Less-than sign

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The less-than sign is a mathematical symbol that denotes an inequality between two values. The widely adopted form of two equal-length strokes connecting in an acute angle at the left, <, has been found in documents dated as far back as the 1560s. In mathematical writing, the less-than sign is typically placed between two values being compared and signifies that the first number is less than the second number. Examples of typical usage include 1⁄2 < 1 and −2 < 0.

Since the development of computer programming languages, the less-than sign and the greater-than sign have been repurposed for a range of uses and operations.

Computing[]

The less-than sign, <, is an original ASCII character (hex 3C, decimal 60).

The less-than sign may be used for an approximation of the opening angle bracket, ⟨. ASCII does not have angle brackets but are standard in Unicode (U+2329 〈 LEFT-POINTING ANGLE BRACKET (HTML 〈)). The latter is expected in formal texts.

Programming language[]

In BASIC, Lisp-family languages, and C-family languages (including Java and C++), comparison operator < means "less than".

In Coldfusion, operator .lt. means "less than".

In Fortran, operator .LT. means "less than"; later versions allow <.

In Bourne shell, operator -lt means "less than".

Double less-than sign[]

The double less-than sign, <<, may be used for an approximation of the much-less-than sign (≪) or of the opening guillemet («). ASCII does not encode either of these signs, though they are both included in Unicode.

In Bash, Perl, and Ruby, operator <<EOF (where "EOF" is an arbitrary string, but commonly "EOF" denoting "end of file") is used to denote the beginning of a here document.

In C and C++, operator << represents a binary left shift.

In the C++ Standard Library, operator <<, when applied on an output stream, acts as insertion operator and performs an output operation on the stream.

In Ruby, operator << acts as append operator when used between an array and the value to be appended.

In XPath the << operator returns true if the left operand precedes the right operand in document order; otherwise it returns false.^[1]

Triple less-than sign[]

In PHP, operator <<<OUTPUT is used to denote the beginning of a heredoc statement (where OUTPUT is an arbitrary named variable.)

In Bash, <<<word is used as a "here string", where word is expanded and supplied to the command on its standard input, similar to a heredoc.

Less-than sign plus equals sign[]

The less-than sign plus the equals sign, <=, may be used for an approximation of the less-than-or-equal-to sign, ≤. ASCII does not have a less-than-or-equal-to sign, but Unicode defines it at code point U+2264.

In BASIC, Lisp-family languages, and C-family languages (including Java and C++), operator <= means "less than or equal to". In Sinclair BASIC it is encoded as a single-byte code point token.

In Prolog, =< means "less than or equal to" (as distinct from the arrow <=).

In Fortran, operator .LE. means "less than or equal to".

In Bourne shell and Windows PowerShell, the operator -le means "less than or equal to".

Less-than sign plus Hyphen-minus[]

In the R programming language, the less-than sign is used in conjunction with a hyphen-minus to create an arrow (<-), this can be used as the left assignment operator.

Shell scripts[]

In Bourne shell (and many other shells), less-than sign is used to redirect input from a file. Less-than plus ampersand (<&) is used to redirect from a file descriptor.

Spaceship operator[]

Less-than sign is used in the spaceship operator.

HTML[]

In HTML (and SGML and XML), the less-than sign is used at the beginning of tags. The less-than sign may be included with <. The less-than-or-equal-to sign, ≤, may be included with ≤.

Mathematics[]

In an inequality, the less-than sign and greater-than sign always "point" to the smaller number. Put another way, the "jaws" (the wider section of the symbol) always direct to the larger number.

See also[]

• Inequality (mathematics)
• Greater-than sign
• Relational operator
• Much-less-than sign

References[]