Number¶
Status: Stable
documented, exercised by the test suite and/or worked examples, with no known limitations recorded.
Description¶
Number
is a type specification in Read and ReadList that reads a number, returned as an integer when the token has no decimal point or exponent and as an approximate number otherwise.
Examples (3)¶
Every input below was run against the current Mathilda build and its output recorded.
Applications (3)¶
The type token stays inert — it has no value of its own
It is a plain Symbol
And carries no attributes
Implementation notes¶
Definition. Number is a type specification used in Read and ReadList: it reads a number, returned as an integer when the token has no decimal point or exponent and as an approximate number otherwise.
It is an inert symbol — no builtin, no value, no attributes — declared with its
docstring in info.c and recognised by the reader.
Representation. A bare EXPR_SYMBOL. The read-type scanner in src/io/read.c
maps it to an internal read-type tag (if (n == SYM_Number) *out = RT_...), after
which the matching reader pulls the value from the stream. As a plain symbol
its Head is Symbol and it carries no attributes.
Usage & limits. Meaningful only as the type argument of Read/ReadList over a
file or an open stream; standing alone it is just a symbol. an integer-looking token reads back as an Integer and a decimal or exponent token as a Real.
Attributes: none registered.
References¶
- Source:
src/io/read.c - Specification index:
Mathilda_spec.md
Notes & additional examples¶
Notes¶
Number is a Read/ReadList type specification: it reads a number, returned as an integer when the token has no decimal point or exponent and as an approximate number otherwise. A read that uses it, such as
ReadList["data.txt", Number], needs a file (or open stream) on disk, so the runnable examples above show
only that the token itself is an inert symbol — an integer-looking token reads back as an Integer and a decimal or exponent token as a Real.