S-expression
S-expression is an actively used meta language created in 1960. In computing, s-expressions, sexprs or sexps (for "symbolic expression") are a notation for nested list (tree-structured) data, invented for and popularized by the programming language Lisp, which uses them for source code as well as data. In the usual parenthesized syntax of Lisp, an s-expression is classically defined as an atom, or an expression of the form (x . y) where x and y are s-expressions. Read more on Wikipedia...
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- S-expression ranks in the top 25% of languages
- the S-expression wikipedia page
- S-expression first appeared in 1960
- See also: lisp, scheme, c, common-lisp, xml, python, islisp, rfc, i-expressions, bayer-expressions
- Have a question about S-expression not answered here? Email me and let me know how I can help.
Example code from Wikipedia:
def parse_sexp(string):
"""
>>> parse_sexp("(+ 5 (+ 3 5))")
[['+', '5', ['+', '3', '5']]]
"""
sexp = [[]]
word = ''
in_str = False
for char in string:
if char is '(' and not in_str:
sexp.append([])
elif char is ')' and not in_str:
if word:
sexp[-1].append(word)
word = ''
temp = sexp.pop()
sexp[-1].append(temp)
elif char in (' ', '\n', '\t') and not in_str:
if word:
sexp[-1].append(word)
word = ''
elif char is '\"':
in_str = not in_str
else:
word += char
return sexp[0]
Last updated May 25th, 2020