Halstead

Unique Operators

halstead.unique_operators — n1.

Item	Value
Definition	Number of distinct operators.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	count
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Unique Operands

halstead.unique_operands — n2.

Item	Value
Definition	Number of distinct operands.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	count
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Total Operators

halstead.total_operators — N1.

Item	Value
Definition	Number of operator occurrences.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	count
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Total Operands

halstead.total_operands — N2.

Item	Value
Definition	Number of operand occurrences.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	count
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Vocabulary

halstead.vocabulary — n.

Item	Value
Definition	n = n1 + n2.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	count
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Program Length

halstead.length — N.

Item	Value
Definition	N = N1 + N2.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	count
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Volume

halstead.volume — V.

Item	Value
Definition	V = N * log2(n); not_applicable when n = 0.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	bits
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Difficulty

halstead.difficulty — D.

Item	Value
Definition	D = (n1 / 2) * (N2 / n2); not_applicable when n2 = 0.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	ratio
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Effort

halstead.effort — E.

Item	Value
Definition	E = D * V.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	count
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Estimated Program Time

halstead.time — T.

Item	Value
Definition	T = E / 18.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	seconds
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.

Estimated Bugs

halstead.bugs — B.

Item	Value
Definition	B = V / 3000.
Scope	function, file, project
Input	Tokens (kind and text)
Calculation	Operators: keyword and operator tokens and opening brackets ( [ {. Operands: identifier and literal tokens. Commas, semicolons, closing brackets and comments are not counted. Distinct = same token text.
Unit	count
Language Applicability	partially_language_dependent
Limitations	Keywords, including type keywords such as int, are operators. A string literal is one operand.
Reference	Halstead, M. H. (1977). Elements of Software Science. Elsevier.