Order two numerical lists: Difference between revisions

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Though most modern languages have sorting functionality built in, programmers sometimes find it necessary to write their own sorts.

Usually this is just an instructional activity.

Below are some sorting algorithms that have been implemented on Rosetta Code.

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.

11l

Translation of: Python

AArch64 Assembly

Works with: as version Raspberry Pi 3B version Buster 64 bits

<lang AArch64 Assembly> /* ARM assembly AARCH64 Raspberry PI 3B */ /* program orderlist64.s */

/*******************************************/ /* Constantes file */ /*******************************************/ /* for this file see task include a file in language AArch64 assembly*/ .include "../includeConstantesARM64.inc"

/*********************************/ /* Initialized data */ /*********************************/ .data szMessResult1: .asciz "List1 < List2 \n" // message result szMessResult2: .asciz "List1 => List2 \n" // message result szCarriageReturn: .asciz "\n"

qTabList1: .quad 1,2,3,4,5 .equ NBELEMENTS1, (. - qTabList1) /8 qTabList2: .quad 1,2,1,5,2,2 .equ NBELEMENTS2, (. - qTabList2) /8 qTabList3: .quad 1,2,3,4,5 .equ NBELEMENTS3, (. - qTabList3) /8 qTabList4: .quad 1,2,3,4,5,6 .equ NBELEMENTS4, (. - qTabList4) /8 /*********************************/ /* UnInitialized data */ /*********************************/ .bss /*********************************/ /* code section */ /*********************************/ .text .global main main: // entry of program

   ldr x0,qAdriTabList1
   mov x1,NBELEMENTS1
   ldr x2,qAdriTabList2
   mov x3,NBELEMENTS2
   bl listeOrder
   cmp x0,0                                // false ?
   beq 1f                                  // yes
   ldr x0,qAdrszMessResult1                // list 1 < list 2
   bl affichageMess                        // display message
   b 2f

1:

   ldr x0,qAdrszMessResult2
   bl affichageMess                        // display message

2:

   ldr x0,qAdriTabList1
   mov x1,NBELEMENTS1
   ldr x2,qAdriTabList3
   mov x3,NBELEMENTS3
   bl listeOrder
   cmp x0,0                               // false ?
   beq 3f                                  // yes
   ldr x0,qAdrszMessResult1                // list 1 < list 2
   bl affichageMess                        // display message
   b 4f

3:

   ldr x0,qAdrszMessResult2
   bl affichageMess                        // display message

4:

   ldr x0,qAdriTabList1
   mov x1,NBELEMENTS1
   ldr x2,qAdriTabList4
   mov x3,NBELEMENTS4
   bl listeOrder
   cmp x0,0                               // false ?
   beq 5f                                  // yes
   ldr x0,qAdrszMessResult1                // list 1 < list 2
   bl affichageMess                        // display message
   b 6f

5:

   ldr x0,qAdrszMessResult2
   bl affichageMess                        // display message

6: 100: // standard end of the program

   mov x0,0                              // return code
   mov x8,EXIT                           // request to exit program
   svc 0                                  // perform the system call

qAdriTabList1: .quad qTabList1 qAdriTabList2: .quad qTabList2 qAdriTabList3: .quad qTabList3 qAdriTabList4: .quad qTabList4 qAdrszMessResult1: .quad szMessResult1 qAdrszMessResult2: .quad szMessResult2 qAdrszCarriageReturn: .quad szCarriageReturn /******************************************************************/ /* liste order */ /******************************************************************/ /* x0 contains the address of list 1 */ /* x1 contains list 1 size */ /* x2 contains the address of list 2 */ /* x3 contains list 2 size */ /* x0 returns 1 if list1 < list2 */ /* x0 returns 0 else */ listeOrder:

   stp x1,lr,[sp,-16]!          // save  registers
   stp x2,x3,[sp,-16]!          // save  registers
   cbz x1,99f                    // list 1 size = zero ?
   cbz x3,98f                    // list 2 size = zero ?

   mov x4,#0                    // index list 1
   mov x5,#0                    // index list 2

1:

   ldr x6,[x0,x4,lsl #3]        // load list 1 element
   ldr x8,[x2,x5,lsl #3]        // load list 2 element
   cmp x6,x8                    // compar
   bgt 4f
   beq 2f                       // list 1 = list 2
   add x4,x4,1                  // increment index 1
   cmp x4,x1                    // end list ?
   bge 5f
   b 1b                         // else loop

2:

   add x4,x4,1                  // increment index 1
   cmp x4,x1                    // end list ?
   bge 3f                       // yes -> verif size
   add x5,x5,1                  // else increment index 2
   cmp x5,x3                    // end list 2 ?
   bge 4f
   b 1b                         // else loop

3:

   cmp x1,x3                     // compar size
   bge 4f                       // list 2 < list 1
   blt 5f                       // list 1 < list 2
   b 100f

4:

   mov x0,#0                    // list 1 > list 2
   b 100f

5:

   mov x0,#1                    //  list 1 < list 2
   b 100f

98: // error

   mov x0,-2
   b 100f

99: // error

   mov x0,-1

100:

   ldp x2,x3,[sp],16            // restaur  2 registers
   ldp x1,lr,[sp],16            // restaur  2 registers
   ret                          // return to address lr x30

/********************************************************/ /* File Include fonctions */ /********************************************************/ /* for this file see task include a file in language AArch64 assembly */ .include "../includeARM64.inc"

</lang>

ACL2

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

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: <lang Ada> 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; </lang>

Output:

TRUE
TRUE
FALSE
TRUE
TRUE

Aime

<lang aime>ordl(list a, b) {

   integer i, l, o;

   l = min(~a, ~b);
   i = 0;
   while (i < l) {
       if (a[i] != b[i]) {
           o = a[i] < b[i];
           break;
       }

       i += 1;
   }

   i < l ? o : ~a <= ~b;

}

main(void) {

   o_(ordl(list(1, 2), list(1, 2)), "\n");
   o_(ordl(list(1e2, 2), list(1e2, 2, 3)), "\n");
   o_(ordl(list(1, 2, 3), list(1, 2)), "\n");
   o_(ordl(list(.5, 4), list(.5, 2)), "\n");
   o_(ordl(list(1, 4, 2, 3), list(1, 4, 2.1, 3)), "\n");

0;

}</lang>

AppleScript

Translation of: JavaScript

<= is not defined over lists in AppleScript <lang 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</lang>

Output:

<lang AppleScript>{false, true}</lang>

Here's an iterative implementation:

<lang applescript>on listAComesBeforeListB(a, b)

   set aLength to (count a)
   set bLength to (count b)
   set i to 0
   repeat
       set i to i + 1
       if (i > bLength) then
           return false
       else if (i > aLength) then
           return true
       else
           set aVal to item i of a
           set bVal to item i of b
           if (aVal = bVal) then
           else
               return (bVal > aVal)
           end if
       end if
   end repeat

end listAComesBeforeListB

-- Test code: set a to {} repeat (random number 10) times

   set end of a to random number 10

end repeat set b to {} repeat (random number 10) times

   set end of b to random number 10

end repeat

return {a:a, b:b, | a < b |: listAComesBeforeListB(a, b)},</lang>

Output:

Examples: <lang applescript>{a:{3, 5, 6, 5, 2, 1, 4}, b:{5, 8, 9, 2, 0, 1, 9, 0, 4, 10}, | a < b |:true} {a:{10, 9, 5, 8, 8, 4, 3}, b:{5, 10, 8, 9, 10, 8, 7, 8}, | a < b |:false} {a:{0, 10}, b:{0, 10}, | a < b |:false} {a:{0, 10}, b:{0, 10, 5}, | a < b |:true}</lang>

ARM Assembly

Works with: as version Raspberry Pi

<lang ARM Assembly> /* ARM assembly Raspberry PI */ /* program orderlist.s */

/* Constantes */ .equ STDOUT, 1 @ Linux output console .equ EXIT, 1 @ Linux syscall .equ WRITE, 4 @ Linux syscall

/*********************************/ /* Initialized data */ /*********************************/ .data szMessResult1: .asciz "List1 < List2 \n" @ message result szMessResult2: .asciz "List1 => List2 \n" @ message result szCarriageReturn: .asciz "\n"

iTabList1: .int 1,2,3,4,5 .equ NBELEMENTS1, (. - iTabList1) /4 iTabList2: .int 1,2,1,5,2,2 .equ NBELEMENTS2, (. - iTabList2) /4 iTabList3: .int 1,2,3,4,5 .equ NBELEMENTS3, (. - iTabList3) /4 iTabList4: .int 1,2,3,4,5,6 .equ NBELEMENTS4, (. - iTabList4) /4 /*********************************/ /* UnInitialized data */ /*********************************/ .bss /*********************************/ /* code section */ /*********************************/ .text .global main main: @ entry of program

   ldr r0,iAdriTabList1
   mov r1,#NBELEMENTS1
   ldr r2,iAdriTabList2
   mov r3,#NBELEMENTS2
   bl listeOrder
   cmp r0,#0                               @ false ?
   beq 1f                                  @ yes
   ldr r0,iAdrszMessResult1                @ list 1 < list 2
   bl affichageMess                        @ display message
   b 2f

1:

   ldr r0,iAdrszMessResult2
   bl affichageMess                        @ display message

2:

   ldr r0,iAdriTabList1
   mov r1,#NBELEMENTS1
   ldr r2,iAdriTabList3
   mov r3,#NBELEMENTS3
   bl listeOrder
   cmp r0,#0                               @ false ?
   beq 3f                                  @ yes
   ldr r0,iAdrszMessResult1                @ list 1 < list 2
   bl affichageMess                        @ display message
   b 4f

3:

   ldr r0,iAdrszMessResult2
   bl affichageMess                        @ display message

4:

   ldr r0,iAdriTabList1
   mov r1,#NBELEMENTS1
   ldr r2,iAdriTabList4
   mov r3,#NBELEMENTS4
   bl listeOrder
   cmp r0,#0                               @ false ?
   beq 5f                                  @ yes
   ldr r0,iAdrszMessResult1                @ list 1 < list 2
   bl affichageMess                        @ display message
   b 6f

5:

   ldr r0,iAdrszMessResult2
   bl affichageMess                        @ display message

6: 100: @ standard end of the program

   mov r0, #0                              @ return code
   mov r7, #EXIT                           @ request to exit program
   svc #0                                  @ perform the system call

iAdriTabList1: .int iTabList1 iAdriTabList2: .int iTabList2 iAdriTabList3: .int iTabList3 iAdriTabList4: .int iTabList4 iAdrszMessResult1: .int szMessResult1 iAdrszMessResult2: .int szMessResult2 iAdrszCarriageReturn: .int szCarriageReturn /******************************************************************/ /* display text with size calculation */ /******************************************************************/ /* r0 contains the address of list 1 */ /* r1 contains list 1 size */ /* r2 contains the address of list 2 */ /* r3 contains list 2 size */ /* r0 returns 1 if list1 < list2 */ /* r0 returns 0 else */ listeOrder:

   push {r1-r7,lr}                   @ save  registres
   cmp r1,#0                         @ list 1 size = zero ?
   moveq r0,#-1                      @ yes -> error
   beq 100f
   cmp r3,#0                         @ list 2 size = zero ?
   moveq r0,#-2                      @ yes -> error
   beq 100f
   mov r4,#0                         @ index list 1
   mov r5,#0                         @ index list 2

1:

   ldr r6,[r0,r4,lsl #2]             @ load list 1 element
   ldr r7,[r2,r5,lsl #2]             @ load list 2 element
   cmp r6,r7                         @ compar
   movgt r0,#0                       @ list 1 > list 2 ?
   bgt 100f
   beq 2f                            @ list 1 = list 2
   add r4,#1                         @ increment index 1
   cmp r4,r1                         @ end list ?
   movge r0,#1                       @ yes -> ok list 1 < list 2
   bge 100f
   b 1b                              @ else loop

2:

   add r4,#1                         @ increment index 1
   cmp r4,r1                         @ end list ?
   bge 3f                            @ yes -> verif size
   add r5,#1                         @ else increment index 2
   cmp r5,r3                         @ end list 2 ?
   movge r0,#0                       @ yes -> list 2 < list 1
   bge 100f
   b 1b                              @ else loop

3:

  cmp r1,r3                          @ compar size
  movge r0,#0                        @ list 2 < list 1
  movlt r0,#1                        @ list 1 < list 2

100:

   pop {r1-r7,lr}                    @ restaur registers
   bx lr                             @ return

/******************************************************************/ /* display text with size calculation */ /******************************************************************/ /* r0 contains the address of the message */ affichageMess:

   push {r0,r1,r2,r7,lr}                   @ save  registres
   mov r2,#0                               @ counter length

1: @ loop length calculation

   ldrb r1,[r0,r2]                         @ read octet start position + index 
   cmp r1,#0                               @ if 0 its over 
   addne r2,r2,#1                          @ else add 1 in the length 
   bne 1b                                  @ and loop 
                                           @ so here r2 contains the length of the message 
   mov r1,r0                               @ address message in r1 
   mov r0,#STDOUT                          @ code to write to the standard output Linux 
   mov r7, #WRITE                          @ code call system "write" 
   svc #0                                  @ call systeme 
   pop {r0,r1,r2,r7,lr}                    @ restaur registers */ 
   bx lr                                   @ return

</lang>

AutoHotkey

Works with: AutoHotkey_L

The function is overkill as we can just compare the list's ObjMaxIndex() <lang AHK>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() }</lang>

AWK

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)

} </lang>

Output:

list1<list2
list2<list3
list3>=list4

BBC BASIC

'Ordered before' means 'less than' (see talk page). <lang bbcbasic> 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%</lang>

Output:

list1<list2
list2<list3
list3>=list4

Bracmat

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. <lang bracmat>( 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) );</lang>

Output:

TRUE
TRUE
FALSE
FALSE
TRUE
TRUE

C

<lang c>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; }</lang> This funciton returns one of three states, not a boolean. One can define boolean comparisons, such as list_less_or_eq, based on it:<lang c>#define list_less_or_eq(a,b,c,d) (list_cmp(a,b,c,d) != 1)</lang>

C#

<lang csharp>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}));
       }
   }

}</lang>

Output:

False

C++

The built-in comparison operators already do this: <lang cpp>#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;

}</lang>

clojure

<lang clojure> (defn lex? [a b]

 (compare a b))

</lang>

Common Lisp

<lang Lisp>(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)))))</lang>

Alternate version

<lang Lisp>(defun list< (a b)

 (let ((x (find-if-not #'zerop (mapcar #'- a b))))
   (if x (minusp x) (< (length a) (length b)))))</lang>

D

The built-in comparison operators already do this: <lang d>void main() {

   assert([1,2,1,3,2] >= [1,2,0,4,4,0,0,0]);

}</lang>

Delphi

Library: System.SysUtils

Library: System.Generics.Defaults

Translation of: Java

This is not a full translate of Java, just adaptation and aplication of method previus introduced. <lang Delphi> program Order_two_numerical_lists;

{$APPTYPE CONSOLE}

uses

 System.SysUtils,
 System.Generics.Defaults;

type

 TArray = record
   class function LessOrEqual<T>(first, second: TArray<T>): Boolean; static;
 end;

class function TArray.LessOrEqual<T>(first, second: TArray<T>): Boolean; begin

 if Length(first) = 0 then
   exit(true);
 if Length(second) = 0 then
   exit(false);
 var comp := TComparer<T>.Default.Compare(first[0], second[0]);
 if comp = 0 then
   exit(LessOrEqual(copy(first, 1, length(first)), copy(second, 1, length(second))));
 Result := comp < 0;

end;

begin

 writeln(TArray.LessOrEqual<Integer>([1, 2, 3], [2, 3, 4]));
 writeln(TArray.LessOrEqual<Integer>([2, 3, 4], [1, 2, 3]));
 writeln(TArray.LessOrEqual<Integer>([1, 2], [1, 2, 3]));
 writeln(TArray.LessOrEqual<Integer>([1, 2, 3], [1, 2]));
 writeln(TArray.LessOrEqual<Char>(['a', 'c', 'b'], ['a', 'b', 'b']));
 writeln(TArray.LessOrEqual<string>(['this', 'is', 'a', 'test'], ['this', 'is',
   'not', 'a', 'test']));
 readln;

end.</lang>

Output:

TRUE
FALSE
TRUE
FALSE
FALSE
TRUE

Ela

<lang ela>[] <. _ = 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]</lang>

Elixir

The built-in comparison functions already do this (not only for lists of numbers, but for any arbitrary data type). <lang elixir>iex(1)> [1,2,3] < [1,2,3,4] true iex(2)> [1,2,3] < [1,2,4] true</lang>

Erlang

Builtin. Example use from Erlang shell: <lang Erlang> 5> [1,2,3] < [1,2,3,4]. true 6> [1,2,3] < [1,2,4]. true </lang>

F#

By using the Collection.Seq Module the static method Seq.compareWith fits our needs. <lang fsharp>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)</lang>

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

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

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

FreeBASIC

Translation of: BBC BASIC

<lang freebasic>Dim Shared list1(4) As Integer = {1, 2, 1, 5, 2} Dim Shared list2(5) As Integer = {1, 2, 1, 5, 2, 2} Dim Shared list3(4) As Integer = {1, 2, 3, 4, 5} Dim Shared list4(4) As Integer = {1, 2, 3, 4, 5}

Function Orden(listA() As Integer, listB() As Integer) As Boolean

   Dim As Integer i = 0, l1, l2
   l1 = Ubound(listA, 1) 
   l2 = Ubound(listB, 1)
   While listA(i) = listB(i) And i < l1 And i < l2
       i += 1
   Wend
   If listA(i) < listB(i) Then Return True
   If listA(i) > listB(i) Then Return False
   Return l1 < l2

End Function

If Orden(list1(), list2()) Then Print "list1<list2" Else Print "list1>=list2" If Orden(list2(), list3()) Then Print "list2<list3" Else Print "list2>=list3" If Orden(list3(), list4()) Then Print "list3<list4" Else Print "list3>=list4"

Sleep</lang>

Output:

Igual que la entrada de BBC BASIC.

Go

<lang go>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

}</lang>

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

Solution: <lang groovy>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()
   }

}</lang>

Test: <lang groovy>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)</lang>

Haskell

The built-in comparison operators already do this: <lang haskell>Prelude> [1,2,1,3,2] < [1,2,0,4,4,0,0,0] False</lang>

Icon and Unicon

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

<lang Icon>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</lang>

J

J's built-in comparator operates element-wise. To compare general sequences you can either box them and use sort. Or for numeric sequences append minus infinity and sort. However numeric scalars sort ahead of vectors, i.e. are different from length one lists.

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

Below demonstrates non-decreasing order cmp treats length one vector same as scalar

  cmp&.>"{~ (;0;(,0);1;(,1);1 1)

┌─┬─┬─┬─┬─┬─┐ │0│1│1│1│1│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│1│1│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│1│1│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│0│0│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│0│0│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│0│0│0│ └─┴─┴─┴─┴─┴─┘

before&.>"{~ (0;1;;(,0);(,1);1 1) ┌─┬─┬─┬─┬─┬─┐ │0│1│1│1│1│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│1│1│1│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│1│1│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│0│1│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│0│0│1│ ├─┼─┼─┼─┼─┼─┤ │0│0│0│0│0│0│ └─┴─┴─┴─┴─┴─┘</lang>

Java

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. <lang java5>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; } }</lang>

JavaScript

ES6

<= is already defined for numeric lists in JavaScript

<lang 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]

})() </lang>

Output:

<lang JavaScript>[false, true]</lang>

Joy

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

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

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

Julia

Works with: Julia version 0.6

<lang julia>function islexless(a::AbstractArray{<:Real}, b::AbstractArray{<:Real})

   for (x, y) in zip(a, b)
       if x == y continue end
       return x < y
   end
   return length(a) < length(b)

end

using Primes, Combinatorics 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("List not sorted:\n - ", join(tests, "\n - ")) sort!(tests; lt=islexless) println("List sorted:\n - ", join(tests, "\n - "))</lang>

Output:

List not sorted:
 - [1, 2, 3]
 - [2, 3, 5, 7]
 - 0:2:6
 - [-Inf, 0.0, Inf]
 - [3.14159, 2.71828, 1.61803, 0.915966]
 - [2015, 5]
 - [-7.07107, 2500.0]
List sorted:
 - [-Inf, 0.0, Inf]
 - [-7.07107, 2500.0]
 - 0:2:6
 - [1, 2, 3]
 - [2, 3, 5, 7]
 - [3.14159, 2.71828, 1.61803, 0.915966]
 - [2015, 5]

Klingphix

<lang Klingphix>include ..\Utilitys.tlhy

( 1 2 3 ) ( 1 2 3 4 ) less ? ( 1 2 3 4 ) ( 1 2 3 ) less ? ( 1 2 4 ) ( 1 2 3 ) less ? ( 1 2 3 ) ( 1 2 3 ) less ? ( 1 2 3 ) ( 1 2 4 ) less ?

"End " input</lang>

Kotlin

<lang scala>// 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]}")

}</lang>

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

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.

Lasso

This is built into the Lasso comparison operators <lang Lasso>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</lang>

Output:

false
true

Lhogho

Uses standard '=' notation

<lang logo>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</lang>

Output:

<lang logo>true false false false false</lang>

Lua

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:

<lang lua>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</lang>

Here is some demonstration code:

<lang lua>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</lang>

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}

Maple

<lang Maple>orderLists := proc(num1,num2) local len1, len2,i: len1,len2 := numelems(num1),numelems(num2): for i to min(len1,len2) do if num1[i] <> num2[i] then return evalb(num1[i]<num2[i]): end if: end do: return evalb(len1 < len2): end proc:</lang>

Mathematica

<lang Mathematica> 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
  ]]</lang>

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

<lang maxima>"<<"(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</lang>

Mercury

For a particular numerical type, you can get away with

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

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

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

... which you would have to create:

<lang Mercury>:- 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</lang>

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

<lang Mercury>:- 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" }.</lang>

Nim

<lang nim>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])</lang>

Output:

false

OCaml

The built-in comparison operators already do this for lists (although this is not documented): <lang ocaml># [1;2;1;3;2] < [1;2;0;4;4;0;0;0];; - : bool = false</lang>

(Warning: However, the built-in comparison operators do not do this for arrays: <lang ocaml># [|1;2;1;3;2|] < [|1;2;0;4;4;0;0;0|];; - : bool = true</lang> )

But we could write it explicitly this way:

<lang ocaml>let rec ordered_lists = function

 | x1::tl1, x2::tl2 ->
     (match compare x1 x2 with
     | 0 -> ordered_lists (tl1, tl2)
     | 1 -> false
     | _ -> true)
 | [], _ -> true
 | _ -> false</lang>

Here is a small script to test this function:

<lang ocaml>(* 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))</lang>

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:

<lang ocaml>val ordered_lists : 'a list * 'a list -> bool</lang>

Oforth

In Oforth, list comparison is already defined.

Output:

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

Ol

This sample very similar to Scheme, but implements proper tail recursion. So can test unlimited length lists. <lang scheme> (define (lexorder a b)

  (cond
     ((null? b) #false)
     ((null? a) #true)
     ((< (car a) (car b)) #true)
     ((> (car a) (car b)) #false)
     (else
        (lexorder (cdr a) (cdr b)))))

(print (lexorder '(1 2 3) '(1 2 3 4))) ; => true (print (lexorder '(1 2 4) '(1 2 3))) ; => false (print (lexorder '(1 2 3) '(1 2))) ; => false (print (lexorder '(1 2 3) '(1 2 3))) ; => false (print (lexorder '(1 2 3) '(1 2 8))) ; => true </lang>

PARI/GP

Perl

<lang Perl>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";

}</lang>

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

Phix

Handled natively, eg ("?" is the shorthand print operator) <lang Phix>?{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</lang> 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.

Phixmonti

Translation of: Phix

<lang Phixmonti>include Utilitys.pmt

def ? print nl enddef

( 1 2 3 ) ( 1 2 3 4 ) < ? ( 1 2 3 4 ) ( 1 2 3 ) < ? ( 1 2 4 ) ( 1 2 3 ) < ? ( 1 2 3 ) ( 1 2 3 ) < ? ( 1 2 3 ) ( 1 2 4 ) < ?</lang>

PicoLisp

The built-in comparison functions already do this (not only for lists of numbers, but for any arbitrary data type). <lang PicoLisp>: (> (1 2 0 4 4 0 0 0) (1 2 1 3 2)) -> NIL</lang>

Pike

<lang Pike>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];

}</lang> 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: <lang Pike>(string)a < (string)b;</lang>

PL/I

<lang PL/I>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;</lang> Results:

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

PowerShell

<lang PowerShell> 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))" </lang> Output:

False

Non-Recursive Version

<lang PowerShell> 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

} </lang> <lang PowerShell> 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 </lang>

Output:

False
True
False
True
True

PureBasic

<lang purebasic>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

 </lang>

Output:

False
False
False
True
True

Python

The built-in comparison operators already do this: <lang python>>>> [1,2,1,3,2] < [1,2,0,4,4,0,0,0] False</lang>

Racket

<lang Racket>#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 </lang>

Raku

(formerly Perl 6) There is already a built-in comparison operator. <lang perl6>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;

}</lang>

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

Rascal

The built-in comparison operator already does this: <lang rascal>rascal>[2,1,3] < [5,2,1,3] bool: true</lang>

REXX

This REXX example uses the same lists as BBC BASIC.

This example will also work with non-numeric strings. <lang rexx>/*REXX program determines if a list < previous list, and returns true or 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 a list to previous list*/
        do j=2  while  @.j\==;      p= j - 1  /*P:  points to previous value in list.*/
        if FNorder(@.p, @.j)=='true'  then is= " < "       /*use a more familiar glyph.*/
                                      else is= " ≥ "       /* "  "   "      "      "   */
        say
        say right('['@.p"]", 40)  is  '['@.j"]"
        end   /*i*/

exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ FNorder: procedure; parse arg x,y

        wx= words(x);     wy= words(y)
                                        do k=1  for min(wx, wy)
                                           a= word(x, k)         /*get a value from X. */
                                           b= word(y, k)         /* "  "   "     "  Y. */
                                        if ab  then  return 'false'
                                        end   /*k*/
        if wx<wy  then return 'true'                  /*handle case of equal (so far). */
                       return 'false'                 /*   "     "   "   "     "   "   */</lang>

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
<lang ring> 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)
</lang> Output:
list1<list2 list2>list3 list3=list4
Ruby
The built-in <=> operator already does this: <lang ruby>>> ([1,2,1,3,2] <=> [1,2,0,4,4,0,0,0]) < 0 => false</lang>
Rust
Vec<T> implements Ord when T does, so we can just compare them with <. (Same with arrays and slices). <lang Rust>vec![1, 2, 1, 3, 2] < vec![1, 2, 0, 4, 4, 0, 0, 0]</lang>
Scala
<lang Scala>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)</lang><lang Scala>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)
}</lang><lang Scala>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)</lang><lang Scala>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)
}</lang>
Scheme
<lang scheme>(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)))))</lang>
Seed7
The operator corresponding to the ordering described in this example is less than.
<lang seed7>$ 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;</lang>

Output:
TRUE FALSE FALSE FALSE TRUE TRUE FALSE FALSE
Sidef
Built-in, via the comparison operator (`<=>`): <lang ruby>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}"
}</lang>

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
<lang sml>- List.collate Int.compare ([1,2,1,3,2], [1,2,0,4,4,0,0,0]) = LESS; val it = false : bool</lang>
Swift
<lang swift>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"</lang>

Output:
false
Tcl
<lang tcl>proc numlist< {A B} {
foreach a $A b $B { if {$a<$b} { return 1 } elseif {$a>$b} { return 0 } } return 0
}</lang>
TUSCRIPT
<lang tuscript> $$ MODE TUSCRIPT MODE DATA $$ 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 </lang>

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
VBA
<lang vb>Private Function order(list1 As Variant, list2 As Variant) As Boolean
i = 1 Do While list1(i) <= list2(i) i = i + 1 If i > UBound(list1) Then order = True Exit Function End If If i > UBound(list2) Then order = False Exit Function End If Loop order = False
End Function Public Sub main()
Debug.Print order([{1, 2, 3, 4}], [{1,2,0,1,2}]) Debug.Print order([{1, 2, 3, 4}], [{1,2,3}]) Debug.Print order([{1, 2, 3}], [{1,2,3,4}])

End Sub</lang>

Output:
Onwaar Onwaar Waar
VBScript
<lang vb> 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)) </lang>

Output:
PASS FAIL FAIL PASS PASS PASS FAIL FAIL PASS FAIL
Wart
We'll simply overload < for lists. <lang python>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)</lang>

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
Wren
<lang ecmascript>var orderLists = Fn.new { |l1, l2|
var len = (l1.count <= l2.count) ? l1.count : l2.count for (i in 0...len) { if (l1[i] < l2[i]) return true if (l1[i] > l2[i]) return false } return (l1.count < l2.count)
}
var lists = [
[1, 2, 3, 4, 5], [1, 2, 1, 5, 2, 2], [1, 2, 1, 5, 2], [1, 2, 1, 5, 2], [1, 2, 1, 3, 2], [1, 2, 0, 4, 4, 0, 0, 0], [1, 2, 0, 4, 4, 1, 0, 0], [1, 2, 0, 4, 4, 1, 0, 1]
]
for (i in 0...lists.count) System.print("list[%(i)] : %(lists[i])") System.print() for (i in 0...lists.count-1) {
var res = orderLists.call(lists[i], lists[i+1]) System.print("list[%(i)] < list[%(i+1)] -> %(res)")
}</lang>

Output:
list[0] : [1, 2, 3, 4, 5] list[1] : [1, 2, 1, 5, 2, 2] list[2] : [1, 2, 1, 5, 2] list[3] : [1, 2, 1, 5, 2] list[4] : [1, 2, 1, 3, 2] list[5] : [1, 2, 0, 4, 4, 0, 0, 0] list[6] : [1, 2, 0, 4, 4, 1, 0, 0] list[7] : [1, 2, 0, 4, 4, 1, 0, 1] list[0] < list[1] -> false list[1] < list[2] -> false list[2] < list[3] -> false list[3] < list[4] -> false list[4] < list[5] -> false list[5] < list[6] -> true list[6] < list[7] -> true
zkl
<lang zkl>fcn listLT(a,b){
a.walker().zip(b).filter1(fcn([(a,b)]){ a<b }) : // lazy if(_) return(True);; a.len()<b.len()
}</lang>

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