Edinburgh IMP77 Compiler - Version 8.4 1 %begin 2 3 {----------------------------------------------------------------------------} 4 ! Convert a floating point number to a string, along the lines of 5 ! +/-nnn.nnn@+/-nn, to occupy Places character spaces 6 ! with sf significant figures. 7 ! Rounding/truncation will occur to ensure sf limits 8 ! 9 ! %longreal f = floating point number to convert to a string 10 ! %integer sf = number of significant figures required 11 ! places = number of characters in converted string 12 ! 13 ! N.B. sf must be in the range of accuracy of %longreal (<15) 14 ! places must be slightly greater than sf 15 ! (to allow for sign and scientific notation) 16 ! sign uses 1 character (+ is omitted) 17 ! decimal point uses 1 character 18 ! scientific notation could use : 19 ! 1 char for "@" ndicating scientific notation 20 ! 1 char for sign of exponent (sign always present) 21 ! 1+ char for integer exponent 22 ! 23 ! N.B. scientific notation is only used if the decimal string could 24 ! not fit in the places required 25 ! 26 ! eg. F to S (0.003999, 3, 7) -> " 0.004 " (note rounding creates zeros after the 4) 27 ! or 28 ! eg. F to S (0.003999, 3, 4) -> " 4.00@-3" (converted to scientific notation to fit) 29 ! eg. F to S (0.003999, 3, 6) -> " 0.004" (fits exactly) 30 ! 31 %string(255) %function imp77 F to S( %longreal f, %integer sf, places) 32 %string(255) s,sx 33 %string(15) science 34 %integer dc,carry 35 %integer sign,exponent, digit, point 36 37 %if (sf > 14) %then sf = 14 38 39 %begin 40 %integer i 41 %integerarray digits(1:sf+1) 42 43 sign = 0 44 45 %for i = 1,1,sf+1 %cycle 46 digits(i) = 0 47 %repeat 48 49 %if (f < 0) %then sign = 1 %and f = -f 50 51 ! clear the floating point string 52 length(s) = 0 53 54 %if (f = 0) %start 55 ! convert to positive zero 56 sign = 0 57 dc = 2 58 sf = 2 59 exponent = 0 60 point = 1 61 %finish %else %start 62 ! prepare the exponent, point values for (f # 0) 63 ! evaluate the exponent value 64 exponent = 0 65 %while f < 1 %cycle 66 f = f * 10 67 exponent = exponent - 1 68 %repeat 69 70 %while f >= 10 %cycle 71 f = f / 10 72 exponent = exponent + 1 73 %repeat 74 75 ! locate the decimal point 76 point = 1 77 ! zero the digit count 78 dc = 0 79 80 ! Loop to get the significant figure digits with an extra digit 81 ! so we can use it to round the the required sig figs 82 ! Rounding as we go through this loop can "oversize" the digit. 83 ! The next stage does the rounding to the correct sig fig. 84 %for i = 1,1,sf + 1 %cycle 85 digit = int pt(f) 86 %if (digit > 9) %then digit = 9 87 dc = dc + 1 88 digits(dc) = digit 89 f = (f - digit)*10 90 %repeat 91 92 ! do the rounding to the sf significant figures 93 %if (digits(dc) > 4) %start 94 ! we need to possibly round up the digits sequence 95 carry = 1 96 %for i = dc - 1,-1,1 %cycle 97 digits(i) = digits(i) + carry 98 %if (digits(i) > 9) %start 99 carry = 1 100 digits(i) = 0 101 %finish %else %start 102 carry = 0 103 %finish 104 %repeat 105 %finish 106 ! ignore the rounding digit 107 dc = dc - 1 108 109 ! Now eliminate any trailing zeros 110 ! We assume that rounding has created 111 ! a sequence of trailing zeros 112 %while (digits(dc) = 0) %and (dc > 1) %cycle 113 dc = dc - 1 114 %repeat 115 sf = dc 116 %finish 117 118 length(s) = 0 119 point = 1 120 %for i = 1,1,sf %cycle 121 s = s.tostring(digits(i) + '0') 122 %if (point = i) %then s = s."." 123 %repeat 124 %if (sf = point) %then s = s."0" 125 %if (exponent < 0) %then s=s."@-".itos(-exponent,0) 126 %if (exponent > 0) %then s=s."@+".itos(exponent,0) 127 science = s 128 129 ! So, now for the other floating point layouts 130 ! we should see which version will fit into the places allowed 131 ! 1) 0.00000nnnn (point <= 0) 132 ! OR 133 ! 2) nnnn.0 (point = sf) 134 ! OR 135 ! 3) nnnn00000.0 (point > sf) 136 ! 137 length(s) = 0 138 point = exponent + 1 139 ! First form the sig fig digit string 140 ! possibly including a decimal point 141 %for i = 1,1,sf %cycle 142 s = s.tostring(digits(i) + '0') 143 %if (point = i) %then s = s."." 144 %repeat 145 146 ! Checking for format (1) 147 ! 1) 0.00000nnnn (point <= 0) 148 %if (point <= 0) %start 149 %for i=1,1,-point %cycle 150 s = "0".s 151 %repeat 152 s = "0.".s 153 %finish 154 155 ! Checking for format (2) 156 ! 2) nnnn.0 (point = sf) 157 %if (point = sf) %start 158 s = s."0" 159 %finish 160 161 ! Checking for format (3) 162 ! 3) nnnn00000.0 (point > sf) 163 %if (point > sf) %start 164 %for i = 1,1,(point - sf) %cycle 165 s = s."0" 166 %repeat 167 s = s.".0" 168 %finish 169 170 ! Check to see which fits scientific v decimal notation 171 ! Preference is for the decimal notation 172 %if (length(s) > places) %start 173 s = science 174 %finish 175 176 %if (sign # 0) %start 177 s = "-".s 178 %finish %else %start 179 s = " ".s 180 %finish 181 182 %if (length(s) < places) %start 183 %while (length(s) < places) %cycle 184 s = s." " 185 %repeat 186 %finish 187 %end 188 189 %result = s 190 %end ?SX unused 191 {----------------------------------------------------------------------------} 192 {----------------------------------------------------------------------------} 193 %routine imp77 print(%longreal f, %integer sf,places) 194 printstring( imp77 F to S( f, sf, places ) ) 195 %end 196 {----------------------------------------------------------------------------} 197 {----------------------------------------------------------------------------} 198 ! Print a floating point number out, along the lines of 199 ! +/-nnn.nnn@+/-nn, to occupy Places character spaces. 200 ! Note - there's a bug in this code such that it does not 201 ! round the number properly. EG 3.999999999 to 4 places 202 ! should be 4.00 but we print 3.99 203 204 %routine imp77 printfl(%longreal x, %integer places) 205 %integer exponent, digit, point, printexpo 206 207 %if x = 0 %start 208 printsymbol('0') 209 printsymbol('.') 210 printsymbol('0') 211 %while places > 3 %cycle 212 printsymbol('0') 213 places = places - 1 214 %repeat 215 %return 216 %finish 217 218 %if x < 0 %then printsymbol('-') %and x = -x %and places = places - 1 219 220 %if places < 3 %then places = 3 221 222 exponent = 0 223 printexpo = 0 224 225 %while x < 1 %cycle 226 x = x * 10 227 exponent = exponent - 1 228 %repeat 229 230 %while x >= 10 %cycle 231 x = x / 10 232 exponent = exponent + 1 233 %repeat 234 235 ! Now X is between 1.0 and 9.99 and exponent is set accordingly 236 ! If the exponent is "large" we will use scientific notation 237 point = places - 2; ! for useful digits after the "0." 238 %if exponent >= places %or exponent < -point %start 239 printexpo = exponent 240 exponent = 0 241 places = places - 2 242 %finish 243 244 ! Now the exponent is small-ish 245 %if exponent < 0 %start; ! 0.nnnn 246 printsymbol('0') 247 printsymbol('.') 248 places = places - 2 249 250 %while exponent < -1 %cycle 251 printsymbol('0') 252 exponent = exponent + 1 253 places = places - 1 254 %repeat 255 256 point = -1; ! because we've already passed that 257 %else; ! nnn.nnn 258 point = exponent 259 %finish 260 261 %while places > 0 %cycle 262 digit = int pt(x) 263 ! Rounding as we go through this loop can "oversize" the digit. This 264 ! of course tells us that we should have printed (eg) 40000 but we 265 ! are now stuck with printing 39999 266 %if digit > 9 %then digit = 9 267 printsymbol(digit + '0') 268 x = (x - digit)*10 269 %if point = 0 %then printsymbol('.') %and places = places - 1 270 point = point - 1 271 places = places - 1 272 %repeat 273 274 %if printexpo # 0 %start 275 printsymbol('@') 276 !! write68k(printexpo, 1) 277 %finish 278 %end 279 280 %endofprogram ?IMP77PRINTFL unused ?IMP77PRINT unused 166 Statements compiled