• Corpus ID: 5413577

A History of the SNOBOL Programming Languages

@inproceedings{ShapiroAHO,
  title={A History of the SNOBOL Programming Languages},
  author={Michael D. Shapiro}
}

• Michael D. Shapiro

The SNOBOL programming languages introduced or popularized most of the concepts of character string processing. The original SNOBOL had just one data type: a string of characters. It could appear in a program as a literal delimited by quotation marks, or as a value assigned to a variable: PET " "MY CALICO CAT" Concatenation, a basic string operation, forms a new string from two or more strings placed end to end: MYPET • "HERE IS " PET "." concatenates the string "HERE IS ", the value in the variable PET, and the string ". " to form the string "HERE IS MY CALICO CAT. " and assigns it to the variable MYPET. Another fundamental operation is the pattern match. It examines the contents of a string as specified by a sequence of pattern elements. The elements may be strings (variables or literals) or special patterns delimited by asterisks. The original special patterns matched a fixed length string, an arbitrary string (between two other elements), or a string "balanced with respect to parentheses" (for algebraic expression process ing). A program is a sequence of statements. Each statement may contain up to three parts; all are optional. The first part of a statement is a label, allowing branching to that statement. The second part is the rule, specifying the action to be taken. The final part, the go-to, controls flow to the next program statement. The sample SNOBOL program shown below demonstrates several of the language features. It reads lines of text, changes the vowels to asterisks, and prints the result.