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Floating Point Basics ===================== Emacs version 19 supports floating point numbers, if compiled with the macro `LISP_FLOAT_TYPE' defined. The precise range of floating point numbers is machine-specific; it is the same as the range of the C data type `double' on the machine in question. The printed representation for floating point numbers requires either a decimal point (with at least one digit following), an exponent, or both. For example, `1500.0', `15e2', `15.0e2', `1.5e3', and `.15e4' are five ways of writing a floating point number whose value is 1500. They are all equivalent. You can also use a minus sign to write negative floating point numbers, as in `-1.0'. You can use `logb' to extract the binary exponent of a floating point number (or estimate the logarithm of an integer): - Function: logb NUMBER This function returns the binary exponent of NUMBER. More precisely, the value is the logarithm of NUMBER base 2, rounded down to an integer.