とある数字をとある範囲にスケールする

/*
 float m = map(value, 0, 100, 0, width);
 
 Re-maps a number from one range to another. 
 In the example above, the number '25' is converted from a value 
 in the range 0..100 into a value that ranges from the left edge (0) to 
 the right edge (width) of the screen. 
 */
-(float)map:(float)value currLow:(float)currLow currHigh:(float)currHigh tarLow:(float)tarLow tarHigh:(float)tarHigh{
    return tarLow + (tarHigh - tarLow) * ((value - currLow) / (currHigh - currLow));
}