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<article><h2>Ruby mode</h2><form><textarea id="code" name="code"># Code from http://sandbox.mc.edu/~bennet/ruby/code/poly_rb.html## This program evaluates polynomials. It first asks for the coefficients# of a polynomial, which must be entered on one line, highest-order first.# It then requests values of x and will compute the value of the poly for# each x. It will repeatly ask for x values, unless you the user enters# a blank line. It that case, it will ask for another polynomial. If the# user types quit for either input, the program immediately exits.#
## Function to evaluate a polynomial at x. The polynomial is given# as a list of coefficients, from the greatest to the least.def polyval(x, coef) sum = 0 coef = coef.clone # Don't want to destroy the original while true sum += coef.shift # Add and remove the next coef break if coef.empty? # If no more, done entirely. sum *= x # This happens the right number of times. end return sumend
## Function to read a line containing a list of integers and return# them as an array of integers. If the string conversion fails, it# throws TypeError. If the input line is the word 'quit', then it# converts it to an end-of-file exceptiondef readints(prompt) # Read a line print prompt line = readline.chomp raise EOFError.new if line == 'quit' # You can also use a real EOF. # Go through each item on the line, converting each one and adding it # to retval. retval = [ ] for str in line.split(/\s+/) if str =~ /^\-?\d+$/ retval.push(str.to_i) else raise TypeError.new end end
return retvalend
## Take a coeff and an exponent and return the string representation, ignoring# the sign of the coefficient.def term_to_str(coef, exp) ret = ""
# Show coeff, unless it's 1 or at the right coef = coef.abs ret = coef.to_s unless coef == 1 && exp > 0 ret += "x" if exp > 0 # x if exponent not 0 ret += "^" + exp.to_s if exp > 1 # ^exponent, if > 1.
return retend
## Create a string of the polynomial in sort-of-readable form.def polystr(p) # Get the exponent of first coefficient, plus 1. exp = p.length
# Assign exponents to each term, making pairs of coeff and exponent, # Then get rid of the zero terms. p = (p.map { |c| exp -= 1; [ c, exp ] }).select { |p| p[0] != 0 }
# If there's nothing left, it's a zero return "0" if p.empty?
# *** Now p is a non-empty list of [ coef, exponent ] pairs. ***
# Convert the first term, preceded by a "-" if it's negative. result = (if p[0][0] < 0 then "-" else "" end) + term_to_str(*p[0])
# Convert the rest of the terms, in each case adding the appropriate # + or - separating them. for term in p[1...p.length] # Add the separator then the rep. of the term. result += (if term[0] < 0 then " - " else " + " end) + term_to_str(*term) end
return resultend ## Run until some kind of endfile.begin # Repeat until an exception or quit gets us out. while true # Read a poly until it works. An EOF will except out of the # program. print "\n" begin poly = readints("Enter a polynomial coefficients: ") rescue TypeError print "Try again.\n" retry end break if poly.empty?
# Read and evaluate x values until the user types a blank line. # Again, an EOF will except out of the pgm. while true # Request an integer. print "Enter x value or blank line: " x = readline.chomp break if x == '' raise EOFError.new if x == 'quit'
# If it looks bad, let's try again. if x !~ /^\-?\d+$/ print "That doesn't look like an integer. Please try again.\n" next end
# Convert to an integer and print the result. x = x.to_i print "p(x) = ", polystr(poly), "\n" print "p(", x, ") = ", polyval(x, poly), "\n" end endrescue EOFError print "\n=== EOF ===\n"rescue Interrupt, SignalException print "\n=== Interrupted ===\n"else print "--- Bye ---\n"end</textarea></form> <script> var editor = CodeMirror.fromTextArea(document.getElementById("code"), { mode: "text/x-ruby", matchBrackets: true, indentUnit: 4 }); </script>
<p><strong>MIME types defined:</strong> <code>text/x-ruby</code>.</p>
<p>Development of the CodeMirror Ruby mode was kindly sponsored by <a href="http://ubalo.com/">Ubalo</a>.</p>
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