read-number

Reading numbers from an input stream without using the Lisp reader.

Functions

read-integer (&optional input-stream eof-error-p eof-value recursivep &key unsigned-number plus-sign minus-sign group-separator radix)

Read an integer from an input stream.

read-float (&optional input-stream eof-error-p eof-value recursivep &key unsigned-number plus-sign minus-sign group-separator decimal-point exponent-marker float-format significand-radix exponent-radix exponent-base)

Read a floating-point number from an input stream.

Features

• Optional arguments input-stream, eof-error-p, eof-value, and recursivep behave similar to read.

• Keyword argument unsigned-number controls the sign conventions; plus or minus sign, minus sign only (no explicit plus sign), or unsigned.

• Keyword arguments plus-sign, minus-sign, group-separator, decimal-point, and exponent-marker denote character sets.

• Keyword arguments significand-radix, exponent-radix, and exponent-base provide support for reading, for example, C99 hexadecimal floating-point literals.

• Leading and trailing whitespace is not ignored.

• Compatible with with-input-from-string.

Commentary

The read-integer and read-float functions are designed to read external number representations. The read-number function (to be defined) is reserved for reading any Lisp number representation.

The functions provided by read-number are different to parse-number and parse-float because they read characters sequentially from a stream instead of parsing a string directly.