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Create a function that returns the maximum value in a provided set of values, where the number of values may not be known until runtime.

ACL2

<lang Lisp>(defun maximum (xs)

  (if (endp (rest xs))
      (first xs)
      (max (first xs)
           (maximum (rest xs)))))</lang>

ActionScript

<lang ActionScript>function max(... args):Number { var curMax:Number = -Infinity; for(var i:uint = 0; i < args.length; i++) curMax = Math.max(curMax, args[i]); return curMax; }</lang>

Ada

The keys for this task are initializing the compared value to the 'First value of the element type, and use of an unconstrained array type. <lang ada>with Ada.Text_Io;

procedure Max_Test is

  -- substitute any array type with a scalar element
  type Flt_Array is array (Natural range <>) of Float;
  
  -- Create an exception for the case of an empty array
  Empty_Array : Exception;
  
  function Max(Item : Flt_Array) return Float is
     Max_Element : Float := Float'First;
  begin
     if Item'Length = 0 then 
        raise Empty_Array;
     end if;
 
     for I in Item'range loop
        if Item(I) > Max_Element then
           Max_Element := Item(I);
        end if;
     end loop;
     return Max_Element;
  end Max;
   
  Buf : Flt_Array := (-275.0, -111.19, 0.0, -1234568.0, 3.14159, -3.14159);

begin

  Ada.Text_IO.Put_Line(Float'Image(Max(Buf)));

end Max_Test;</lang> A generic function Max to deal with any floating-point type. <lang ada>generic

  type Item is digits <>;
  type Items_Array is array (Positive range <>) of Item;

function Generic_Max (List : Items_Array) return Item;</lang> Implementation of: <lang ada>function Generic_Max (List : Items_Array) return Item is

  Result : Item := List (List'First);

begin

  for Index in List'First + 1..List'Last loop
     Result := Item'Max (Result, List (Index));
  end loop;
  return Result;

end Generic_Max;</lang> When the argument array is empty, Constraint_Error exception is propagated, because array indexing is checked in Ada. Note also use of the floating-type attribute Max.

ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used

Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny

<lang algol68># substitute any array type with a scalar element # MODE FLT = REAL;

create an exception for the case of an empty array #

PROC raise empty array = VOID:(

 GO TO except empty array

);

PROC max = ([]FLT item)FLT: BEGIN

  IF LWB item > UPB item THEN
     raise empty array; SKIP
  ELSE
    FLT max element := item[LWB item];

    FOR i FROM LWB item + 1 TO UPB item DO
      IF item[i] > max element THEN
        max element := item[i]
      FI
    OD;
    max element
  FI

END # max #;

test:(

 []FLT buf = (-275.0, -111.19, 0.0, -1234568.0, pi, -pi);
 print((max(buf),new line)) EXIT
 except empty array:
   SKIP

)</lang> Output:

+3.14159265358979e  +0

APL

<lang apl>LIST←2 4 6 3 8 ⌈/LIST</lang> Output: <lang apl>8</lang>

AppleScript

<lang AppleScript>on max(aList) set _curMax to first item of aList repeat with i in (rest of aList) if i > _curMax then set _curMax to contents of i end repeat return _curMax end max</lang>

AWK

<lang awk>$ awk 'func max(a){for(i in a)if(a[i]>r)r=a[i];return r}BEGIN{a[0]=42;a[1]=33;a[2]=21;print max(a)}' 42</lang>

BASIC

Works with: QBasic

<lang qbasic>DECLARE SUB addVal (value AS INTEGER) DECLARE FUNCTION findMax% ()

REDIM SHARED vals(0) AS INTEGER DIM SHARED valCount AS INTEGER DIM x AS INTEGER, y AS INTEGER

valCount = -1

begin test run RANDOMIZE TIMER FOR x = 1 TO 10

   y = INT(RND * 100)
   addVal y
   PRINT y; " ";

NEXT PRINT ": "; findMax end test run

SUB addVal (value AS INTEGER)

   DIM tmp AS INTEGER
   IF valCount > -1 THEN
       'this is needed for BASICs that don't support REDIM PRESERVE
       REDIM v2(valCount) AS INTEGER
       FOR tmp = 0 TO valCount
           v2(tmp) = vals(tmp)
       NEXT
   END IF
   valCount = valCount + 1
   REDIM vals(valCount)
   IF valCount > 0 THEN
       'also needed for BASICs that don't support REDIM PRESERVE
       FOR tmp = 0 TO valCount - 1
           vals(tmp) = v2(tmp)
       NEXT
   END IF
   vals(valCount) = value

END SUB

FUNCTION findMax%

   DIM tmp1 AS INTEGER, tmp2 AS INTEGER
   FOR tmp1 = 0 TO valCount
       IF vals(tmp1) > tmp2 THEN tmp2 = vals(tmp1)
   NEXT
   findMax = tmp2

END FUNCTION</lang>

Sample output:

8162   5139   7004   7393   5151   4476   577   4419   3333   4649  :  8162

Batch File

<lang dos>::max.cmd @echo off setlocal enabledelayedexpansion set a=.%~1 if "%a%" equ "." set /p a="Input stream: " call :max res %a% echo %res% endlocal goto :eof

max

set %1=%2

loop

shift /2 if "%2" equ "" goto :eof if %2 gtr !%1! set res=%2 goto loop</lang>

Invocation from command line or from internal prompt

<lang dos>>max "123 456 3 234243 12" 234243

>max Input stream: 5 4 3 2 67 1 67</lang>

BBC BASIC

<lang bbcbasic> ListOfValues$ = "13, 0, -6, 2, 37, -10, 12"

     PRINT "Maximum value = " ; FNmax(ListOfValues$)
     END
     
     DEF FNmax(list$)
     LOCAL index%, number, max
     REPEAT
       number = VAL(MID$(list$, index%+1))
       IF number > max THEN max = number
       index% = INSTR(list$, ",", index%+1)
     UNTIL index% = 0
     = max</lang>

Bracmat

When comparing two rational numbers, Bracmat compares numerically. In all other cases Bracmat compares lexically. <lang> ( biggest

 =   max
   .   !arg:
     |   !arg:%?max ?arg
       & !arg:? (%@:>!max:?max) (?&~)
     | !max
 )

& out$("1:" biggest$(5 100000 -5 aap 3446 NOOT mies 0)) & out$("2:" biggest$) & out

 $ ( "3:"
       biggest
     $ (5 100000 -5 43756243978569758/13 3365864921428443 87512487957139516/27 3446)
   )</lang>

Output:

1: mies
2:
3: 3365864921428443

Burlesque

The following macro can be used with any number and type of arguments, provided that the arguments are simple, i.e. must not contain subexpressions where commas appear (this is because of the way the arguments are counted; the macro can be modified so that it is up to the caller to count the number of arguments passed).

Works with: GCC

<lang c>#include <stdarg.h>

define MAX(A,...) ({ inline __typeof__ (A) _max_(__typeof__ (A) a, ...) {\

 va_list l; int i,c; const char *s = #__VA_ARGS__; __typeof__ (A) max = a;\
 __typeof__ (A) t;\
 for(c=1;*s!=0;s++) if (*s==',') c++;\
 va_start(l, a);\
 for(i=0;i<=c;i++) {\
 if ((t=va_arg(l,__typeof__ (A))) > max) max = t;\
 }\
 va_end(l); return max;\

}\ _max_((A),__VA_ARGS__);\ })</lang>

C++

This will work for any type with a < operator defined. Uses the standard library function max_element(). <lang cpp>#include <algorithm>

include <cassert>

template<typename Ty> Ty max(unsigned int count, Ty values[]) {

    assert(count > 0);
    return *std::max_element(values, values + count);

}</lang>

C#

C# already have a "Maximum Value" function.

<lang csharp>using System.Linq;

values.Max();</lang>

Clojure

The Clojure.core function max returns the max of its arguments. <lang clojure>(max 1 2 3 4) ; evaluates to 4

If the values are already in a collection, use apply

(apply max [1 2 3 4]) ; evaluates to 4</lang>

CMake

Only for lists of integers.

<lang cmake># max(var [value1 value2...]) sets var to the maximum of a list of

integers. If list is empty, sets var to NO.

function(max var)

 set(first YES)
 set(choice NO)
 foreach(item ${ARGN})
   if(first)
     set(choice ${item})
     set(first NO)
   elseif(choice LESS ${item})
     set(choice ${item})
   endif()
 endforeach(item)
 set(${var} ${choice} PARENT_SCOPE)

endfunction(max)

set(list 33 11 44 22 66 55) max(maximum ${list}) message(STATUS "maximum of ${list} => ${maximum}")</lang>

-- maximum of 33;11;44;22;66;55 => 66

CoffeeScript

using Math library

max1 = (list) ->

Math.max.apply null, list

using no libraries

max2 = (list) ->

maxVal = list[0]
for value in list
 maxVal = value if value > maxVal
maxVal

Test it

a = [0,1,2,5,4]; alert(max1(a)+". The answer is "+max2(a)); </lang>

Common Lisp

The built-in Common Lisp function max takes the max of all its arguments. <lang lisp>(max 1 2 3 4) (reduce #'max values) ; find max of a list (loop for x in values

     maximize x) ; alternative way to find max of a list</lang>

D

<lang d>import std.stdio, std.algorithm;

void main() {

   auto items = [9, 4, 3, 8, 5];
   auto m = reduce!max(items);
   writeln(m);

}</lang>

Dart

<lang Dart>/*This is a function which returns the greatest element in a list of numbers */ num findGreatestElement(List<num> list){

 num greatestElement = list[0];
 for (num element in list){
   if (element>greatestElement) {
     greatestElement = element;
   }
 }  
 return greatestElement;

} </lang>

Delphi

<lang Delphi>Math.MaxIntValue(); // Array of Integer Math.MaxValue(); // Array of floating point (Single, Double or Extended) </lang>

E

This function works for any value which responds to max/1:

<lang e>pragma.enable("accumulator") # non-finalized syntax feature

def max([first] + rest) {

   return accum first for x in rest { _.max(x) }

}</lang>

<lang e>? max([1, 2, 3])

value: 3</lang>

To require only the comparison protocol, one needs to write out the algorithm a little more explicitly:

<lang e>def max([var bestSoFar] + rest) {

   for x ? (x > bestSoFar) in rest {
       bestSoFar := x
   }
   return bestSoFar

}</lang>

<lang e>? max([1, 3, 2])

value: 3

? max([[1].asSet(), [2].asSet(), [1, 2].asSet()])

value: [1, 2].asSet()</lang>

Efene

<lang efene>list_max = fn ([Head:Rest]) {

 list_max(Rest, Head)

}

list_max = fn ([], Res) {

Res

} fn ([Head:Rest], Max) when Head > Max {

 list_max(Rest, Head)

} fn ([_Head:Rest], Max) {

 list_max(Rest, Max)

}

list_max1 = fn ([H:T]) {

 lists.foldl(fn erlang.max:2, H, T)

}

@public run = fn () {

   io.format("~p~n", [list_max([9, 4, 3, 8, 5])])
   io.format("~p~n", [list_max1([9, 4, 3, 8, 5])])

} </lang>

Ela

<lang ela>open list

findBy p (x::xs) = foldl (\x y | p x y -> x | else -> y) x xs maximum = findBy (>)

maximum [1..10]</lang>

Emacs Lisp

<lang lisp>(defun max (first-arg &rest more-args)

 (if more-args
     (let ((max-rest (apply 'max more-args)))

(if (> first-arg max-rest) first-arg max-rest))

   first-arg))</lang>

Example use: <lang lisp>(max 2 7 5) 7</lang>

Erlang

Builtin. Using it from the Erlang shell: <lang erlang>>lists:max([9,4,3,8,5]). 9</lang>

Euler Math Toolbox

<lang> >v=random(1,100); >max(v)

0.997492478596

</lang>

Euphoria

Applying a function to each element of an array

<lang Euphoria>function aeval( sequence sArr, integer id )

   for i = 1 to length( sArr ) do
       sArr[ i ] = call_func( id, { sArr[ i ] } )
   end for
   return sArr

end function

object biggun function biggest( object elem )

   if compare(elem, biggun) > 0 then
       biggun = elem
   end if
   return elem

end function

biggun = 0 object a a = aeval( {1,1234,62,234,12,34,6}, routine_id("biggest") ) printf( 1, "%d\n", biggun )

sequence s s = {"antelope", "dog", "cat", "cow", "wolf", "wolverine", "aardvark"} biggun = "ant" a = aeval( s, routine_id("biggest") ) printf( 1, "%s\n", {biggun} )</lang> Output:

1234
wolverine

More trivial example

<lang euphoria>function get_biggest(sequence s)

   object biggun
   biggun = s[1]
   for i = 2 to length(s) do
       if compare(s[i], biggun) > 0 then
           biggun = s[i]
       end if
   end for
   return biggun

end function

constant numbers = {1,1234,62,234,12,34,6} printf(1,"%d\n",get_biggest(numbers))

constant animals = {"ant", "antelope", "dog", "cat", "cow", "wolf", "wolverine", "aardvark"} printf(1,"%s\n",{get_biggest(animals)})</lang>

Output:

1234
wolverine

F#

F# has a built in function for getting the max of a list:

To use as a function <lang fsharp>let ListMax n = n |> List.max</lang>

Factor

The following word is in factor's standard library. <lang factor>: supremum ( seq -- elt ) [ ] [ max ] map-reduce ;</lang>

Fancy

<lang fancy>[1,-2,2,4,6,-4,-1,5] max println # => 6</lang>

Fantom

Has a built-in method to get maximum from a list.

<lang fantom> class Greatest {

 public static Void main () 
 {
   Int[] values := [1,2,3,4,5,6,7,8,9]
   Int greatest := values.max
   echo (greatest)
 }

} </lang>

Forth

<lang forth>: array-max ( addr len -- max )

 dup 0= if nip exit then
 over @  rot cell+  rot 1-
 cells bounds ?do  i @ max  cell +loop ;

stack-max ( n ... m count -- max ) 1 ?do max loop ;</lang>

Fortran

Works with: Fortran version 2003

The intrinsic function maxval returns the maximum value of the elements in an integer or real array:

<lang fortran>program test_maxval

integer,dimension(5),parameter :: x = [10,100,7,1,2] real,dimension(5),parameter :: y = [5.0,60.0,1.0,678.0,0.0]

write(*,'(I5)') maxval(x) write(*,'(F5.1)') maxval(y)

end program test_maxval</lang>

Output:

100
678.0

The intrinsic function max accepts any number of arguments. The type of these arguments can be integer, real, character, string of characters or arrays of these. <lang fortran>program test_max

 implicit none

 write (*, '(i0)') &
   & max (1, 2, 3)
 write (*, '(f3.1)') &
   & max (1.0, 2.0, 3.0)
 write (*, '(a)') &
   & max ('a', 'b', 'c')
 write (*, '(a)') &
   & max ('abc', 'bca', 'cab')
 write (*, '(i0, 2 (1x, i0))') &
   & max ([1, 8, 6], [7, 5, 3], [4, 2, 9])
 write (*, '(f3.1, 2 (1x, f3.1))') &
   & max ([1.0, 8.0, 6.0], [7.0, 5.0, 3.0], [4.0, 2.0, 9.0])
 write (*, '(a, 2 (1x, a))') &
   & max (['a', 'h', 'f'], ['g', 'e', 'c'], ['d', 'b', 'i'])
 write (*, '(a, 2 (1x, a))') &
   & max (['abc', 'hig', 'fde'], ['ghi', 'efd', 'cab'], ['def', 'bca', 'igh'])

end program test_max</lang> Output:

3
3.0
c
cab
7 8 9
7.0 8.0 9.0
g h i
ghi hig igh

Frink

<lang frink> println[max1,2,3,5,10,20] </lang>

GAP

<lang gap># Built-in

L := List([1 .. 100], n -> Random(1, 10));

MaximumList(L);

10</lang>

Go

List

The task title says list. This solution uses a Go slice as a list. <lang go>package main

import (

   "fmt"
   "math/rand"
   "time"

)

// function, per task description func largest(a []int) (lg int, ok bool) {

   if len(a) == 0 {
       return
   }
   lg = a[0]
   for _, e := range a[1:] {
       if e > lg {
           lg = e
       }
   }
   return lg, true

}

func main() {

   // random size slice
   rand.Seed(time.Now().UnixNano())
   a := make([]int, rand.Intn(11))
   for i := range a {
       a[i] = rand.Intn(101) - 100 // fill with random numbers
   }

   fmt.Println(a)
   lg, ok := largest(a)
   if ok {
       fmt.Println(lg)
   } else {
       fmt.Println("empty list.  no maximum.")
   }

}</lang>

Set

The task description says set. This solution uses a Go map as a set. <lang go>package main

import (

   "fmt"
   "math"
   "math/rand"
   "time"

)

// Function, per task description. Interesting with the float64 type because // of the NaN value. NaNs do not compare to other values, so the result of // a "largest" function on a set containing a NaN might be open to // interpretation. The solution provided here is to return the largest // of the non-NaNs, and also return a bool indicating the presense of a NaN. func largest(s map[float64]bool) (lg float64, ok, nan bool) {

   if len(s) == 0 {
       return
   }
   for e := range s {
       switch {
       case math.IsNaN(e):
           nan = true
       case !ok || e > lg:
           lg = e
           ok = true
       }
   }
   return

}

func main() {

   rand.Seed(time.Now().UnixNano())
   // taking "set" literally from task description
   s := map[float64]bool{}
   // pick number of elements to add to set
   n := rand.Intn(11)
   // add random numbers, also throw in an occasional NaN or Inf.
   for i := 0; i < n; i++ {
       switch rand.Intn(10) {
       case 0:
           s[math.NaN()] = true
       case 1:
           s[math.Inf(1)] = true
       default:
           s[rand.ExpFloat64()] = true
       }
   }

   fmt.Print("s:")
   for e := range s {
       fmt.Print(" ", e)
   }
   fmt.Println()
   switch lg, ok, nan := largest(s); {
   case ok && !nan:
       fmt.Println("largest:", lg)
   case ok:
       fmt.Println("largest:", lg, "(NaN present in data)")
   case nan:
       fmt.Println("no largest, all data NaN")
   default:
       fmt.Println("no largest, empty set")
   }

}</lang>

Golfscript

<lang golfscript>{$-1=}:max; [1 4 8 42 6 3]max # Example usage</lang>

Groovy

<lang groovy>println ([2,4,0,3,1,2,-12].max())</lang>

Output:

Haskell

The built-in Haskell function maximum already does this. <lang haskell>my_max = maximum</lang> It can alternately be defined as a "fold" on the built-in two-argument max function. <lang haskell>my_max = foldl1 max</lang>

HicEst

  max_value = MAX( -123,  234.56, 345.678, -456E3, -455) ! built-in function MAX(...)

! or for an array:

  max_value = MAX( array_of_values )

! or to find a maximum value in a file named filename:

  CHARACTER List, filename='Greatest element of a list.hic' ! filename contains this script
  REAL values(1) ! unknown number of values, allocate more below

  OPEN(FIle=filename, BINary, LENgth=len)
  ALLOCATE(values, len/2) ! number of values <= half byte count of file
  ! read all values, returns item count in values_found:
  READ(FIle=filename, ItemS=values_found, CLoSe=1) values ! no Format needed for plain text numbers

  max_value = MAX(values)

  ! write values found in filename and result to spreadsheet type dialog window:
  DLG(Text=values, Text=max_value, TItle=values_found)

  WRITE(ClipBoard, Name) max_value, values_found, values ! pasted to line below
  ! max_value=345.678; values_found=30; values(1)=-123; values(2)=234.56; values(3)=345.678; values(4)=-456E3; values(5)=-455; values(6)=1; values(7)=2; values(8)=1; values(9)=0; values(10)=0; ...truncated
END

</lang>

Icon and Unicon

<lang icon>procedure main()

  local l
  l := [7,8,6,9,4,5,2,3,1]
  write(max(l))

end

procedure max(l)

  local max
  max := l[1]
  every max <:= !l
  return max

end</lang>

J

Solution:<lang j> >./</lang> Example:<lang J> >./ 1 2 3 2 1 3

  >./  NB.  Maximum value of an empty list = identity element (or neutral) of max = -∞

__</lang>

Java

The first function works with arrays of floats. Replace with arrays of double, int, or other primitive data type. <lang java>public static float max(float[] values) throws NoSuchElementException {

   if (values.length == 0)
       throw new NoSuchElementException();
   float themax = values[0];
   for (int idx = 1; idx < values.length; ++idx) {
       if (values[idx] > themax)
           themax = values[idx];
   }
   return themax;

}</lang>

Optionally, if it is OK to rearrange the contents of the original array: <lang java>public static float max(float[] values) throws NoSuchElementException {

   if (values.length == 0)
       throw new NoSuchElementException();
   Arrays.sort(values);//sorts the values in ascending order
   return values[values.length-1];

}</lang>

The following functions work with Lists or arrays of reference types, respectively. Note that the type is required to implement Comparable, to ensure we can compare them. For Lists, there is a utility method Collections.max() that already does this. For arrays, we can just use the Arrays.asList() wrapper to wrap it into a list and then use the function for lists. <lang java>import java.util.List; import java.util.Collections; import java.util.Arrays;

public static <T extends Comparable<? super T>> T max(List<T> values) {

   return Collections.max(values);

}

public static <T extends Comparable<? super T>> T max(T[] values) {

   return Collections.max(Arrays.asList(values));

}</lang>

JavaScript

Using the built-in Math.max method

<lang javascript>function max(arr) {

return Math.max.apply(null, arr);

}

// Test it a = [0,1,2,5,4]; alert(max(a));</lang>

Julia

<lang julia>julia> max([1,3,3,7]) 7

julia> max([pi,e+2/5,cos(6)/5,sqrt(91/10)]) 3.141592653589793

julia> max([1,6,Inf]) Inf

julia> max(Float64[]) -Inf</lang>

K

Liberty BASIC

<lang lb>aList$= "1 15 -5 6 39 1.5 14"

maxVal = val(word$(aList$, 1)) token$ = "?" while token$ <> ""

   index = index + 1
   token$ = word$(aList$, index)
   aVal = val(token$)
   if aVal > maxVal then maxVal = aVal

wend

print "maxVal = ";maxVal</lang>

Logo

Works with: UCB Logo

If the template is, like SUM, the name of a procedure that is capable of accepting arbitrarily many inputs, it is more efficient to use APPLY instead of REDUCE. The latter is good for associative procedures that have been written to accept exactly two inputs: <lang logo>to max :a :b output ifelse :a > :b [:a] [:b] end

print reduce "max [...]</lang>

Alternatively, REDUCE can be used to write MAX as a procedure that accepts any number of inputs, as SUM does: <lang logo>to max [:inputs] 2 if emptyp :inputs ~

  [(throw "error [not enough inputs to max])]

output reduce [ifelse ?1 > ?2 [?1] [?2]] :inputs end</lang>

Logtalk

<lang logtalk> max([X| Xs], Max) :-

   max(Xs, X, Max).

max([], Max, Max). max([X| Xs], Aux, Max) :-

   (   X @> Aux ->
       max(Xs, X, Max)
   ;   max(Xs, Aux, Max)
   ).</lang>

Lua

<lang lua>-- Table to store values local values = {} -- Read in the first number from stdin local new_val = io.read"*n" -- Append all numbers passed in -- until there are no more numbers (io.read'*n' = nil) while new_val do

 values[#values+1] = new_val
 new_val = io.read"*n"

end

-- Print the max print(math.max(unpack(values))) </lang>

Maple

This is a built-in, polymorphic procedure in Maple. <lang Maple>> max( { 1, 2, Pi, exp(1) } ); # set

Pi

> max( [ 1, 2, Pi, exp(1) ] ); # list

Pi

> max( 1, 2, Pi, exp(1) ); # sequence

Pi

> max( Array( [ 1, 2, Pi, exp(1) ] ) ); # Array

                                  Pi</lang>

For numeric data in (multi-dimensional) rtables, a particularly flexible and powerful method for finding the maximum (and many other things) is the use of "rtable_scanblock". The maximum of an Array is a built-in rtable_scanblock operation and can be found as follows. <lang Maple>> A := Array([1,2,4/5,3,11]): rtable_scanblock( A, [rtable_dims(A)], Maximum );

                                  11</lang>

Mathematica

Input: <lang Mathematica>Max[1, 3, 3, 7] Max[Pi,E+2/5,17 Cos[6]/5,Sqrt[91/10]] Max[1,6,Infinity] Max[]</lang> Output <lang Mathematica> 7

17 Cos[6]/5
Infinity

-Infinity</lang> Note that Max returns minus infinity if supplied with no arguments; as it should: <lang Mathematica>Max[Max[],Max[a,b,c]] Max[Max[a],Max[b,c]] Max[Max[a,b],Max[c]] Max[Max[a,b,c],Max[]]</lang> should all give the same results, therefore max[] should give -Infinity. If it WOULD give 0 strange this can happen: <lang Mathematica>Max[Max[], Max[-4, -3]]</lang> WOULD give 0 instead of -3

MATLAB

<lang Matlab>function [maxValue] = findmax(setOfValues)

  maxValue = max(setOfValues);</lang>

Maxima

<lang maxima>: makelist(random(1000), 50)$

/* Three solutions */ lreduce(max, u);

apply(max, u);

lmax(u);</lang>

MAXScript

MAXScript has a built-in function called amax(), which will return the maximum of an array or the values supplied to it. The following custom function will return the maximum of the array supplied to it, or 'undefined' if an empty array is supplied. <lang MAXScript>fn MaxValue AnArray = ( if AnArray.count != 0 then ( local maxVal = 0 for i in AnArray do if i > maxVal then maxVal = i maxVal ) else undefined )</lang>

Metafont

The max macro (in the base set of macro for Metafont) accepts any number of arguments, and accepts both numerics (numbers), pairs (bidimensional vectors), and strings (not mixed).

<lang metafont>show max(4,5,20,1); show max((12,3), (10,10), (25,5)); show max("hello", "world", "Hello World");</lang>

МК-61/52

or

Modula-3

Modula-3 provides a builtin MAX function, but it only works on two elements (or enumerations) but not arrays or sets.

We provide a generic Maximum implementation: <lang modula3>GENERIC INTERFACE Maximum(Elem);

EXCEPTION Empty;

PROCEDURE Max(READONLY a: ARRAY OF Elem.T): Elem.T RAISES {Empty};

END Maximum.</lang>

<lang modula3>GENERIC MODULE Maximum(Elem);

PROCEDURE Max(READONLY arr: ARRAY OF Elem.T): Elem.T RAISES {Empty} =

 VAR max := FIRST(Elem.T);
 BEGIN
   IF NUMBER(arr) = 0 THEN
     RAISE Empty;
   END;
   FOR i := FIRST(arr) TO LAST(arr) DO
     IF arr[i] > max THEN
       max := arr[i];
     END;
   END;
   RETURN max;
 END Max;

BEGIN END Maximum.</lang>

Elem can be instantiated to any type (any type that can be compared with the '>' function). For convenience Modula-3 provides interfaces/modules for the built in types, like Integer, Real, LongReal, etc, which contain type definitions as well as properties specific to the type.

To make a generic interface/module for a specific type, you must instantiate it: <lang modula3>INTERFACE RealMax = Maximum(Real) END RealMax.</lang> <lang modula3>MODULE RealMax = Maximum(Real) END RealMax.</lang>

Now we can import RealMax into our source and use the Max function: <lang modula3>MODULE Main;

IMPORT RealMax, IO, Fmt;

VAR realarr := ARRAY [1..5] OF REAL {1.1, 1.0, 0.0, 2.4, 3.3};

BEGIN

 IO.Put(Fmt.Real(RealMax.Max(realarr)) & "\n");

END Main.</lang>

MUMPS

<lang MUMPS> MV(A,U)

;A is a list of values separated by the string U
NEW MAX,T,I
FOR I=1:1 SET T=$PIECE(A,U,I) QUIT:T=""  S MAX=$SELECT(($DATA(MAX)=0):T,(MAX<T):T,(MAX>=T):MAX)
QUIT MAX

</lang> Usage:

USER>SET V=","
 
USER>SET B="-1,-1000,1000,2.3E5,8A,""A"",F"
 
USER>W $$MV^ROSETTA(B,V)
2.3E5

NetRexx

<lang NetRexx>/* NetRexx */

options replace format comments java crossref savelog symbols binary

rn = Random() maxElmts = 100 dlist = double[maxElmts] rlist = Rexx[maxElmts] loop r_ = 0 to maxElmts - 1

 nr = rn.nextGaussian * 100.0
 dlist[r_] = nr
 rlist[r_] = Rexx(nr)
 end r_

say 'Max double:' Rexx(getMax(dlist)).format(4, 9) say 'Max Rexx:' getMax(rlist).format(4, 9)

return

method getMax(dlist = double[]) public static binary returns double

 dmax = Double.MIN_VALUE
 loop n_ = 0 to dlist.length - 1
   if dlist[n_] > dmax then dmax = dlist[n_]
   end n_
 return dmax

method getMax(dlist = Rexx[]) public static binary returns Rexx

 dmax = Rexx(Double.MIN_VALUE)
 loop n_ = 0 to dlist.length - 1
   dmax = dlist[n_].max(dmax)
   end n_
 return dmax

</lang>

Output

Max double:  274.457568703
Max   Rexx:  274.457568703

NewLISP

Nial

The behavior of multi-dimensional arrays is like J

Nimrod

Output:

Objeck

The language has a "Max" method for vectors. <lang objeck> values := IntVector->New([4, 1, 42, 5]); values->Max()->PrintLine(); </lang>

Objective-C

Works with: GNUstep

Works with: Cocoa

This code "extends" (through Objective-C categories) the NSArray adding the method maximumValue; this one iterates over the objects of the collection calling the method compare, if it exists for the object of the collection. Since normally comparing makes sense between numbers, the code also check if the objects being compared are of "kind" NSNumber. If one eliminates this check (substituting it maybe with one that checks if the two object are of the same "kind"), the code is able to get a maximum value for any objects for which make sense a compare method (e.g. strings), that must be implemented.

If there's no a known way of comparing two objects of the collection (or if the objects are not "NSNumber"), the the method return nil (the void object).

<lang objc>#import <Foundation/Foundation.h>

@interface NSArray (WithMaximum) - (id)maximumValue; @end

@implementation NSArray (WithMaximum) - (id)maximumValue {

 if ( [self count] == 0 ) return nil;
 id maybeMax = [self objectAtIndex: 0];
 NSEnumerator *en = [self objectEnumerator];
 id el;
 while ( (el=[en nextObject]) != nil ) {
   if ( [maybeMax respondsToSelector: @selector(compare:)] &&

[el respondsToSelector: @selector(compare:)] && [el isKindOfClass: [NSNumber class]] && [maybeMax isKindOfClass: [NSNumber class]] ) {

     if ( [maybeMax compare: el] == NSOrderedAscending )

maybeMax = el;

   } else { return nil; }
 }
 return maybeMax;

} @end</lang>

This example mixes integers with a double value, just to show that everything is fine until they are NSNumber.

<lang objc>int main() {

 NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 NSArray *collection = [NSArray arrayWithObjects:

[NSNumber numberWithInt: 1], [NSNumber numberWithInt: 2], [NSNumber numberWithInt: 10], [NSNumber numberWithInt: 5], [NSNumber numberWithDouble: 10.5], nil];

 NSLog(@"%@", [collection maximumValue]);
 [pool release];
 return 0;

}</lang>

OCaml

<lang ocaml>let my_max = function

   [] -> invalid_arg "empty list"
 | x::xs -> List.fold_left max x xs</lang>

# my_max [4;3;5;9;2;3] ;;
- : int = 9

Octave

Octave's max accepts a vector (and can return also the index of the maximum value in the vector)

ooRexx

version

<lang ooRexx> -- routine that will work with any ordered collection or sets and bags containing numbers.

routine listMax

 use arg list 
 items list~makearray   -- since we're dealing with different collection types, reduce to an array
 if items~isEmpty then return .nil   -- return a failure indicator.  could also raise an error, if desired
 largest = items[1]

 -- note, this method does call max one extra time.  This could also use the 
 -- do i = 2 to items~size to avoid this
 do item over items 
    largest = max(item, largest) 
 end

 return largest

</lang>

version 2 works with any strings

<lang>/* REXX ***************************************************************

30.07.2013 Walter Pachl as for REXX
- - - - /

s=.list~of('Walter','lives','in','Vienna') say listMax(s) -- routine that will work with any ordered collection or sets and bags.

routine listMax

 use arg list
 items=list~makearray   -- since we're dealing with different collection types, reduce to an array
 if items~isEmpty then return .nil   -- return a failure indicator.  could also raise an error, if desired
 largest = items[1]
 -- note, this method uses one extra comparison.  It could use
 -- do i = 2 to items~size to avoid this
 do item over items
    If item>>largest Then
      largest = item
 end
 return largest</lang>

Oz

<lang oz>declare

 fun {Maximum X|Xr}         %% pattern-match on argument to make sure the list is not empty
    {FoldL Xr Value.max X}  %% fold the binary function Value.max over the list
 end

in

 {Show {Maximum [1 2 3 4 3]}}</lang>

PARI/GP

<lang parigp>vecmax(v)</lang>

Pascal

See Delphi

Perl

<lang perl>sub max {

   my $max = shift;
   for (@_) { $max = $_ if $_ > $max }
   return $max;

}</lang>

It is already implemented in the module List::Util's max() function: <lang perl>use List::Util qw(max);

max(@values);</lang>

Perl 6

The "Any" class defines a max function that can be called either as a method or a subroutine.

Output:

PHP

The built-in PHP function max() already does this. <lang php>max($values)</lang>

PicoLisp

<lang PicoLisp>: (max 2 4 1 3) # Return the maximal argument -> 4

(apply max (2 4 1 3)) # Apply to a list

-> 4

(maxi abs (2 -4 -1 3)) # Maximum according to given function

-> -4</lang>

PL/I

<lang PL/I> maximum = A(lbound(A,1)); do i = lbound(A,1)+1 to hbound(A,1);

 if maximum < A(i) then maximum = A(i);

end; </lang>

PostScript

Ghostscript has a max built-in:

Works with: Ghostscript

<lang postscript>/findmax {

 dup 0 get exch    % put the first element underneath the array
 {max} forall      % replace it by the respective larger value if necessary

} def</lang>

If not using Ghostscript this gets a bit longer:

<lang postscript>/findmax {

 dup 0 get exch    % put the first element underneath the array
 {
   dup             % duplicate the current item
   2 index         % duplicate the current maximum value
   gt              % if the current item is larger
   {exch} if       % swap the two items so the previous maximum is now the top of the stack
   pop             % remove it
 } forall

} def</lang>

Library: initlib

<lang postscript> [1 2 3 4 5 4 3 2 1] uncons exch {max} fold </lang>

PowerBASIC

<lang powerbasic>FUNCTION PBMAIN()

   DIM x AS LONG, y AS LONG, z AS LONG
   RANDOMIZE TIMER

   FOR x = 1 TO 10
       y = INT(RND * 10000)
       z = MAX(y, z)
   NEXT

   ? STR$(z) & " was the highest value"

END FUNCTION</lang>

Sample output:

8104 was the highest value

PowerShell

The Measure-Object cmdlet in PowerShell already has this capability: <lang powershell>function Get-Maximum ($a) {

   return ($a | Measure-Object -Maximum).Maximum

}</lang>

Prolog

SWI-Prolog already knows max_list. <lang Prolog> ?- max_list([1, 2, 10, 3, 0, 7, 9, 5], M). M = 10.</lang>

can be implemented like this:

<lang Prolog> max_list([H|T], Max) :- max_list(T, H, Max).

max_list([], Max, Max).

max_list([H|T], Max0, Max) :- H > Max0, !, max_list(T, H, Max).

max_list([_|T], Max0, Max) :- max_list(T, Max0, Max).

</lang>

PureBasic

<lang PureBasic>Procedure.f Max (Array a.f(1))

  Protected last, i, ret.f

  ret = a(0)   
  last = ArraySize(a())
  For i = 1 To last
     If ret < a(i)
        ret = a(i)
     EndIf
  Next
  
  ProcedureReturn ret

EndProcedure</lang>

Python

The built-in Python function max() already does this. <lang python>max(values)</lang>

Of course this assumes we have a list or tuple (or other sequence like object). (One can even find the max() or min() character of a string since that's treated as a sequence of characters and there are "less than" and "greater than" operations (object methods) associate with those characters).

If we truly were receiving a stream of data then in Python, such streams are usually iterable, meaning they have a way of generating one item at a time from the stream.

max(), (and min()), can take iterables and a key argument which takes a function that can transform each item into a type that we can compare, for example, if the stream were returning string representations of integers, one to a line, you could do <lang python>>>> floatstrings = ['1\n', ' 2.3\n', '4.5e-1\n', '0.01e4\n', '-1.2'] >>> max(floatstrings, key = float) '0.01e4\n' >>></lang> Normally we would want the converted form as the maximum and we could just as easily write: <lang python>>>> max(float(x) for x in floatstrings) 100.0 >>></lang>

R

Racket

The "max" function it built in and takes an arbitrary amount of arguments. <lang racket>(max 12 9 8 17 1)</lang> Outputs:

To use with a list, there is apply: <lang racket>(apply max '(12 9 8 17 1))</lang>

However, if you want to write the function yourself: <lang racket> (define (my-max l)

 (define (max-h l greatest)
   (cond [(empty? l) greatest]
         [(> (first l) greatest) (max-h (rest l) (first l))]
         [else (max-h (rest l) greatest)]))
 (if (empty? l) empty (max-h l (first l))))

</lang>

or with a "for" loop: <lang racket> (define (my-max l)

 (for/fold ([max #f]) ([x l])
   (if (and max (> max x)) max x)))

</lang>

Rascal

Rascal has a built-in function that gives the greatest element of a list <lang rascal> rascal>import List; ok

rascal>max([1,2,3,4]); int: 4 </lang>

Raven

<lang Raven>[ 1 2 3 4 ] max "%d\n" print</lang>

Output:

Randomly generated list size and elements <lang Raven>100 choose as $cnt [ ] as $lst 0 $cnt 1 range each drop 100 choose $lst push $lst print $lst max "max value: %d\n" print</lang>

REBOL

<lang REBOL>REBOL [

   Title: "Maximum Value"
   Date: 2009-12-15
   Author: oofoe
   URL: http://rosettacode.org/wiki/Maximum_Value

]

max: func [ "Find maximum value in a list." values [series!] "List of values." ] [ first maximum-of values ]

print ["Max of" mold d: [5 4 3 2 1] "is" max d] print ["Max of" mold d: [-5 -4 -3 -2 -1] "is" max d]</lang>

Output:

Max of [5 4 3 2 1] is 5
Max of [-5 -4 -3 -2 -1] is -1

REXX

The numbers in the list may be any valid REXX number (integer, negative, floating point, etc.)

using a list

<lang rexx>/*REXX program finds the greatest element in a list (of numbers). */

                            /* [↓] list of first twenty reversed primes*/

y = '2 3 5 7 11 31 71 91 32 92 13 73 14 34 74 35 95 16 76 17'

big = word(y,1) /*choose a initial biggest number*/

                do j=2  to words(y)   /*traipse through the list.      */
                big = max(big, word(y,j))
                end   /*j*/

say 'the biggest value in a list of' words(y) "numbers is:" big

                                      /*stick a fork in it, we're done.*/</lang>

output

the biggest value in a list of 20 numbers is: 95

using an array

<lang rexx>/*REXX program finds the greatest element in an array (of numbers). */ y.1 = 2; y.2 = 3; y.3 = 5; y.4 = 7; y.5 = 11 y.6 = 31; y.7 = 71; y.8 = 91; y.9 = 32; y.10 = 92 y.11 = 13; y.12 = 73; y.13 = 14; y.14 = 34; y.15 = 74 y.16 = 35; y.17 = 95; y.18 = 16; y.19 = 76; y.20 = 17

big = y.1 /*choose a initial biggest number*/ items = 20 /*number of elements in the array*/

               do j=2  to items       /*traipse through the array.     */
               big = max(big, y.j)    /*use a BIF for finding the max. */
               end   /*j*/

say 'the biggest value in an array of' items "elements is:" big

                                      /*stick a fork in it, we're done.*/</lang>

output

the biggest value in an array of 20 elements is: 95

list of any strings

<lang rexx>/* REXX ***************************************************************

If the list contains any character strings, the following will wotk
Note the use of >> (instead of >) to avoid numeric comparison
30.07.2013 Walter Pachl
- - - - /

list='Walter Pachl living in Vienna' Say max(list) list='8 33 -12' Say max(list) Exit max: Procedure Parse Arg l max=word(l,1) Do i=2 To words(l)

 If word(l,i)>>max Then
   max=word(l,i)
 End

Return max</lang> Output (PC):

living
8

output when using a list which is: 12 111111 1 (lexigraphically 12 is greater than 111111)

Ruby

max is a method of all Enumerables <lang ruby>values.max</lang>

Run BASIC

<lang Runbasic>list$= "1 12 -55 46 41 3.66 19" while word$(list$,i+1," ") <> ""

 mx = max(mx,val(word$(list$,i+1," ")))
 i = i + 1

wend print mx</lang>

Scala

Library: Scala

<lang Scala>def noSweat(list: Int*) = list.max // Test assert(noSweat(1, 3, 12, 7) == 12)</lang>

Scheme

The built-in Scheme function max takes the max of all its arguments. <lang scheme>(max 1 2 3 4) (apply max values) ; find max of a list</lang>

Seed7

<lang seed7>$ include "seed7_05.s7i";

const func integer: max (in array integer: values) is func

 result
   var integer: max is 0;
 local
   var integer: index is 0;
 begin
   max := values[1];
   for index range 2 to length(values) do
     if values[index] > max then
       max := values[index];
     end if;
   end for;
 end func;

const proc: main is func

 begin
   writeln(max([] (1, 2, 6, 4, 3)));
 end func;</lang>

Output:

Slate

<lang slate>#(1 2 3 4 20 10 9 8) reduce: [| :a :b | a max: b]</lang>

Smalltalk

Using fold it is very simple to find the maximum value among a collection.

<lang smalltalk>#(1 2 3 4 20 10 9 8) fold: [:a :b | a max: b] "returns 20"</lang>

Or, since it's "built-in", you can simply do:

Works with: Pharo version 1.4

Works with: Smalltalk/X

<lang smalltalk>#(1 2 3 4 20 10 9 8) max. "returns 20"</lang>

SNOBOL4

<lang snobol4>while a = trim(input) :f(stop)

       max = gt(a,max) a   :(while)

stop output = max end</lang>

Standard ML

Comparisons are specific for each type. Here is a max function for a list of ints: <lang sml>fun max_of_ints [] = raise Empty

 | max_of_ints (x::xs) = foldl Int.max x xs</lang>

- max_of_ints [4,3,5,9,2,3];
val it = 9 : int

Tcl

Works with: Tcl version 8.5

Use the {*} expansion operator to substitute the list value with its constituent elements <lang tcl>package require Tcl 8.5

set values {4 3 2 7 8 9}

tcl::mathfunc::max {*}$values ;# ==> 9</lang>

TI-89 BASIC

The builtin max function can be applied to lists. max({1, 3, 2}) = 3.

Trith

<lang trith>[1 -2 3.1415 0 42 7] [max] foldl1</lang>

TUSCRIPT

<lang tuscript> $$ MODE TUSCRIPT LOOP n,list="2'4'0'3'1'2'-12" IF (n==1) greatest=VALUE(list) IF (list>greatest) greatest=VALUE(list) ENDLOOP PRINT greatest </lang> Output:

UNIX Shell

Works with: bash version 3

Works with: pdksh

<lang bash>max() {

 local m=$1
 shift
 while [ $# -gt 0 ]
 do
   [ "$m" -lt "$1" ] && m=$1
   shift
 done
 echo "$m"

}

max 10 9 11 57 1 12</lang>

Works with: Bourne Shell

<lang bash>max() {

 m=$1  # Bourne Shell has no local command.
 shift
 while [ $# -gt 0 ]
 do
   [ "$m" -lt "$1" ] && m=$1
   shift
 done
 echo "$m"

}</lang>

Ursala

The built-in $^ operator takes a binary predicate of any type to a function extracting the maximum value from a non-empty list of that type. In this case it is used with fleq, the partial order relation on floating point numbers. <lang Ursala>#import flo

cast %e

example = fleq$^ <-1.,-2.,0.,5.,4.,6.,1.,-5.></lang> output:

6.000000e+00

V

Assuming it is a list of positive numbers <lang v>[4 3 2 7 8 9] 0 [max] fold =9</lang>

If it is not <lang v>[4 3 2 7 8 9] dup first [max] fold</lang>

=9

Visual Basic

<lang vb>Public Function ListMax(anArray())

   'return the greatest element in array anArray
   'use LBound and UBound to find its length
   n0 = LBound(anArray)
   n = UBound(anArray)
   theMax = anArray(n0)
   For i = (n0 + 1) To n
       If anArray(i) > theMax Then theMax = anArray(i)
   Next
   ListMax = theMax

End Function

Public Sub ListMaxTest()

   Dim b()
   'test function ListMax
   'fill array b with some numbers:
   b = Array(5992424433449#, 4534344439984#, 551344678, 99800000#)
   'print the greatest element
   Debug.Print "Greatest element is"; ListMax(b())

End Sub</lang>

Result:

ListMaxTest
Greatest element is 5992424433449

XPL0

The set of values is the lengths of the lines of text in the input file.

<lang XPL0>include c:\cxpl\codes; \include 'code' declarations

def Tab=$09, LF=$0A, CR=$0D, EOF=$1A;

int CpuReg, Hand; char CmdTail($80); int I, Max, C;

[\Copy file name on command line, which is in the Program Segment Prefix (PSP) \ ES=CpuReg(11), to the CmdTail array, which is in our Data Segment = CpuReg(12) CpuReg:= GetReg; \point to copy of CPU registers Blit(CpuReg(11), $81, CpuReg(12), CmdTail, $7F); Hand:= FOpen(CmdTail, 0); \open file for input and get its handle FSet(Hand, ^I); \assign handle to device 3 OpenI(3); \initialize file for input

Max:= 0; \scan file for longest line repeat I:= 0;

       repeat  C:= ChIn(3);
               case C of
                 CR, LF, EOF:  [];     \don't count these characters
                 Tab:  [I:= I+8 & ~7]  \(every 8th column)
               other   I:= I+1;        \count all other characters
       until   C=LF or C=EOF;
       if I > Max then Max:= I;

until C = EOF; Text(0, "Longest line = "); IntOut(0, Max); CrLf(0); ]</lang>

Example of running the program on its source code:

maxline maxline.xpl
Longest line = 80

Yorick

The built-in function max does this. Interactive example:

> foo = [4, 3, 2, 7, 8, 9]
> max(foo)
9

@@ Line 1,173: / Line 1,173: @@
 <lang nial>max 1 2 3 4
 =4</lang>
+=={{header|Nimrod}}==
+<lang Nimrod>echo max([2,3,4,5,6,1])</lang>
+{{out}}<pre>6</pre>
 =={{header|Objeck}}==

Revision as of 20:29, 1 August 2013

CSV Data

Pseudo-arrays

True arrays

Applying a function to each element of an array

More trivial example

Icon and Unicon

version

version 2 works with any strings

using a list

using an array

list of any strings