Character¶

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description¶

Character

is a type specification in Read and ReadList that reads a single character, returned as a one-character string.

Examples (2)¶

Every input below was run against the current Mathilda build and its output recorded.

Applications (2)¶

Reads one character as a string

In[1]:= s = OpenWrite["/tmp/mathilda_char.txt"]; WriteString[s, "Hi"]; Close[s]; Read["/tmp/mathilda_char.txt", Character]
Out[1]= "H"

One of the eight read types

In[2]:= MemberQ[{Byte, Character, Expression, Number, Real, Record, String, Word}, Character]
Out[2]= True

Implementation notes¶

Definition. Character is a type specification used by Read and ReadList. It has no builtin and no value — it is an inert token that tells the reader to consume exactly one character from the stream and return it as a one-character string.

Representation. A bare EXPR_SYMBOL (interned SYM_Character). read.c's type_from_symbol maps it to the internal RT_CHARACTER reader, one of the eight read types (Byte, Character, Expression, Number, Real, Record, String, Word). It may appear on its own or nested inside a type-structure argument ({Character, Character}, Hold[...], any head), which the reader fills depth-first.

Usage & limits. Meaningful only as a Read/ReadList type argument; evaluated on its own it simply returns itself. Past end of file the reader returns EndOfFile. Contrast Byte, which returns the raw integer code 0-255 rather than a string.

Attributes: none registered.

References¶

Source: src/io/read.c
Specification index: Mathilda_spec.md

Notes & additional examples¶

Notes¶

Character is a type specification for Read and ReadList: it consumes exactly one character from the stream and returns it as a one-character string. It has no value of its own, so on its own it just evaluates to itself.

It may stand alone or nest inside a type structure ({Character, Character}, Hold[...], any head), which the reader fills depth-first. Contrast Byte, which returns the raw integer code 0-255 instead of a string. Past end of file the reader returns EndOfFile.