Reading Floating-point Numbers

A floating-point argument has a format specifier in one of the following forms:

f[*|@2|@3][width][,[arraySize]]f

e[*|@2|@3][width][,[arraySize]]e

E[*|@2|@3][width][,[arraySize]]E

g[*|@2|@3][width][,[arraySize]]g

G[*|@2|@3][width][,[arraySize]]G

Note that they are identical except for the format type.

Modifier	Interpretation
Default Functionality	The argument is interpreted as a floating point number.
flags * @2, @3	Controls parsing, as follows: '*' indicates that the data is to be parsed and skipped - there is no corresponding output argument in the Scanf call. '@2' formats the value in IEEE 488.2 NR2 format. '@3' formats the value in IEEE 488.2 NR3 format.
width	For types e, E, and f, the actual number of digits after the decimal point. For types g and G, the actual number of significant digits. A hash character (#) may be present in lieu of an integer width modifier, in which case an extra Int32 argument supplies the value.
,[arraySize]	Format an array of integers converted to strings. If arraySize is specified, it is the maximum number of elements to include in the formatted array. A hash character (#) may be present in lieu of an integer arraySize modifier, in which case an extra Int32 argument supplies the value.

Floating Point Parsing Code Snippets

Remember that Scanf is reading bytes from the formatted read buffer, parsing them according to the format specifiers, and placing the results in an output variable. The comment preceding each line shows the data being parsed by the snippet, and the resulting value that is returned in the corresponding output argument, like this: // "<data to parse>", "<value>". The <value> may optionally be followed by a comment in parentheses.

For Scanf arrays, output array sizes are calculated from the size of the data. For ScanfArray, which is unsafe, the calling program must allocate an array that is guaranteed to be large enough to hold the parsed array.

Assume that the io variable is a valid reference to IMessageBasedFormattedIO. Assume that result1 is an out argument declared as a .NET Single or Double. Either type is capable of holding any of the numbers used in these snippets.

Flags	Copy Code
// "25.135, 3.5135e+01, -4.5135E+01 \n ", 25.135, 35.135, -45.135 io.Scanf("%f, %e, ET", out result1); // "25.135, 3.5135e+01, -4.5135E+01 \n ", 35.135 io.Scanf("%f, %e, ET", out result1);

Flags

Copy Code

// "25.135, 3.5135e+01, -4.5135E+01 \n ", 25.135, 35.135, -45.135

io.Scanf("%f, %e, E*T", out result1);

// "25.135, 3.5135e+01, -4.5135E+01 \n ", 35.135

io.Scanf("%*f, %e, *E*T", out result1);

Width Modifiers	Copy Code
// "25.135\n", 25.1 io.Scanf("%4f%T", out result1); // "12345\n", 1234.0 io.Scanf("#fT", new Int64[] { 4 }, out result1); // "2.5135E+011", 25.135 (the trailing '1' is not parsed.) io.Scanf("10ET", out result1); // "2.5135E+011", 251350000000.00 io.Scanf("#ET", new Int64[] { 20 }, out result1);

Width Modifiers

Copy Code

// "25.135\n", 25.1

io.Scanf("%4f%*T", out result1);

// "12345\n", 1234.0

io.Scanf("#f*T", new Int64[] { 4 }, out result1);

// "2.5135E+011", 25.135 (the trailing '1' is not parsed.)

io.Scanf("10E*T", out result1);

// "2.5135E+011", 251350000000.00

io.Scanf("#E*T", new Int64[] { 20 }, out result1);

IEEE 488.2 Format Modifiers	Copy Code
// "25.135\n", 25.135 io.Scanf("@2fT", out result1); // "2.5135E+001\n", 25.135 io.Scanf("@3e**T", out result1);

IEEE 488.2 Format Modifiers

Copy Code

// "25.135\n", 25.135

io.Scanf("@2f*T", out result1);

// "2.5135E+001\n", 25.135

io.Scanf("@3e*T", out result1);

ScanfArray	Copy Code
// "1.23, 2.34, 3.45, 4.56\n", { 1.23, 2.34, 3.45, 4.56 } - Memory must be allocated // by the calling program. Double[10] out1; io.ScanfArray("%,f%*T", out1);

ScanfArray

Copy Code

// "1.23, 2.34, 3.45, 4.56\n", { 1.23, 2.34, 3.45, 4.56 } - Memory must be allocated

// by the calling program.

Double[10] out1;

io.ScanfArray("%,f%*T", out1);