# Prints a histogram for a distribution of letter grades computed 
# from a collection of numeric grades extracted from a text file.  

from maphist import Histogram

def main():
   # Create a Histogram instance for computing the frequencies.
  gradeHist = Histogram( "ABCDF" )
  
   # Open the text file containing the grades.
  gradeFile = open('cs204grades.txt', "r")
#  gradeFile = open('authorexample.txt', "r")
  
   # Extract the grades and increment the appropriate counter.
  for line in gradeFile :
    grade = int(line)
    gradeHist.incCount( letterGrade(grade) )

   # Print the histogram chart.
  printChart( gradeHist )  
        
# Determines the letter grade for the given numeric value.
def letterGrade( grade ):
  if grade >= 90 :
    return 'A'
  elif grade >= 80 :
    return 'B'
  elif grade >= 70 :
    return 'C'
  elif grade >= 60 :
    return 'D'
  else :
    return 'F'
 
# Prints the histogram as a horizontal bar chart.  
def printChart( gradeHist ):
  print( "           Grade Distribution" )  
   # Print the body of the chart.
  letterGrades = ( 'A', 'B', 'C', 'D', 'F' )
  for letter in letterGrades :
    print( "  |" )
    print( letter + " +", end = "" )
    freq = gradeHist.getCount( letter )
    print( '*' * freq )
  
   # Print the x-axis.
  print( "  |" )
  print( "  +----+----+----+----+----+----+----+----" )
  print( "  0    5    10   15   20   25   30   35" )
    
# Calls the main routine.  
main()