<int> enumerable,
IEnumerable<int> otherEnumerable)
{
using (
IEnumerator<int> enumerator = enumerable.GetEnumerator(),
otherEnumerator = otherEnumerable.GetEnumerator())
{
while (true)
{
if (!otherEnumerator.MoveNext())
{
return false;
}
 
if (!enumerator.MoveNext())
{
return true;
}
 
if (enumerator.Current == otherEnumerator.Current)
{
continue;
}
 
return enumerator.Current < otherEnumerator.Current;
}
}
}
 
private static void Main()
{
Console.WriteLine(
new[] {1, 2, 1, 3, 2}.IsLessThan(new[] {1, 2, 0, 4, 4, 0, 0, 0}));
}
}
}
Output:
False

C++[edit]

The built-in comparison operators already do this:

#include <iostream>
#include <vector>
 
int main() {
std::vector<int> a;
a.push_back(1);
a.push_back(2);
a.push_back(1);
a.push_back(3);
a.push_back(2);
std::vector<int> b;
b.push_back(1);
b.push_back(2);
b.push_back(0);
b.push_back(4);
b.push_back(4);
b.push_back(0);
b.push_back(0);
b.push_back(0);
 
std::cout << std::boolalpha << (a < b) << std::endl; // prints "false"
return 0;
}

clojure[edit]

 
(defn lex? [a b]
(compare a b))
 

Common Lisp[edit]

(defun list< (a b)
(cond ((not b) nil)
((not a) t)
((= (first a) (first b))
(list< (rest a) (rest b)))
(t (< (first a) (first b)))))

Alternate version

(defun list< (a b)
(let ((x (find-if-not #'zerop (mapcar #'- a b))))
(if x (minusp x) (< (length a) (length b)))))

D[edit]

The built-in comparison operators already do this:

void main() {
assert([1,2,1,3,2] >= [1,2,0,4,4,0,0,0]);
}

Ela[edit]

[] <. _ = true
_ <. [] = false
(x::xs) <. (y::ys) | x == y = xs <. ys
| else = x < y
 
[1,2,1,3,2] <. [1,2,0,4,4,0,0,0]

Elixir[edit]

The built-in comparison functions already do this (not only for lists of numbers, but for any arbitrary data type).

iex(1)> [1,2,3] < [1,2,3,4]
true
iex(2)> [1,2,3] < [1,2,4]
true

Erlang[edit]

Builtin. Example use from Erlang shell:

 
5> [1,2,3] < [1,2,3,4].
true
6> [1,2,3] < [1,2,4].
true
 

F#[edit]

By using the Collection.Seq Module the static method Seq.compareWith fits our needs.

let inline cmp x y = if x < y then -1 else if x = y then 0 else 1
let before (s1 : seq<'a>) (s2 : seq<'a>) = (Seq.compareWith cmp s1 s2) < 0
 
[
([0], []);
([], []);
([], [0]);
([-1], [0]);
([0], [0]);
([0], [-1]);
([0], [0; -1]);
([0], [0; 0]);
([0], [0; 1]);
([0; -1], [0]);
([0; 0], [0]);
([0; 0], [1]);
]
|> List.iter (fun (x, y) -> printf "%A %s %A\n" x (if before x y then "< " else ">=") y)
Output:
[0] >= []
[] >= []
[] <  [0]
[-1] <  [0]
[0] >= [0]
[0] >= [-1]
[0] <  [0; -1]
[0] <  [0; 0]
[0] <  [0; 1]
[0; -1] >= [0]
[0; 0] >= [0]
[0; 0] <  [1]

Factor[edit]

All sequences respond to words in the math.order vocabulary.

IN: scratchpad { 2 3 } { 2 5 } before? .
t

Go[edit]

package main
 
import "fmt"
 
// If your numbers happen to be in the range of Unicode code points (0 to 0x10ffff), this function
// satisfies the task:
func lessRune(a, b []rune) bool {
return string(a) < string(b) // see also bytes.Compare
}
 
// Otherwise, the following function satisfies the task for all integer
// and floating point types, by changing the type definition appropriately.
type numericType int
 
func lessNT(a, b []numericType) bool {
l := len(a)
if len(b) < l {
l = len(b)
}
for i := 0; i < l; i++ {
if a[i] != b[i] {
return a[i] < b[i]
}
}
return l < len(b)
}
 
var testCases = [][][]numericType{
{{0}, {}},
{{}, {}},
{{}, {0}},
 
{{-1}, {0}},
{{0}, {0}},
{{0}, {-1}},
 
{{0}, {0, -1}},
{{0}, {0, 0}},
{{0}, {0, 1}},
{{0, -1}, {0}},
{{0, 0}, {0}},
{{0, 0}, {1}},
}
 
func main() {
// demonstrate the general function
for _, tc := range testCases {
fmt.Printf("order %6s before %6s : %t\n",
fmt.Sprintf("%v", tc[0]),
fmt.Sprintf("%v", tc[1]),
lessNT(tc[0], tc[1]))
}
fmt.Println()
 
// demonstrate that the byte specific function gives identical results
// by offsetting test data to a printable range of characters.
for _, tc := range testCases {
a := toByte(tc[0])
b := toByte(tc[1])
fmt.Printf("order %6q before %6q : %t\n",
string(a),
string(b),
lessByte(a, b))
}
}
 
func toByte(a []numericType) []byte {
b := make([]byte, len(a))
for i, n := range a {
b[i] = 'b' + byte(n)
}
return b
}
Output:
order    [0] before     [] : false
order     [] before     [] : false
order     [] before    [0] : true
order   [-1] before    [0] : true
order    [0] before    [0] : false
order    [0] before   [-1] : false
order    [0] before [0 -1] : true
order    [0] before  [0 0] : true
order    [0] before  [0 1] : true
order [0 -1] before    [0] : false
order  [0 0] before    [0] : false
order  [0 0] before    [1] : true

order    "b" before     "" : false
order     "" before     "" : false
order     "" before    "b" : true
order    "a" before    "b" : true
order    "b" before    "b" : false
order    "b" before    "a" : false
order    "b" before   "ba" : true
order    "b" before   "bb" : true
order    "b" before   "bc" : true
order   "ba" before    "b" : false
order   "bb" before    "b" : false
order   "bb" before    "c" : true

Groovy[edit]

Solution:

class CList extends ArrayList implements Comparable {
CList() { }
CList(Collection c) { super(c) }
int compareTo(Object that) {
assert that instanceof List
def n = [this.size(), that.size()].min()
def comp = [this[0..<n], that[0..<n]].transpose().find { it[0] != it[1] }
comp ? comp[0] <=> comp[1] : this.size() <=> that.size()
}
}

Test:

CList a, b; (a, b) = [[], []]; assert ! (a < b)
b = [1] as CList; assert (a < b)
a = [1] as CList; assert ! (a < b)
b = [2] as CList; assert (a < b)
a = [2, -1, 0] as CList; assert ! (a < b)
b = [2, -1] as CList; assert ! (a < b)
b = [2, -1, 0] as CList; assert ! (a < b)
b = [2, -1, 0, -17] as CList; assert (a < b)
a = [2, 8, 0] as CList; assert ! (a < b)

Haskell[edit]

The built-in comparison operators already do this:

Prelude>  [1,2,1,3,2] < [1,2,0,4,4,0,0,0]
False

Icon and Unicon[edit]

List_llt is written in the style of all Icon/Unicon relational operators returning its right argument if successful and signaling failure otherwise.

procedure main()
write( if list_llt([1,2,1,3,2],[1,2,0,4,4,0,0,0]) then "true" else "false" )
end
 
 
procedure list_llt(L1,L2) #: returns L2 if L1 lexically lt L2 or fails
every i := 1 to min(*L1,*L2) do
if L1[i] << L2[i] then return L2
else if L1[i] >> L2[i] then fail
if *L1 < *L2 then return L2
end

J[edit]

This is not a built-in in J.

before=: -.@(-: /:~)@,&<~

Example use:

    (,0) before ''
0
'' before ''
0
'' before ,0
1
(,_1) before ,0
1
(,0) before ,0
0
(,0) before ,_1
0
(,0) before 0 _1
1
(,0) before 0 0
1
(,0) before 0 1
1
0 _1 before ,0
0
0 0 before ,0
0
0 0 before ,1
1
 
(,'b') before ''
0
'' before ''
0
'' before ,'b'
1
(,'a') before ,'b'
1
(,'b') before ,'b'
0
(,'b') before ,'a'
0
(,'b') before 'ba'
1
(,'b') before 'bb'
1
(,'b') before 'bc'
1
'ba' before ,'b'
0
'bb' before ,'b'
0
'bb' before ,'c'
1

Java[edit]

Works with: Java version 1.5+
Translation of: Common Lisp

There are a few methods here. The method named "ordered" which works on arrays is a translation of Common Lisp. The other two are loose translations of Tcl (some tweaks were needed to get the length checks to work out) and are probably better options.

import java.util.Arrays;
import java.util.List;
 
public class ListOrder{
public static boolean ordered(double[] first, double[] second){
if(first.length == 0) return true;
if(second.length == 0) return false;
if(first[0] == second[0])
return ordered(Arrays.copyOfRange(first, 1, first.length),
Arrays.copyOfRange(second, 1, second.length));
return first[0] < second[0];
}
 
public static <T extends Comparable<? super T>> boolean ordered(List<T> first, List<T> second){
int i = 0;
for(; i < first.size() && i < second.size();i++){
int cmp = first.get(i).compareTo(second.get(i));
if(cmp == 0) continue;
if(cmp < 0) return true;
return false;
}
return i == first.size();
}
 
public static boolean ordered2(double[] first, double[] second){
int i = 0;
for(; i < first.length && i < second.length;i++){
if(first[i] == second[i]) continue;
if(first[i] < second[i]) return true;
return false;
}
return i == first.length;
}
}

JavaScript[edit]

ES6[edit]

<= is already defined for numeric lists in JavaScript

(() => {
'use strict';
 
// <= is already defined for lists in JS
 
// compare :: [a] -> [a] -> Bool
const compare = (xs, ys) => xs <= ys;
 
 
// TEST
return [
compare([1, 2, 1, 3, 2], [1, 2, 0, 4, 4, 0, 0, 0]),
compare([1, 2, 0, 4, 4, 0, 0, 0], [1, 2, 1, 3, 2])
];
 
// --> [false, true]
})()
 
Output:
[false, true]

Joy[edit]

 
DEFINE order ==
[equal] [false]
[[[[size] dip size <=] [[<=] mapr2 true [and] fold]] [i] map i and]
ifte.
 

Using it:

[1 2] [1 2 3] order. # true
[1 2] [1 3] order.   # true
[1 2] [1 2] order.   # false
[1 3] [1 2] order.   # false
[1 2 3] [1 2] order. # false

jq[edit]

jq's builtin comparison operators use lexicographic ordering for arrays in general, not just arrays of integers.
 
[1,2,3] < [1,2,3,4] # => true
[1,2,3] < [1,2,4] # => true
[1,2,3] < [1,2,3] # => false

Julia[edit]

islexfirst is a somewhat permissive function in that it will accept many sorts of lists for comparison. It does check that all of the elements of both input lists are of some real number type, and if not will throw a DomainError.

Functions

 
function isallreal{T<:AbstractArray}(a::T)
all(map(x->isa(x, Real), a))
end
 
function islexfirst{T<:AbstractArray,U<:AbstractArray}(a::T, b::U)
isallreal(a) && isallreal(b) || throw(DomainError())
for i in 1:min(length(a), length(b))
x = a[i]
y = b[i]
x != y || continue
return x < y
end
return length(a) < length(b)
end
 

Main

 
tests = {[1, 2, 3],
primes(10),
0:2:6,
[-Inf, 0.0, Inf],
[π, e, φ, catalan],
[2015, 5],
[-sqrt(50.0), 50.0^2],
}
 
println("Testing islexfirst:")
for (a, b) in combinations(tests, 2)
tres = islexfirst(a, b) ? " is " : " is not "
tres *= "lexically prior to\n "
println("\n ", a, tres, b)
end
 
Output:
Testing islexfirst:

    [1,2,3] is lexically prior to
    [2,3,5,7]

    [1,2,3] is not lexically prior to
    0:2:6

    [1,2,3] is not lexically prior to
    [-Inf,0.0,Inf]

    [1,2,3] is lexically prior to
    [3.141592653589793,2.718281828459045,1.618033988749895,0.915965594177219]

    [1,2,3] is lexically prior to
    [2015,5]

    [1,2,3] is not lexically prior to
    [-7.0710678118654755,2500.0]

    [2,3,5,7] is not lexically prior to
    0:2:6

    [2,3,5,7] is not lexically prior to
    [-Inf,0.0,Inf]

    [2,3,5,7] is lexically prior to
    [3.141592653589793,2.718281828459045,1.618033988749895,0.915965594177219]

    [2,3,5,7] is lexically prior to
    [2015,5]

    [2,3,5,7] is not lexically prior to
    [-7.0710678118654755,2500.0]

    0:2:6 is not lexically prior to
    [-Inf,0.0,Inf]

    0:2:6 is lexically prior to
    [3.141592653589793,2.718281828459045,1.618033988749895,0.915965594177219]

    0:2:6 is lexically prior to
    [2015,5]

    0:2:6 is not lexically prior to
    [-7.0710678118654755,2500.0]

    [-Inf,0.0,Inf] is lexically prior to
    [3.141592653589793,2.718281828459045,1.618033988749895,0.915965594177219]

    [-Inf,0.0,Inf] is lexically prior to
    [2015,5]

    [-Inf,0.0,Inf] is lexically prior to
    [-7.0710678118654755,2500.0]

    [3.141592653589793,2.718281828459045,1.618033988749895,0.915965594177219] is lexically prior to
    [2015,5]

    [3.141592653589793,2.718281828459045,1.618033988749895,0.915965594177219] is not lexically prior to
    [-7.0710678118654755,2500.0]

    [2015,5] is not lexically prior to
    [-7.0710678118654755,2500.0]

Kotlin[edit]

// version 1.0.6
 
operator fun <T> List<T>.compareTo(other: List<T>): Int
where T: Comparable<T>, T: Number {
for (i in 0 until this.size) {
if (other.size == i) return 1
when {
this[i] < other[i] -> return -1
this[i] > other[i] -> return 1
}
}
return if (this.size == other.size) 0 else -1
}
 
fun main(args: Array<String>) {
val lists = listOf(
listOf(1, 2, 3, 4, 5),
listOf(1, 2, 1, 5, 2, 2),
listOf(1, 2, 1, 5, 2),
listOf(1, 2, 1, 5, 2),
listOf(1, 2, 1, 3, 2),
listOf(1, 2, 0, 4, 4, 0, 0, 0),
listOf(1, 2, 0, 4, 4, 1, 0, 0)
)
for (i in 0 until lists.size) println("list${i + 1} : ${lists[i]}")
println()
for (i in 0 until lists.size - 1) println("list${i + 1} > list${i + 2} = ${lists[i] > lists[i + 1]}")
}
Output:
list1 : [1, 2, 3, 4, 5]
list2 : [1, 2, 1, 5, 2, 2]
list3 : [1, 2, 1, 5, 2]
list4 : [1, 2, 1, 5, 2]
list5 : [1, 2, 1, 3, 2]
list6 : [1, 2, 0, 4, 4, 0, 0, 0]
list7 : [1, 2, 0, 4, 4, 1, 0, 0]

list1 > list2 = true
list2 > list3 = true
list3 > list4 = false
list4 > list5 = true
list5 > list6 = true
list6 > list7 = false

LabVIEW[edit]

Translation of: AutoHotkey

This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.
LabVIEW Order two numerical lists.png

Lasso[edit]

This is built into the Lasso comparison operators

local(
first = array(1,2,1,3,2),
second = array(1,2,0,4,4,0,0,0),
)
#first < #second
 
local(
first = array(1,1,1,3,2),
second = array(1,2,0,4,4,0,0,0),
)
#first < #second
Output:
false
true

Lhogho[edit]

Uses standard '=' notation

print [1 2] = [1 2]
print [1 2] = [1 2 3]
print [1 3] = [1 2]
print [1 2 3] = [1 2]
 
make "list1 [1 2 3 4 5 6]
make "list2 [1 2 3 4 5 7]
print :list1 = :list2
Output:
true 
false
false
false
false

Lua[edit]

In Lua tables with numerical indices are used as lists or arrays and they do not support comparison out-of-the-box, so a function is needed to implement the comparison:

function arraycompare(a, b)
for i = 1, #a do
if b[i] == nil then
return true
end
if a[i] ~= b[i] then
return a[i] < b[1]
end
end
return true
end

Here is some demonstration code:

function randomarray()
local t = {}
for i = 1, math.random(1, 10) do
t[i] = math.random(1, 10)
end
return t
end
 
math.randomseed(os.time())
 
for i = 1, 10 do
local a = randomarray()
local b = randomarray()
 
print(
string.format("{%s} %s {%s}",
table.concat(a, ', '),
arraycompare(a, b) and "<=" or ">",
table.concat(b, ', ')))
end
Output:
(time used as random seed: 1413127434):
    {10, 7, 4, 9, 10, 3, 5, 5, 5, 5} > {7, 4, 6, 4, 3, 5, 10}
    {5, 7} <= {6, 3, 7, 7, 7, 1}
    {4} <= {10, 10, 3, 8, 10, 5, 2, 5, 10, 6}
    {6} <= {6, 10, 2, 1, 9, 4, 5, 6, 9}
    {9, 5, 7, 5, 5, 7, 9, 5, 6, 8} > {4, 7, 3, 5, 1, 2, 1, 2}
    {10, 8, 6, 1, 8, 5, 4} > {1, 2}
    {9, 7} > {4, 1, 5, 2, 6, 1, 9, 3, 5}
    {5, 9, 7, 6, 10, 8} <= {9, 6, 9}
    {4, 3, 4, 6, 3, 6, 7, 2, 2, 5} > {3, 10, 6, 8, 1}
    {1, 5, 1, 5, 4} > {1, 3, 5, 3, 2, 10, 1}

Mathematica[edit]

 
order[List1_, List2_] := With[{
L1 = List1[[1 ;; Min @@ Length /@ {List1, List2}]],
L2 = List2[[1 ;; Min @@ Length /@ {List1, List2}]]
},
If [Thread[Order[L1, L2]] == 0,
Length[List1] < Length[List2],
Thread[Order[L1, L2]] == 1
]]
Example use:
order[ {1, 2, 1, 3, 2}, {1, 2, 0, 4, 4, 0, 0, 0} ]
->False

order[ {1, 2}, {1, 2, 4, 4, 0, 0} ]
->True

Maxima[edit]

"<<"(a,b):=block([n:min(length(a),length(b))],
catch(for i thru n do (if a[i]#b[i] then throw(is(a[i]<b[i]))),
throw(is(length(a)<length(b)))))$
infix("<<")$
 
[1,2,3] << [1,2,4];
true
 
[1,2,3] << [1,2];
false
 
[1,2] << [1,2];
false

Mercury[edit]

For a particular numerical type, you can get away with

:- pred lt(list(int)::in, list(int)::in) is semidet.
lt([], [_|_]).
lt([H1|T1], [H2|T2]) :- H1 =< H2, T1 `lt` T2.

For a list of any numerical type, one way would be to use a typeclass:

:- pred lt(list(T)::in, list(T)::in) is semidet <= comparable(T).
lt([], [_|_]).
lt([H1|T1], [H2|T2]) :- H1 =< H2, T1 `lt` T2.

... which you would have to create:

:- module comparable.
:- interface.
:- import_module int, float, integer, list.
 
:- typeclass comparable(T) where [
pred '<'(T::in, T::in) is semidet,
pred '=<'(T::in, T::in) is semidet
].
:- instance comparable(int).
:- instance comparable(float).
:- instance comparable(integer).
:- instance comparable(list(T)) <= comparable(T).
 
:- implementation.
 
:- instance comparable(int) where [
pred('<'/2) is int.(<),
pred('=<'/2) is int.(=<)
].
% likewise for float and integer...
:- instance comparable(list(T)) <= comparable(T) where [
pred('<'/2) is lt,  % the 'lt' above.
pred('=<'/2) is lte  % 'lt' with: lte([], []).
].
 
% pred lt
% pred lte

Which would be used in this way - note the typeclass and the comparison operator.

:- pred test(list(T), list(T), io, io) <= comparable(T).
:- mode test(in, in, di, uo) is det.
test(A, B) -->
io.write(A), io.write_string(" < "), io.write(B),
io.write_string(" : "), io.write_string(S), io.nl,
{ A < B -> S = "yes" ; S = "no" }.

Nim[edit]

proc `<`[T](a, b: openarray[T]): bool =
for i in 0 .. min(a.len, b.len):
if a[i] < b[i]: return true
if a[i] > b[i]: return false
return a.len < b.len
 
echo([1,2,1,3,2] < [1,2,0,4,4,0,0,0])
Output:
false

OCaml[edit]

The built-in comparison operators already do this for lists (although this is not documented):

# [1;2;1;3;2] < [1;2;0;4;4;0;0;0];;
- : bool = false

(Warning: However, the built-in comparison operators do not do this for arrays:

# [|1;2;1;3;2|] < [|1;2;0;4;4;0;0;0|];;
- : bool = true

)

But we could write it explicitly this way:

let rec ordered_lists = function
| x1::tl1, x2::tl2 ->
(match compare x1 x2 with
| 0 -> ordered_lists (tl1, tl2)
| 1 -> false
| _ -> true)
| [], _ -> true
| _ -> false

Here is a small script to test this function:

(* copy-paste the code of ordered_lists here *)
 
let make_num_list p n =
let rec aux acc =
if Random.int p = 0 then acc
else aux (Random.int n :: acc)
in
aux []
 
let print_num_list lst =
List.iter (Printf.printf " %d") lst;
print_newline()
 
let () =
Random.self_init();
let lst1 = make_num_list 8 5 in
let lst2 = make_num_list 8 5 in
print_num_list lst1;
print_num_list lst2;
Printf.printf "ordered: %B\n" (ordered_lists (lst1, lst2))

Sample execution:

$ ocaml ordered_lists.ml
 1 2 1 3 2
 1 2 0 4 4 0 0 0
ordered: false

Also notice that the function ordered_lists will work with anything the function Pervasives.compare is able to compare (most OCaml types and structures made from the base types). In the prototype of this function below 'a list means a list of anything:

val ordered_lists : 'a list * 'a list -> bool

Oforth[edit]

In Oforth, list comparison is already defined.

Output:
[1,2,0,4,4,0,0,0] [1,2,1,3,2] <= .
1 ok

PARI/GP[edit]

lex(u,v)<1

Perl[edit]

use strict;
use warnings;
 
sub orderlists {
my ($firstlist, $secondlist) = @_;
 
my ($first, $second);
while (@{$firstlist}) {
$first = shift @{$firstlist};
if (@{$secondlist}) {
$second = shift @{$secondlist};
if ($first < $second) {
return 1;
}
if ($first > $second) {
return 0;
}
}
else {
return 0;
}
}
 
@{$secondlist} ? 1 : 0;
}
 
foreach my $pair (
[[1, 2, 4], [1, 2, 4]],
[[1, 2, 4], [1, 2, ]],
[[1, 2, ], [1, 2, 4]],
[[55,53,1], [55,62,83]],
[[20,40,51],[20,17,78,34]],
) {
my $first = $pair->[0];
my $second = $pair->[1];
my $before = orderlists([@$first], [@$second]) ? 'true' : 'false';
print "(@$first) comes before (@$second) : $before\n";
}
Output:
(1 2 4) comes before (1 2 4) : false
(1 2 4) comes before (1 2) : false
(1 2) comes before (1 2 4) : true
(55 53 1) comes before (55 62 83) : true
(20 40 51) comes before (20 17 78 34) : false

Perl 6[edit]

There is already a built-in comparison operator.

my @a = <1 2 4>;
my @b = <1 2 4>;
say @a," before ",@b," = ", @a before @b;
 
@a = <1 2 4>;
@b = <1 2>;
say @a," before ",@b," = ", @a before @b;
 
@a = <1 2>;
@b = <1 2 4>;
say @a," before ",@b," = ", @a before @b;
 
for 1..10 {
my @a = flat (^100).roll((2..3).pick);
my @b = flat @a.map: { Bool.pick ?? $_ !! (^100).roll((0..2).pick) }
say @a," before ",@b," = ", @a before @b;
}
Output:
1 2 4 before 1 2 4 = False
1 2 4 before 1 2 = False
1 2 before 1 2 4 = True
63 52 before 0 52 = False
17 75 24 before 31 75 24 = True
43 32 before 43 32 = False
73 84 before 2 84 = False
73 92 before 40 24 46 = False
16 24 before 41 24 = True
9 12 22 before 9 12 32 67 = True
81 23 before 81 23 = False
55 53 1 before 55 62 83 = True
20 40 51 before 20 17 78 34 = False

Phix[edit]

Handled natively, eg ("?" is the shorthand print operator)

?{1,2,3}<{1,2,3,4}  -- 1
?{1,2,3,4}<{1,2,3} -- 0
?{1,2,4}<{1,2,3} -- 0
?{1,2,3}<{1,2,3} -- 0
?{1,2,3}<{1,2,4} -- 1

Elements can be any mix of integers, floating point numbers, strings, or nested subsequences, with atoms ordered before sequences.
If you want -1/0/+1 (instead of the true(1)/false(0) shown above), use the builtin compare() function.

PicoLisp[edit]

The built-in comparison functions already do this (not only for lists of numbers, but for any arbitrary data type).

: (> (1 2 0 4 4 0 0 0) (1 2 1 3 2))
-> NIL

Pike[edit]

int(0..1) order_array(array a, array b)
{
if (!sizeof(a)) return true;
if (!sizeof(b)) return false;
if (a[0] == b[0])
return order_array(a[1..], b[1..]);
return a[0] < b[0];
}

Pikes Array.sort_array() function can sort an array of arrays using the < operator, but it will sort longer arrays before shorter ones. Therefore the above function is still needed if the intent is to use the comparison for a sort operation.

If the numbers are in 32bit signed integer range, the following works too:

(string)a < (string)b;

PL/I[edit]

lists: procedure options (main);  /* 8 June 2014 */
 
declare a(10) fixed initial (1, 2, 3, 4, 5, 8, 9, 10, 16, 17),
b(15) fixed initial (5, 6, 7, 8, 9, 10, 11, 12, 15, 16, 17, 18, 20, 22, 23);
 
put skip list (compare(a, b));
put skip list (compare(b, a));
put skip list (compare(a, a));
 
 
compare: procedure (a, b) returns (bit (1));
declare (a, b)(*) fixed;
declare (i, m, n) fixed binary;
 
m = hbound(a,1); n = hbound(b,1);
do i = 1 to min(m, n);
return (a(i) < b(i));
end;
return (m < n);
end compare;
 
end lists;

Results:

'1'B    (true)
'0'B    (false)
'0'B

PowerShell[edit]

 
function order($as,$bs) {
if($as -and $bs) {
$a, $as = $as
$b, $bs = $bs
if($a -eq $b) {order $as $bs}
else{$a -lt $b}
} elseif ($bs) {$true} else {$false}
}
"$(order @(1,2,1,3,2) @(1,2,0,4,4,0,0,0))"
 

Output:

False

Non-Recursive Version[edit]

 
function Test-Order ([int[]]$ReferenceArray, [int[]]$DifferenceArray)
{
for ($i = 0; $i -lt $ReferenceArray.Count; $i++)
{
if ($ReferenceArray[$i] -lt $DifferenceArray[$i])
{
return $true
}
elseif ($ReferenceArray[$i] -gt $DifferenceArray[$i])
{
return $false
}
}
 
return ($ReferenceArray.Count -lt $DifferenceArray.Count) -or (Compare-Object $ReferenceArray $DifferenceArray) -eq $null
}
 
 
Test-Order -ReferenceArray 1, 2, 1, 3, 2 -DifferenceArray 1, 2, 0, 4, 4, 0, 0, 0
Test-Order -ReferenceArray 1, 2, 1, 3, 2 -DifferenceArray 1, 2, 2, 4, 4, 0, 0, 0
Test-Order -ReferenceArray 1, 2, 3 -DifferenceArray 1, 2
Test-Order -ReferenceArray 1, 2 -DifferenceArray 1, 2, 3
Test-Order -ReferenceArray 1, 2 -DifferenceArray 1, 2
 
Output:
False
True
False
True
True

PureBasic[edit]

DataSection
Array_1:
Data.i 5 ;element count
Data.i 1, 2, 3, 4, 5 ;element data
Array_2:
Data.i 6
Data.i 1, 2, 1, 5, 2, 2
Array_3:
Data.i 5
Data.i 1, 2, 1, 5, 2
Array_4:
Data.i 5
Data.i 1, 2, 1, 5, 2
Array_5:
Data.i 4
Data.i 1, 2, 1, 6
Array_6:
Data.i 5
Data.i 1, 2, 1, 6, 2
EndDataSection
 
#False = 0
#True = 1
 
;helper subrountine to initialize a dataset, *dataPtr points to the elementcount followed by the element data
Procedure initArrayData(Array a(1), *dataPtr)
Protected elementCount = PeekI(*dataPtr)
 
Dim a(elementCount - 1)
For i = 0 To elementCount - 1
*dataPtr + SizeOf(Integer)
a(i) = PeekI(*dataPtr)
Next
EndProcedure
 
;helper subroutine that returns 'True' or 'False' for a boolean input
Procedure.s booleanText(b)
If b: ProcedureReturn "True": EndIf
ProcedureReturn "False"
EndProcedure
 
Procedure order(Array a(1), Array b(1))
Protected len_a = ArraySize(a()), len_b = ArraySize(b()), elementIndex
 
While elementIndex <= len_a And elementIndex <= len_b And a(elementIndex) = b(elementIndex)
elementIndex + 1
Wend
 
If (elementIndex > len_a And elementIndex <= len_b) Or (elementIndex <= len_b And a(elementIndex) <= b(elementIndex))
ProcedureReturn #True
EndIf
EndProcedure
 
Dim A_1(0): initArrayData(A_1(), ?Array_1)
Dim A_2(0): initArrayData(A_2(), ?Array_2)
Dim A_3(0): initArrayData(A_3(), ?Array_3)
Dim A_4(0): initArrayData(A_4(), ?Array_4)
Dim A_5(0): initArrayData(A_5(), ?Array_5)
Dim A_6(0): initArrayData(A_6(), ?Array_6)
 
If OpenConsole()
PrintN(booleanText(order(A_1(), A_2()))) ;False
PrintN(booleanText(order(A_2(), A_3()))) ;False
PrintN(booleanText(order(A_3(), A_4()))) ;False
PrintN(booleanText(order(A_4(), A_5()))) ;True
PrintN(booleanText(order(A_5(), A_6()))) ;True
 
Print(#crlf$ + #crlf$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf
 
Output:
False
False
False
True
True

Python[edit]

The built-in comparison operators already do this:

>>> [1,2,1,3,2] < [1,2,0,4,4,0,0,0]
False

Racket[edit]

#lang racket
 
(define (lex<? a b)
(cond ((null? b) #f)
((null? a) #t)
((= (car a) (car b)) (lex<? (cdr a) (cdr b)))
(else (< (car a) (car b)))))
 
(lex<? '(1 2 3 4 5) '(1 2 3 4 4)) ; -> #f
 

Rascal[edit]

The built-in comparison operator already does this:

rascal>[2,1,3] < [5,2,1,3]
bool: true

REXX[edit]

This REXX example uses the same lists as     BBC BASIC.
This example will also work with non-numeric strings.

/*REXX pgm determines if a list < previous list,  & returns true | false*/
@. =
@.1 = 1 2 1 5 2
@.2 = 1 2 1 5 2 2
@.3 = 1 2 3 4 5
@.4 = 1 2 3 4 5 /* [↓] compare list to previous.*/
do j=2 while @.j\==''; p=j-1 /*P is the previous.*/
answer=FNorder(@.p, @.j) /*obtain the answer.*/
if answer=='true' then is= ' < ' /*convert from true */
else is= ' ≥ ' /*convert from false*/
say right('['@.p"]", 40) is '['@.j"]"; say
end /*i*/ /* [↑] display (+ a blank line)*/
exit /*stick a fork in it, we're done.*/
/*──────────────────────────────────FNORDER subroutine──────────────────*/
FNorder: procedure; parse arg x,y; wx=words(x); wy=words(y)
 
do k=1 for min(wx,wy)
a=word(x,k); b=word(y,k)
if a<b then return 'true'
else if a>b then return 'false'
end /*k*/
if wx<wy then return 'true'
return 'false'
Output:
                             [1 2 1 5 2]  <  [1 2 1 5 2 2]

                           [1 2 1 5 2 2]  <  [1 2 3 4 5]

                             [1 2 3 4 5]  ≥  [1 2 3 4 5]

Ring[edit]

 
list1 = "1, 2, 1, 5, 2"
list2 = "5, 2, 1, 5, 2, 2"
list3 = "1, 2, 3, 4, 5"
list4 = "1, 2, 3, 4, 5"
 
if order(list1, list2) = 0 see "list1=list2" + nl
but order(list1, list2) < 0 see "list1<list2" + nl
else see "list1>list2" + nl ok
 
if order(list2, list3) = 0 see "list2=list3" + nl
but order(list2, list3) < 0 see "list2<list3" + nl
else see "list2>list3" + nl ok
 
if order(list3, list4) = 0 see "list3=list4" + nl
but order(list3, list4) < 0 see "list3<list4" + nl
else see "list3>list4" + nl ok
 
func order alist, blist
return strcmp(alist, blist)
 

Output:

list1<list2
list2>list3
list3=list4

Ruby[edit]

The built-in <=> operator already does this:

>> ([1,2,1,3,2] <=> [1,2,0,4,4,0,0,0]) < 0
=> false

Scala[edit]

def lessThan1(a: List[Int], b: List[Int]): Boolean =
if (b.isEmpty) false
else if (a.isEmpty) true
else if (a.head != b.head) a.head < b.head
else lessThan1(a.tail, b.tail)
def lessThan2(a: List[Int], b: List[Int]): Boolean = (a, b) match {
case (_, Nil) => false
case (Nil, _) => true
case (a :: _, b :: _) if a != b => a < b
case _ => lessThan2(a.tail, b.tail)
}
def lessThan3(a: List[Int], b: List[Int]): Boolean =
a.zipAll(b, Integer.MIN_VALUE, Integer.MIN_VALUE)
.find{case (a, b) => a != b}
.map{case (a, b) => a < b}
.getOrElse(false)
val tests = List(
(List(1, 2, 3), List(1, 2, 3)) -> false,
(List(3, 2, 1), List(3, 2, 1)) -> false,
(List(1, 2, 3), List(3, 2, 1)) -> true,
(List(3, 2, 1), List(1, 2, 3)) -> false,
(List(1, 2), List(1, 2, 3)) -> true,
(List(1, 2, 3), List(1, 2)) -> false
)
 
tests.foreach{case test @ ((a, b), c) =>
assert(lessThan1(a, b) == c, test)
assert(lessThan2(a, b) == c, test)
assert(lessThan3(a, b) == c, test)
}

Scheme[edit]

(define (lex<? a b)
(cond ((null? b) #f)
((null? a) #t)
((= (car a) (car b)) (lex<? (cdr a) (cdr b)))
(else (< (car a) (car b)))))

Seed7[edit]

The operator corresponding to the ordering described in this example is less than.

$ include "seed7_05.s7i";
 
const proc: main is func
begin
writeln([] (1) < [] (1, 2)); # If the first list runs out of elements the result is TRUE.
writeln([] (1, 2) < [] (1)); # If the second list runs out of elements the result is FALSE.
writeln([] (1, 2) < [] (1, 2)); # If both lists run out of elements the result is FALSE.
writeln([] (1, 2, 3) < [] (1, 1, 3)); # The second element is greater than --> FALSE
writeln([] (1, 2, 3) < [] (1, 3, 3)); # The second element is less than --> TRUE
writeln(0 times 0 < [] (1)); # The empty list is less than any nonempty list --> TRUE
writeln([] (1) < 0 times 0); # Any nonempty list is not less than the empty list --> FALSE
writeln(0 times 0 < 0 times 0); # The empty list is not less than the empty list --> FALSE
end func;
Output:
TRUE
FALSE
FALSE
FALSE
TRUE
TRUE
FALSE
FALSE

Sidef[edit]

Built-in, via the comparison operator (`<=>`):

func ordered(a, b) {
(a <=> b) < 0
}
 
for p in [
Pair([1,2,4], [1,2,4]),
Pair([1,2,4], [1,2] ),
Pair([1,2], [1,2,4]),
] {
var a = p.first
var b = p.second
var before = ordered(a, b)
say "#{a} comes before #{b} : #{before}"
}
Output:
[1, 2, 4] comes before [1, 2, 4] : false
[1, 2, 4] comes before [1, 2] : false
[1, 2] comes before [1, 2, 4] : true

Standard ML[edit]

- List.collate Int.compare ([1,2,1,3,2], [1,2,0,4,4,0,0,0]) = LESS;
val it = false : bool

Swift[edit]

let a = [1,2,1,3,2]
let b = [1,2,0,4,4,0,0,0]
println(lexicographicalCompare(a, b)) // this is "less than"
Output:
false

Tcl[edit]

proc numlist< {A B} {
foreach a $A b $B {
if {$a<$b} {
return 1
} elseif {$a>$b} {
return 0
}
}
return 0
}

TUSCRIPT[edit]

 
$$ MODE TUSCRIPT
MODE DATA
$$ numlists=*
1'2'1'3'2
1'2'0'4'4'0'0'0
1'2'3'4'5
1'2'1'5'2'2
1'2'1'6
1'2'1'6'2
1'2'4
1'2'4
1'2
1'2'4
$$ MODE TUSCRIPT
list1="1'2'5'6'7"
LOOP n,list2=numlists
text=CONCAT (" ",list1," < ",list2)
IF (list1<list2) THEN
PRINT " true: ",text
ELSE
PRINT "false: ",text
ENDIF
list1=VALUE(list2)
ENDLOOP
 
Output:
false:  1'2'5'6'7 < 1'2'1'3'2
false:  1'2'1'3'2 < 1'2'0'4'4'0'0'0
 true:  1'2'0'4'4'0'0'0 < 1'2'3'4'5
false:  1'2'3'4'5 < 1'2'1'5'2'2
 true:  1'2'1'5'2'2 < 1'2'1'6
 true:  1'2'1'6 < 1'2'1'6'2
 true:  1'2'1'6'2 < 1'2'4
false:  1'2'4 < 1'2'4
false:  1'2'4 < 1'2
 true:  1'2 < 1'2'4 

VBScript[edit]

 
Function order_list(arr1,arr2)
order_list = "FAIL"
n1 = UBound(arr1): n2 = UBound(arr2)
n = 0 : p = 0
If n1 > n2 Then
max = n2
Else
max = n1
End If
For i = 0 To max
If arr1(i) > arr2(i) Then
n = n + 1
ElseIf arr1(i) = arr2(i) Then
p = p + 1
End If
Next
If (n1 < n2 And n = 0) Or _
(n1 = n2 And n = 0 And p - 1 <> n1) Or _
(n1 > n2 And n = 0 And p = n2) Then
order_list = "PASS"
End If
End Function
 
WScript.StdOut.WriteLine order_list(Array(-1),Array(0))
WScript.StdOut.WriteLine order_list(Array(0),Array(0))
WScript.StdOut.WriteLine order_list(Array(0),Array(-1))
WScript.StdOut.WriteLine order_list(Array(0),Array(0,-1))
WScript.StdOut.WriteLine order_list(Array(0),Array(0,0))
WScript.StdOut.WriteLine order_list(Array(0),Array(0,1))
WScript.StdOut.WriteLine order_list(Array(0,-1),Array(0))
WScript.StdOut.WriteLine order_list(Array(0,0),Array(0))
WScript.StdOut.WriteLine order_list(Array(0,0),Array(1))
WScript.StdOut.WriteLine order_list(Array(1,2,1,3,2),Array(1,2,0,4,4,0,0,0))
 
Output:
PASS
FAIL
FAIL
PASS
PASS
PASS
FAIL
FAIL
PASS
FAIL

Wart[edit]

We'll simply overload < for lists.

def (a < b) :case (or list?.a list?.b)
if not.b
nil
not.a
b
(car.a = car.b)
(cdr.a < cdr.b)
 :else
(car.a < car.b)
Output:
(< '(1 2 3) '(1 2 4))
=> 4
(< '(1 2 4) '(1 2 3))
=> nil

(< '(1 2 3) '(1 2 3 4))
=> (4)
(< '(1 2 4) '(1 2 3 4))
=> nil

zkl[edit]

fcn listLT(a,b){
a.walker().zip(b).filter1(fcn([(a,b)]){ a<b }) : // lazy
if(_) return(True);;
a.len()<b.len()
}
Output:
listLT(T(1,2,3),T(2,3,4)).println();   //-->True
listLT(T(2,3,4),T(1,2,3)).println();   //-->False
listLT(T(1,2),T(1,2,3,4)).println();   //-->True
listLT(T(1,2,3,4),T(1,2,3)).println(); //-->False
listLT(T(1,2,3),T(1,2,3)).println();   //-->False