DZone Snippets: map code

mapi: similar to standard map in Scheme, but function has index of elements as second parameter.

sumimus (Sumimus L) — Wed, 16 Apr 2008 22:03:41 GMT



;;;  mapi: similar to standard map in Scheme, but function has index of elements as parameter.

;;;

(define (mapi p l)

  (let loop ((l l) (i 0) (r '()))

    (if (pair? l)

	(loop (cdr l) (+ i 1) (cons (p (car l) i) r))

	(reverse r))))



;; Example: converting a binary number given as a list of binary digits. 

;; (apply + (mapi (lambda (x i) (* x (expt 2 i))) '(0 1 1)))

;; => 6

Printing out a Map in sorted order

Archanciel (Jean-Pierre Schnyder) — Thu, 27 Mar 2008 09:09:50 GMT

// print out a Map in sorted order of its keys



    public static String dumpToString(Map map) {

        if (map == null) {

            return Constants.EMPTY_STRING;

        }



        StringBuffer strbuf = new StringBuffer();



        SortedMap sMap = new TreeMap(map);

        Set> s = sMap.entrySet();



        for (Map.Entry elem : s) {

            String key = elem.getKey();

            Object value = elem.getValue();

            strbuf.append(key);

            strbuf.append("=");

            strbuf.append(value == null ? Constants.EMPTY_STRING : value);

            strbuf.append("\r\n");

        }



        return strbuf.toString();

    }

R3 compatible MAP

gregg.irwin (Gregg Irwin) — Fri, 29 Feb 2008 05:36:32 GMT

; Not terrribly efficient, but it works.



    ; R3-compatible interface

    map: func ['word data [block!] body [block!]] [

        collect/only res compose/deep [

            repeat (word) data [res: do bind/copy body (to lit-word! word)]

        ]

    ]

In-place map_with_index

vinterbleg (Simon Ask Ulsnes) — Fri, 08 Feb 2008 10:29:44 GMT

// This code is similar to Enumerable#map, but like each_with_index, it also yields the index of the current element.



class Array

    def map_with_index!

       each_with_index do |e, idx| self[idx] = yield(e, idx); end

    end



    def map_with_index(&block)

        dup.map_with_index!(&block)

    end

end

Recursively dump imbricated Map of Maps

Archanciel (Jean-Pierre Schnyder) — Wed, 12 Sep 2007 12:58:09 GMT

// description of your code here



    public void dumpMapOfMap(Map map) {

        Set s = map.entrySet();

        Iterator sit = s.iterator();

        boolean isFirst = true;



        while (sit.hasNext()) {

            Map.Entry elem = (Map.Entry)sit.next();

            String key = (String)elem.getKey();

            Object value = elem.getValue();



            if (value instanceof String) {

                // recursivity stop condition

                System.out.print(key);

                System.out.print(" : ");

                System.out.println(value);

            } else {

                if (!isFirst) {

                    System.out.println("");

                } else {

                    isFirst = false;

                }

                System.out.println(key);

                Map valueMap = (Map)elem.getValue();

                dumpMapOfMap(valueMap);

            }

        }

    }

Download coordinate from maproom

lindenb (Pierre) — Thu, 31 May 2007 07:29:53 GMT

// description of your code here



IFS="

"

for C in Africa Antarctica Asia Australasia Europe North_America South_America

do

	mkdir -p GIS/$C

	wget -O jeter.html -q "http://www.maproom.psu.edu/cgi-bin/dcw/dcwarea.cgi?$C"

	for P in `egrep '^' -f2`

	do

		curl -d "area=$C" -d "country=$P" -o jeter2.html "http://www.maproom.psu.edu/cgi-bin/dcw/dcwcountry0.cgi"

		P2=`grep FORM jeter2.html | grep point10 | tr "<>" "\n\n" | grep count| cut -d ' ' -f4 | cut -d '=' -f2`

		#curl -d "country=$P2" -o jeter3.txt "http://www.maproom.psu.edu/cgi-bin/dcw/point10.cgi"

		wget -O jeter2.html "http://www.maproom.psu.edu/cgi-bin/dcw/point10.cgi?country=$P2"

		P3=`cat  jeter2.html | tr " >" "\n\n" | grep ftp`

		echo "##### $P2 $P3"	

		wget -O jeter3.txt "$P3"

		mv jeter3.txt > GIS/$C/${P2}.js

		sleep 3

	done

done

A sortable, ordered Map

janhoo (Jan Galinski) — Thu, 21 Sep 2006 20:01:44 GMT

This is a neat collection that allows its elements to be sorted arbitary by moving them up and down in the List or put them to a given index. Nice to display lists that can be edited (i.e. reordered) by the user.



import java.util.ArrayList;

import java.util.Collection;

import java.util.Iterator;

import java.util.List;



import org.apache.commons.collections.map.ListOrderedMap;



/**

 * @author janhoo

 */

public class SortableOrderedMap extends ListOrderedMap {



  /**

   * Inserts a given Key/Value-Pair on a certain Position

   * alle following Pairs are moved up accordingly 

   * 

   * @param newKey

   * @param newValue

   * @param pos

   * @return

   */

  public Object putOnPosition(Object newKey, Object newValue, int pos) {

    Object res = put(newKey, newValue);

    while (indexOf(newKey) > pos) {

      moveUp(newKey);

    }

    return res;

  }



  /**

   * Inserts a given Key/Value Pair before position of a given Key

   * 

   * @param newKey

   * @param newValue

   * @param oldKey

   * @return

   */

  public Object putBefore(Object newKey, Object newValue, Object oldKey) {

    if (!containsKey(oldKey)) {

      return put(newKey, newValue);

    }

    return putOnPosition(newKey, newValue, indexOf(oldKey));

  }



  /**

   * 

   * inserts a given key/value pair after the position of a given key

   * 

   * @param newKey

   * @param newValue

   * @param oldKey

   * @return

   */

  public Object putAfter(Object newKey, Object newValue, Object oldKey) {

    if (!containsKey(oldKey)) {

      return put(newKey, newValue);

    }

    return putOnPosition(newKey, newValue, indexOf(oldKey)+1);

  }

	

  /**

   * moves item with given key up by one step. Does nothing

   * if the item is already on top or not existend.

   * 

   * @param the key of the Item to be moved

   */

  public synchronized void moveUp(Object key) {



    // return if already on top or key not in map	

    if (key.equals(firstKey()) || !containsKey(key)) {

      return;

    }

    int pcur = indexOf(key);



    insertOrder.set(pcur, previousKey(key));

    insertOrder.set(pcur - 1, key);

  }



  /**

   * moves item with given key down by one step. Does nothing

   * if the item is already on bottom or not existend.

   * 

   * @param the key of the Item to be moved

   */

  public synchronized void moveDown(Object key) {

    if (key.equals(lastKey()) || !containsKey(key)) {

      return;

    }

    int pcur = indexOf(key);

    insertOrder.set(pcur, nextKey(key));

    insertOrder.set(pcur + 1, key);

  }



  /* (non-Javadoc)

   * @see org.apache.commons.collections.map.ListOrderedMap#asList()

   */

  public List asList() {

    ArrayList v = new ArrayList();

    for (Iterator it = values().iterator(); it.hasNext();) {

      v.add(it.next());

    }

    return v;

  }



	

  /* (non-Javadoc)

   * @see java.lang.Object#toString()

   */

  public String toString() {

    StringBuffer b = new StringBuffer();

    for (Iterator it = values().iterator(); it.hasNext();) {

      b.append(it.next().toString() + "\n");

    }  

    return b.toString();

  }

}

Attention: this requires the jakarta commons collections

map function

gregg.irwin (Gregg Irwin) — Tue, 10 Jan 2006 05:46:22 GMT



; Larry Palmiter

map: func [fn blk args /local result][

	result: copy []

	repeat el blk [append/only result fn :el args]

	return result

]

Lua: Lazy Map Implementation: Round One

kergoth (Chris Larson) — Mon, 05 Dec 2005 16:13:24 GMT

Concept code for a lazy map implementation in Lua

require "std.table" -- For memoize



function map(t, f)

    local nt = table.memoize(function (k) return f(t[k]) end)

    local mt = getmetatable(nt)

    function mt:__pairs()

        local k

        local function mynext()

            k,v = next(t, k)

            if k == nil then return nil end

            return k,nt[k]

        end

        return mynext, self

    end

    return nt

end

Example Usage:

require "std.base" -- For better table tostring()



local mylist = {1,3,5,7,9}

local newlist = map(mylist, function(v) return 3 * v - 2 end)

assert(mylist[3] == 5)

assert(newlist[3] == 13)



require "std.base" -- For the pairs() that obeys the __pairs metamethod

print("old:", mylist)

print("new(3*v-2):", newlist)

Google map pin

korakot (Korakot Chaovavanich) — Sat, 01 Oct 2005 19:11:37 GMT



def pin(x,y,char=None):

    # top-left is x-5, y-17

    points = [ (0,0), (-2,-6), (-5,-10), (-5,-14), (-2,-17), \

                      (2,-17), (5,-14), (5,-10), (2,-6)]

    c.polygon([(x+dx,y+dy) for dx,dy in points], 0, (255,119,107), 1)

    if char:

        c.text((x-2, y-7), unicode(char))

    else:

        c.point((x,y-12), 0, width=5)

Instead of adding a pin image to the program, this function
will draw a google map pin at point (x,y) instead.
If you give it a char, it will put that char in the middle of
the pin as well



pin(20,20,'A') # A in the pin

pin(40,40)  # just bull-eye