The following code, from the wiki, results in a compilation error:

\starttext
> \ctxlua{context(string.format("\%.2f", math.pi))}
> \stoptext


The error is:

[\directlua]:1: invalid escape sequence near '\%'
> 1     \starttext
> 2
> 3 >>  \ctxlua{context(string.format("\%.2f", math.pi))}
> 4
> 5     \stoptext


I ended using \letterpercent command but it is not very convenient.

Any help is welcome,

Antoine C.

Full log:

mtx-context     | warning: synctex is enabled
> mtx-context     | run 1: luatex
> --fmt="/usr/local/texlive/2015/texmf-var/luatex-cache/context/a86c089b384a3076dc514ba966a1fac9/formats/luatex/cont-en"
> --jobname="luapercent"
> --lua="/usr/local/texlive/2015/texmf-var/luatex-cache/context/a86c089b384a3076dc514ba966a1fac9/formats/luatex/cont-en.lui"
> --no-parse-first-line --synctex=1 --c:autogenerate --c:currentrun=1
> --c:directives="system.synctex=1"
> --c:fulljobname="/Users/acailliau/Desktop/luapercent.tex"
> --c:input="/Users/acailliau/Desktop/luapercent.tex" --c:kindofrun=1
> --c:maxnofruns=9 --c:synctex="1" "cont-yes.mkiv"
> This is LuaTeX, Version beta-0.80.0 (TeX Live 2015) (rev 5238)
>  \write18 enabled.
> system          > synctex functionality is enabled (1)!
> open source     > 1 > 1 >
> /usr/local/texlive/2015/texmf-dist/tex/context/base/cont-yes.mkiv
> ConTeXt  ver: 2015.05.18 12:26 MKIV current  fmt: 2016.4.25  int:
> english/english
> system          > 'cont-new.mkiv' loaded
> open source     > 2 > 2 >
> /usr/local/texlive/2015/texmf-dist/tex/context/base/cont-new.mkiv
> close source    > 2 > 2 >
> /usr/local/texlive/2015/texmf-dist/tex/context/base/cont-new.mkiv
> system          > files > jobname 'luapercent', input
> '/Users/acailliau/Desktop/luapercent', result 'luapercent'
> fonts           > latin modern fonts are not preloaded
> languages       > language 'en' is active
> open source     > 2 > 3 > /Users/acailliau/Desktop/luapercent.tex
> fonts           > preloading latin modern fonts (second stage)
> fonts           > 'fallback modern-designsize rm 12pt' is loaded
> lua error       > error on line 3 in file
> /Users/acailliau/Desktop/luapercent.tex:
> [\directlua]:1: invalid escape sequence near '\%'
> 1     \starttext
> 2
> 3 >>  \ctxlua{context(string.format("\%.2f", math.pi))}
> 4
> 5     \stoptext
>
> ? Type  to proceed, S to scroll future error messages,
> R to run without stopping, Q to run quietly,
> I to insert something,
> 1 or ... or 9 to ignore the next 1 to 9 tokens of input,
> H for help, X to quit.
> ? close source    > 2 > 3 > /Users/acailliau/Desktop/luapercent.tex
> close source    > 1 > 3 >
> /usr/local/texlive/2015/texmf-dist/tex/context/base/cont-yes.mkiv
> mkiv lua stats  > used config file:
> selfautoparent:/texmfcnf.lua;selfautoparent:/texmf-dist/web2c/texmfcnf.lua
> mkiv lua stats  > used cache path:
> /usr/local/texlive/2015/texmf-var/luatex-cache/context/a86c089b384a3076dc514ba966a1fac9
> mkiv lua stats  > synctex tracing: synctex has been enabled (extra log
> file generated)
> mkiv lua stats  > resource resolver: loadtime 0.117 seconds, 0 scans with
> scantime 0.000 seconds, 0 shared scans, 8 found files, scanned paths:
> mkiv lua stats  > stored bytecode data: 371 modules (0.309 sec), 78 tables
> (0.008 sec), 449 chunks (0.316 sec)
> mkiv lua stats  > traced context: maxstack: 1132, freed: 0, unreachable:
> 1132
> mkiv lua stats  > running in nuts mode: yes
> mkiv lua stats  > cleaned up reserved nodes: 41 nodes, 439 lists of 438
> mkiv lua stats  > node memory usage: 2 glue, 2 penalty, 6 attribute, 26
> glue_spec, 2 attribute_list, 2 temp
> mkiv lua stats  > node list callback tasks: 6 unique task lists, 2
> instances (re)created, 3 calls
> mkiv lua stats  > used backend: pdf (backend for directly generating pdf
> output)
> mkiv lua stats  > loaded patterns: en::2, load time: 0.000
> mkiv lua stats  > jobdata time: 0.001 seconds saving, 0.000 seconds loading
> mkiv lua stats  > callbacks: 60 direct, 243 indirect, 303 total
> mkiv lua stats  > result saved in file: luapercent.pdf, compresslevel 3,
> objectcompresslevel 3
> mkiv lua stats  > loaded fonts: 2 files: latinmodern-math.otf,
> lmroman12-regular.otf
> mkiv lua stats  > fonts load time: 0.180 seconds
> mkiv lua stats  > used platform: osx-64, type: unix, binary subtree: bin
> mkiv lua stats  > luatex banner: this is luatex, version beta-0.80.0 (tex
> live 2015) (rev 5238)
> mkiv lua stats  > control sequences: 43101 of 65536 + 100000
> mkiv lua stats  > lua properties: engine: lua, used memory: 67 MB (ctx: 66
> MB), hash type: lua, hash chars: min(64,40), symbol mask: utf (τεχ)
> mkiv lua stats  > runtime: 0.540 seconds
> mtx-context     | fatal error: return code: 1