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Task/Roman-numerals-Decode/TechBASIC/roman-numerals-decode.basic

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+Main:
+!------------------------------------------------
+! CALLS THE romToDec FUNCTION WITH THE ROMAN
+! NUMERALS AND RETURNS ITS DECIMAL EQUIVELENT.
+!
+
+   PRINT "MCMXC   = "; romToDec("MCMXC")   !1990
+   PRINT "MMVIII  = "; romToDec("MMVIII")  !2008
+   PRINT "MDCLXVI = "; romToDec("MDCLXVI") !1666
+   PRINT:PRINT
+   PRINT "Here are other solutions not from the TASK:"
+   PRINT "MCMXCIX = "; romToDec("MCMXCIX") !1999
+   PRINT "XXV     = "; romToDec("XXV")     !25
+   PRINT "CMLIV   = "; romToDec("CMLIV")   !954
+   PRINT "MMXI    = "; romToDec("MMXI")    !2011
+   PRINT:PRINT
+   PRINT "Without error checking, this also is 2011, but is wrong"
+   PRINT "MMIIIX  = "; romToDec("MMIIIX")  !INVAID, 2011
+
+STOP
+
+
+FUNCTION romToDec(roman AS STRING) AS INTEGER
+!------------------------------------------------------
+! FUNCTION THAT CONVERTS ANY ROMAN NUMERAL TO A DECIMAL
+!
+    prenum=0!num=0
+    ln=LEN(roman)
+    FOR i=ln TO 1 STEP -1
+        x$=MID(roman,i,1)
+        n=1000
+        SELECT CASE x$
+               CASE "M":n=n/1
+               CASE "D":n=n/2
+               CASE "C":n=n/10
+               CASE "L":n=n/20
+               CASE "X":n=n/100
+               CASE "V":n=n/200
+               CASE "I":n=n/n
+               CASE ELSE:n=0
+        END SELECT
+        IF n < preNum THEN num=num-n ELSE num=num+n
+        preNum=n
+   next i
+
+   romToDec=num
+
+END FUNCTION