1 | // $Id: factor.lib,v 1.4 1998-04-03 22:47:01 krueger Exp $ |
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2 | //(RS) |
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3 | /////////////////////////////////////////////////////////////////////////////// |
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4 | |
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5 | version="$Id: factor.lib,v 1.4 1998-04-03 22:47:01 krueger Exp $"; |
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6 | info=" |
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7 | LIBRARY: factor.lib PROCEDURES FOR CALLING THE REDUCE FACTORIZER |
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8 | |
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9 | delete_dollar(s) return the string s with '$' deleted |
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10 | reduce_factor(f) list of factors of f, calling REDUCE (UNIX only) |
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11 | "; |
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12 | |
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13 | /////////////////////////////////////////////////////////////////////////////// |
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14 | |
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15 | proc delete_dollar ( string s ) |
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16 | USAGE: delete_dollar(s); s = string |
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17 | RETURN: string, with '$' replaced by ' ' |
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18 | EXAMPLE: example delete_dollar; shows an example |
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19 | { |
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20 | while( s[size(s)]=="$" and size(s)!=1 ) { s=s[1,size(s)-1]; } |
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21 | while( s[1]=="$" and size(s)!=1 ) { s=s[2,size(s)-1]; } |
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22 | if( size(s)==1 and s[1]=="$" ) { return(""); } |
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23 | int i=find(s,"$"); |
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24 | while( i!=0 ) |
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25 | { |
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26 | s=s[1,i-1]+s[i+1,size(s)-i]; |
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27 | i=find(s,"$"); |
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28 | } |
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29 | return(s); |
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30 | } |
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31 | example |
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32 | { "EXAMPLE:"; echo = 2; |
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33 | string s = "123$456$"; |
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34 | delete_dollar(s); |
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35 | delete_dollar(s)+"789"; |
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36 | } |
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37 | /////////////////////////////////////////////////////////////////////////////// |
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38 | |
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39 | proc reduce_factor ( poly f ) |
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40 | USAGE: reduce_factor(f); f = poly |
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41 | RETURN: list, the factors of f |
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42 | NOTE: due to a limitation of REDUCE, multivariate polynomials can only |
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43 | be factorized in characteristic 0 |
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44 | This proc runs under UNIX only |
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45 | EXAMPLE: example reduce_factor; shows an example |
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46 | { |
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47 | string pid = string( system( "pid" ) ); |
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48 | string outname = "/tmp/singred." + pid + ".out"; |
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49 | string scriptname = "/tmp/singred." + pid + ".sh"; |
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50 | int n = char( basering ); |
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51 | int shortOutput = short; |
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52 | short = 0; |
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53 | write (scriptname,"#!/bin/sh |
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54 | $reduce/reduce >/dev/null <<EOF |
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55 | off nat$ off echo$ setmod " + string( n ) + "$ |
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56 | erg:=factorize(",f,")$ |
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57 | out \"" + outname + "\"$ |
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58 | write(\"list result;\")$ |
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59 | counter:=1$ |
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60 | for each a in erg do begin |
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61 | write(\"result[\",counter,\"]=\",a,\";\"); |
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62 | counter:=counter+1; |
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63 | end; |
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64 | shut \"" + outname + "\"; |
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65 | quit$ |
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66 | EOF"); |
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67 | system( "sh", "chmod 700 " + scriptname ); |
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68 | system( "sh", scriptname ); |
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69 | string resultstring = read( outname ); |
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70 | if ( resultstring <> "" ) |
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71 | { |
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72 | resultstring = delete_dollar( resultstring ); |
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73 | execute resultstring; |
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74 | } |
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75 | // remove tmp-files after usage */ |
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76 | system( "sh", "/bin/rm " + outname ); |
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77 | system( "sh", "/bin/rm " + scriptname ); |
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78 | short = shortOutput; |
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79 | return( result ); |
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80 | } |
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81 | example |
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82 | { "EXAMPLE:"; echo = 2; |
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83 | ring r=0,(x,y,z),lp; |
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84 | poly f=(x+y)*(y+z)^2*(z+x); |
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85 | f; |
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86 | list L=reduce_factor(f); |
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87 | L; |
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88 | } |
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