i1 : (optP constParser "abc" : charAnalyzer) "" o1 = nil o1 : Symbol
i2 : (optP constParser "abc" : charAnalyzer) "abc" o2 = abc
The object nil is a symbol.
The source of this document is in /build/reproducible-path/macaulay2-1.26.06+ds/M2/Macaulay2/packages/Parsing.m2:300:0.