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Annotation of researchv10dc/cmd/icon/ipl/source/parens.icn, revision 1.1

1.1     ! root        1: #      PARENS
        !             2: #
        !             3: #      Produce parenthesis-balanced strings
        !             4: #
        !             5: #      Ralph E. Griswold
        !             6: #
        !             7: #      Last modified 8/11/84
        !             8: #
        !             9: 
        !            10: global r, k, lp, rp
        !            11: 
        !            12: procedure main(a)
        !            13:    local string, i, s, bound, limit, varying
        !            14:    bound := limit := 10                        # default bound and limit
        !            15:    lp := "("                           # default left paren
        !            16:    rp := ")"                           # default right paren
        !            17:    i := 0
        !            18:    while s := a[i +:= 1] do
        !            19:       if s[1] == "-" then
        !            20:          case s of {
        !            21:             "-b":   bound := integer(a[i +:= 1]) | Usage()     # bound
        !            22:             "-n":   limit := integer(a[i +:= 1]) | Usage()     # total number
        !            23:             "-l":   lp := a[i +:= 1] | Usage()                 # left paren
        !            24:             "-r":   rp := a[i +:= 1] | Usage()                 # right paren
        !            25:             "-v":   varying := 1                               # varying length
        !            26:             default: Usage()
        !            27:             }
        !            28:       else Usage()
        !            29:    every 1 to limit do {
        !            30:       if \varying then k := 2 * ?bound else k := 2 * bound
        !            31:       string := ""
        !            32:       r := 0
        !            33:       while k ~= r do {
        !            34:          if r = 0 then string ||:= Open()
        !            35:          else if ?0 < probClose()
        !            36:             then string ||:= Close() else string ||:= Open()
        !            37:          }
        !            38:       while k > 0 do string ||:= Close()
        !            39:       write(string)
        !            40:       }
        !            41: end
        !            42: 
        !            43: procedure Open()
        !            44:    r +:= 1
        !            45:    k -:= 1
        !            46:    return lp
        !            47: end
        !            48: 
        !            49: procedure Close()
        !            50:    r -:= 1
        !            51:    k -:= 1
        !            52:    return rp
        !            53: end
        !            54: 
        !            55: procedure probClose()
        !            56:    return ((r * (r + k + 2)) / (2.0 * k * (r + 1)))
        !            57: end
        !            58: 
        !            59: procedure Usage()
        !            60:    stop("usage: parens [-v -n i -b i -l s -r s]")
        !            61: end

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