# Lexical analysis
In the lexical analysis step, the expl3 analysis tool converts the expl3 parts of the input files into a list of `\TeX`{=tex} tokens.
## “Do not use” argument specifiers {.w label=w200}
Some control sequence tokens correspond to functions with `D` (do not use) argument specifiers.
/w200.tex
The above example has been taken from @latexteam2024interfaces [Chapter 24].
## Unknown argument specifiers {.e label=e201}
Some control sequence tokens correspond to functions with unknown argument specifiers. [@latexteam2024interfaces, Section 1.1]
/e201.tex
## Deprecated control sequences {.w label=w202}
Some control sequence tokens correspond to deprecated expl3 control sequences from `l3obsolete.txt` [@josephwright2024obsolete].
/w202.tex
## Removed control sequences {.e label=e203 removed=2025-02-14}
Some control sequence tokens correspond to removed expl3 control sequences from `l3obsolete.txt` [@josephwright2024obsolete].
/e203.tex
## Missing stylistic whitespaces {.s label=s204}
Some control sequences and curly braces are not surrounded by whitespaces [@latexteam2024programming, Section 6] [@latexteam2024style, Section 3].
/s204.tex
## Malformed function name {.s label=s205}
Some function have names that are not in the format `\texttt{\textbackslash\meta{module}\_\meta{description}:\meta{arg-spec}}`{=tex} [@latexteam2024programming, Section 3.2].
## Malformed variable or constant name {.s label=s206}
Some expl3 variables and constants have names that are not in the format `\texttt{\textbackslash\meta{scope}\_\meta{module}\_\meta{description}\_\meta{type}}`{=tex} [@latexteam2024programming, Section 3.2], where the `\meta{module}`{=tex} part is optional.
/s206-01.tex
/s206-02.tex
An exception is made for scratch variables [@latexteam2024interfaces, Section 1.1.1]:
/s206-03.tex
## Malformed quark or scan mark name {.s label=s207}
Some expl3 quarks and scan marks have names that do not start with `\q_` and `\s_`, respectively [@latexteam2024programming, Chapter 19].
