Scientific notation: Difference between revisions
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Xpos% = {{Cl|INSTR}}(value$, "D") + {{Cl|INSTR}}(value$, "E") 'only D or E can be present | Xpos% = {{Cl|INSTR}}(value$, "D") + {{Cl|INSTR}}(value$, "E") 'only D or E can be present | ||
{{Cl|IF}} Xpos% {{Cl|THEN}} | {{Cl|IF}} Xpos% {{Cl|THEN}} | ||
expo% = {{Cl|VAL}}({{Cl|MID$}}(value$, Xpos% + 1)) | expo% = {{Cl|VAL}}({{Cl|MID$ (function)|MID$}}(value$, Xpos% + 1)) | ||
{{Cl|IF}} {{Cl|VAL}}(value$) < 0 {{Cl|THEN}} | {{Cl|IF}} {{Cl|VAL}}(value$) < 0 {{Cl|THEN}} | ||
sign$ = "-": valu$ = {{Cl|MID$}}(value$, 2, Xpos% - 2) | sign$ = "-": valu$ = {{Cl|MID$ (function)|MID$}}(value$, 2, Xpos% - 2) | ||
{{Cl|ELSE}} valu$ = {{Cl|MID$}}(value$, 1, Xpos% - 1) | {{Cl|ELSE}} valu$ = {{Cl|MID$ (function)|MID$}}(value$, 1, Xpos% - 1) | ||
{{Cl|END IF}} | {{Cl|END IF}} | ||
dot% = {{Cl|INSTR}}(valu$, "."): L% = {{Cl|LEN}}(valu$) | dot% = {{Cl|INSTR}}(valu$, "."): L% = {{Cl|LEN}}(valu$) | ||
| Line 45: | Line 45: | ||
{{Cl|IF}} expo% < 0 {{Cl|THEN}} min$ = {{Cl|STRING$}}({{Cl|ABS}}(expo%) - (dot% - 1), "0"): DP$ = "." | {{Cl|IF}} expo% < 0 {{Cl|THEN}} min$ = {{Cl|STRING$}}({{Cl|ABS}}(expo%) - (dot% - 1), "0"): DP$ = "." | ||
{{Cl|FOR...NEXT|FOR}} n = 1 {{Cl|TO}} L% | {{Cl|FOR...NEXT|FOR}} n = 1 {{Cl|TO}} L% | ||
{{Cl|IF}} {{Cl|MID$}}(valu$, n, 1) <> "." {{Cl|THEN}} num$ = num$ + {{Cl|MID$}}(valu$, n, 1) | {{Cl|IF}} {{Cl|MID$ (function)|MID$}}(valu$, n, 1) <> "." {{Cl|THEN}} num$ = num$ + {{Cl|MID$ (function)|MID$}}(valu$, n, 1) | ||
{{Cl|NEXT}} | {{Cl|NEXT}} | ||
{{Cl|ELSE}} StrNum$ = value$: {{Cl|EXIT FUNCTION}} | {{Cl|ELSE}} StrNum$ = value$: {{Cl|EXIT FUNCTION}} | ||
| Line 52: | Line 52: | ||
{{Cl|END FUNCTION}} | {{Cl|END FUNCTION}} | ||
{{CodeEnd}} | {{CodeEnd}} | ||
{{ | {{Small|Code by Ted Weissgerber}} | ||
{{OutputStart}} | {{OutputStart}} | ||
-2.34D-15 | -2.34D-15 | ||
Latest revision as of 00:45, 26 February 2023
Scientific notation or exponential notation is used to express very large or small numerical values by SINGLE or DOUBLE accuracy.
Usage: -9.7587E+04 or 4.6545D-9
- E denotes SINGLE precision accuracy and D denotes DOUBLE precision accuracy in QBasic. D and E are considered numbers!
- To translate the notation, multiply the number preceding the letter by the value of 10 raised to the power following the letter.
- PRINT USING can display the normal numerical values. You will have to use less digits than the real value.
- Note: Naturally numerically calculating the value in QBasic would return the same value!
- INPUT WILL accept the letter E with SINGLE or DOUBLE variables while D can only be used with DOUBLE variables.
Sample 1: +2.184D+3 means to multiply 2.184 by 1,000 (1,000 is 10 raised to the third power, or 10 ^ 3 ).
- To multiply by 10 raised to a positive power, just move the decimal point to the right by 3.
- The result is 2184 in DOUBLE accuracy.
Sample 2: -5.412D-2 is negative 5.412 times .01 (10 raised to the -2 power or 10 ^ -2 ).
- To multiply a number by 10 raised to a negative power, just move the decimal point to the left by 2.
- The result is -.05412 in DOUBLE accuracy.
Sample 3: 3.07E+12 is a positive 3.07 times 1,000,000,000,000 (10 raised to the 12 power or 10 ^ 12).
- To multiply a number by 10 raised to a positive power, just move the decimal point to the right by 12.
- The result is 3,070,000,000,000 in SINGLE accuracy.
Example: A string function that displays extremely small or large exponential decimal values.
num# = -2.34D-15 PRINT num# PRINT StrNum$(num#) END FUNCTION StrNum$ (n#) value$ = UCASE$(LTRIM$(STR$(n#))) Xpos% = INSTR(value$, "D") + INSTR(value$, "E") 'only D or E can be present IF Xpos% THEN expo% = VAL(MID$(value$, Xpos% + 1)) IF VAL(value$) < 0 THEN sign$ = "-": valu$ = MID$(value$, 2, Xpos% - 2) ELSE valu$ = MID$(value$, 1, Xpos% - 1) END IF dot% = INSTR(valu$, "."): L% = LEN(valu$) IF expo% > 0 THEN add$ = STRING$(expo% - (L% - dot%), "0") IF expo% < 0 THEN min$ = STRING$(ABS(expo%) - (dot% - 1), "0"): DP$ = "." FOR n = 1 TO L% IF MID$(valu$, n, 1) <> "." THEN num$ = num$ + MID$(valu$, n, 1) NEXT ELSE StrNum$ = value$: EXIT FUNCTION END IF StrNum$ = sign$ + DP$ + min$ + num$ + add$ END FUNCTION |
-2.34D-15 -.00000000000000234 |
See also