############################################################################
#
#       File:     polydemo.icn
#
#       Subject:  Program to demonstrate polynomial library
#
#       Author:   Erik Eid
#                         
#       Date:     May 23, 1994
#
############################################################################
#
#   This file is in the public domain.
#
############################################################################
#
#     This program is an example for the use of the polystuf library.  The
# user is given a number of options that allow the creation, output,
# deletion, or operations on up to 26 polynomials, indexed by letter.
#
# Available commands:
#     (R)ead      - allows input of a polynomial by giving pairs of
#                   coefficients and exponents.  For example, entering
#                   5, 6, 2, and 3 will create 5x^6 + 2x^3.  This polynomial
#                   will be stored by an index which is a lower-case letter.
#     (W)rite     - outputs to the screen a chosen polynomial.
#     (A)dd       - adds two polynomials and defines the sum as a third
#     (S)ubtract  - subtracts two polynomials and defines the difference as
#                   a third.
#     (M)ultiply  - multiplies two polynomials and defines the product as a
#                   third.
#     (E)valuate  - gives the result of setting x in a polynomial to a value
#     (C)lear     - deletes one polynomial
#     (H)elp      - lists all commands
#     (Q)uit      - end the demonstration
#
############################################################################
#
#  Links: polystuf
#
############################################################################

link polystuf

global filled, undefined, poly_table

procedure main()
local option
  poly_table := table()                    # Set up a table that will hold
                                           # all of the polynomials (which
                                           # are tables themselves).
  filled := "That slot is already filled!"
  undefined := "That has not been defined!"
  SetUpDisplay()
  repeat {
    ShowInUse()
    writes ("RWASMECHQ> ")
    option := choice(read())               # Get first letter of entry in
                                           # lower-case format.
    case option of {
      "r": PRead()
      "w": PWrite()
      "a": PCalc ("+")
      "s": PCalc ("-")
      "m": PCalc ("*")
      "e": PEval()
      "c": PClear()
      "h": ShowHelp()
      "q": break
      default: write ("Invalid command!")
    }
    write()
  }
end

procedure SetUpDisplay()
  write (center ("Icon v8.10 Polynomial Demo", 80))
  write()
  ShowHelp()
  write (repl("-", 80))
  return
end

procedure ShowHelp()
  write (repl(" ", 10), "(R)ead      (W)rite     (A)dd       (S)ubtract")
  write (repl(" ", 10), "(M)ultiply  (E)valuate  (C)lear     _
    (H)elp      (Q)uit")
  return
end

procedure ShowInUse()
local keylist
  keylist := list()
  writes ("In Use:")
  every push (keylist, key(poly_table))    # Construct a list of the keys in
                                           # poly_table, corresponding to
                                           # which slots are being used.
  keylist := sort (keylist)
  every writes (" ", !keylist)
  write()
  return
end

procedure is_lower(c)
  if /c then fail
  if c == "" then fail
  return (c >>= "a") & (c <<= "z")         # Succeeds only if c is a lower-
end                                        # case letter.

procedure choice(s)
  return map(s[1], &ucase, &lcase)         # Returns the first character of
                                           # the given string converted to
                                           # lower-case.
end

procedure PRead()
local slot, terms, c, e
  repeat {
    writes ("Which slot to read into? ")
    slot := choice(read())
    if is_lower(slot) then break
  }
  if member (poly_table, slot) then {      # Disallow reading into an
    write (filled)                         # already occupied slot.
    fail
  }
  write ("Input terms as coefficient-exponent pairs.  Enter 0 for")
  write ("coefficient to stop.  Entries must be numerics.")
  terms := list()
  repeat {
    write()
    repeat {
      writes ("Coefficient> ")     
      c := read()
      if numeric(c) then break
    }
    if c = 0 then break
    repeat {
      writes ("   Exponent> ")     
      e := read()
      if numeric(e) then break
    }
    put (terms, c)                         # This makes a list compatible
    put (terms, e)                         # with the format needed by
                                           # procedure poly of polystuf.
  }
  if *terms = 0 then terms := [0, 0]       # No terms = zero polynomial.
  poly_table[slot] := poly ! terms         # Send the elements of terms as
                                           # parameters to poly and store
                                           # the resulting polynomial in the
                                           # proper slot.
  return
end

procedure PWrite ()
local slot
  repeat {
    writes ("Which polynomial to display? ")
    slot := choice(read())
    if is_lower(slot) then break
  }
  if member (poly_table, slot) then {      # Make sure there is a polynomial
    write (poly_string(poly_table[slot]))  # to write!
    return
  }
  else {
    write (undefined)
    fail
  }
end

procedure PCalc (op)
local slot1, slot2, slot_ans, res
  writes ("Which two polynomials to ")
  case op of {
    "+": write ("add? ")                   # Note that this procedure is
    "-": write ("subtract? ")              # used for all three operations
    "*": write ("multiply? ")              # since similar tasks, such as
  }                                        # checking on the status of slots,
                                           # are needed for all of them.
  repeat {
    writes ("First: ")     
    slot1 := choice(read())
    if is_lower(slot1) then break
  }
  if member (poly_table, slot1) then {
    repeat {
      writes ("Second: ")     
      slot2 := choice(read())
      if is_lower(slot2) then break
    }
    if member (poly_table, slot2) then {
      repeat {
        writes ("Slot for answer: ")     
        slot_ans := choice(read())
        if is_lower(slot_ans) then break
      }
      if member (poly_table, slot_ans) then {
        write (filled)     
        fail
      }
      else {
        case op of {
          "+": {
            res := poly_add(poly_table[slot1], poly_table[slot2])
            writes ("Sum ")
          }
          "-": {
            res := poly_sub(poly_table[slot1], poly_table[slot2])
            writes ("Difference ")
          }
          "*": {
            res := poly_mul(poly_table[slot1], poly_table[slot2])
            writes ("Product ")
          }
        }
        write ("has been defined as polynomial \"", slot_ans, "\"")
        poly_table[slot_ans] := res
      }
    }
    else {
      write (undefined)     
      fail
    }
  }
  else {
    write (undefined)     
    fail
  }
  return
end

procedure PEval ()
local slot, x, answer
  repeat {
    writes ("Which polynomial to evaluate? ")
    slot := choice(read())
    if is_lower(slot) then break
  }
  if member (poly_table, slot) then {
    repeat {
      writes ("What positive x to evaluate at? ")
      x := read()
      if numeric(x) then if x > 0 then break
    }
    answer := poly_eval (poly_table[slot], x)
    write ("The result is ", answer)
    return
  }
  else {
    write (undefined)     
    fail
  }
end

procedure PClear ()
local slot
  repeat {
    writes ("Which polynomial to clear? ")
    slot := choice(read())
    if is_lower(slot) then break
  }
  if member (poly_table, slot) then {
    delete (poly_table, slot)
    return
  }
  else {
    write (undefined)     
    fail
  }
end