[Rd] Unicode substitutions for Rd2txt \[d]eqn{}
Kurt Hornik
Kurt@Horn|k @end|ng |rom wu@@c@@t
Wed May 13 15:32:26 CEST 2026
>>>>> Ivan Krylov via R-devel writes:
I like your patch :-)
Perhaps do this conditionally on Rd2txt_options()$unicode_symbols set to
TRUE?
Best
-k
> Hello R-devel,
> The idea to use Unicode when rendering equations in plain text was
> mentioned a few times in the past, most recently by Sebastian Meyer in
> a Bugzilla comment. I would like to share the patch to use Unicode
> characters for approximately the same symbols that used to be
> substituted in the old HTML equation renderer.
> Why do it? Familiar Greek letters would be more consistent with HTML
> and PDF documentation.
> What are the downsides?
> - Some symbols don't look as good on a terminal as they do in a
> document when typeset with a mathematical font. Depending on the
> font used in the terminal, \pi → π may look very similar to n. (For
> example, the popular Terminus font uses exactly the same glyph for
> 'π', U+03C0 GREEK SMALL LETTER PI, and 'п', U+043F CYRILLIC SMALL
> LETTER PE.) \infty → '∞' and \dots → '…' are too small and narrow
> when rendered at the same width as normal monospace letters. '√',
> 'Σ'/'∑', and 'Π'/'∏' may look too unexpected compared to 'sqrt',
> 'sum', and 'prod'.
> - There may be accessibility implications. Would a screen reader
> struggle upon seeing a 'Π' instead of 'prod'? Hopefully the screen
> reader users can enjoy the more accessible HTML documentation now,
> and there is an option to disable the Unicode symbols.
> - The patch is only mildly tested by reading ?stats::TDist and
> ?pracma::expint and making sure that for (pkg in
> rownames(installed.packages())) for (Rd in tools::Rd_db(pkg))
> tools::Rd2txt(Rd) doesn't fail, with or without a UTF-8-capable
> locale.
> Thanks to Sebastian Meyer for the initial comments!
> Index: src/library/tools/R/Rd2HTML.R
> ===================================================================
> --- src/library/tools/R/Rd2HTML.R (revision 90047)
> +++ src/library/tools/R/Rd2HTML.R (working copy)
> @@ -109,14 +109,13 @@
> x <- fsub('"\\{"', '"{"', x)
> ## http://htmlhelp.com/reference/html40/entities/symbols.html
> if(inEqn) {
> - x <- psub("\\\\(Alpha|Beta|Gamma|Delta|Epsilon|Zeta|Eta|Theta|Iota|Kappa|Lambda|Mu|Nu|Xi|Omicron|Pi|Rho|Sigma|Tau|Upsilon|Phi|Chi|Psi|Omega|alpha|beta|gamma|delta|epsilon|zeta|eta|theta|iota|kappa|lambda|mu|nu|xi|omicron|pi|rho|sigma|tau|upsilon|phi|chi|psi|omega|sum|prod)", "&\\1;", x)
> - x <- psub("\\\\(dots|ldots)", "…", x)
> - x <- psub("\\\\(left|right)", "", x)
> - x <- psub("\\\\leq?", "≤", x)
> - x <- psub("\\\\geq?", "≥", x)
> - x <- psub("\\\\neq?", "≠", x)
> - x <- fsub("\\infty", "∞", x)
> - x <- fsub("\\sqrt", "√", x)
> + rx <- paste0("\\\\(",
> + paste(math_replacements[,"name"], collapse = "|"),
> + ")(?![a-zA-Z])")
> + m <- gregexec(rx, x, perl = TRUE)
> + ii <- lapply(regmatches(x, m),
> + function(mm) if (length(mm)) match(mm[2,], math_replacements[,"name"]))
> + regmatches(x, gregexpr(rx, x, perl = TRUE)) <- lapply(ii, function(i) math_replacements[i, "html"])
> }
> x
> }
> Index: src/library/tools/R/Rd2txt.R
> ===================================================================
> --- src/library/tools/R/Rd2txt.R (revision 90047)
> +++ src/library/tools/R/Rd2txt.R (working copy)
> @@ -55,6 +55,71 @@
> }
> })
> +math_replacements <- matrix(c(
> + "Alpha", "\u391", "Alpha", "Α",
> + "Beta", "\u392", "Beta", "Β",
> + "Gamma", "\u393", "Gamma", "Γ",
> + "Delta", "\u394", "Delta", "Δ",
> + "Epsilon", "\u395", "Epsilon", "Ε",
> + "Zeta", "\u396", "Zeta", "Ζ",
> + "Eta", "\u397", "Eta", "Η",
> + "Theta", "\u398", "Theta", "Θ",
> + "Iota", "\u399", "Iota", "Ι",
> + "Kappa", "\u39a", "Kappa", "Κ",
> + "Lambda", "\u39b", "Lambda", "Λ",
> + "Mu", "\u39c", "Mu", "Μ",
> + "Nu", "\u39d", "Nu", "Ν",
> + "Xi", "\u39e", "Xi", "Ξ",
> + "Omicron", "\u39f", "Omicron", "Ο",
> + "Pi", "\u3a0", "Pi", "Π",
> + "Rho", "\u3a1", "Rho", "Ρ",
> + "Sigma", "\u3a3", "Sigma", "Σ",
> + "Tau", "\u3a4", "Tau", "Τ",
> + "Upsilon", "\u3a5", "Upsilon", "Υ",
> + "Phi", "\u3a6", "Phi", "Φ",
> + "Chi", "\u3a7", "Chi", "Χ",
> + "Psi", "\u3a8", "Psi", "Ψ",
> + "Omega", "\u3a9", "Omega", "Ω",
> + "alpha", "\u3b1", "alpha", "α",
> + "beta", "\u3b2", "beta", "β",
> + "gamma", "\u3b3", "gamma", "γ",
> + "delta", "\u3b4", "delta", "δ",
> + "epsilon", "\u3b5", "epsilon", "ε",
> + "zeta", "\u3b6", "zeta", "ζ",
> + "eta", "\u3b7", "eta", "η",
> + "theta", "\u3b8", "theta", "θ",
> + "iota", "\u3b9", "iota", "ι",
> + "kappa", "\u3ba", "kappa", "κ",
> + "lambda", "\u3bb", "lambda", "λ",
> + "mu", "\u3bc", "mu", "μ",
> + "nu", "\u3bd", "nu", "ν",
> + "xi", "\u3be", "xi", "ξ",
> + "omicron", "\u3bf", "omicron", "ο",
> + "pi", "\u3c0", "pi", "π",
> + "rho", "\u3c1", "rho", "ρ",
> + "sigma", "\u3c3", "sigma", "σ",
> + "tau", "\u3c4", "tau", "τ",
> + "upsilon", "\u3c5", "upsilon", "υ",
> + "phi", "\u3c6", "phi", "φ",
> + "chi", "\u3c7", "chi", "χ",
> + "psi", "\u3c8", "psi", "ψ",
> + "omega", "\u3c9", "omega", "ω",
> + "sum", "\u2211", "sum", "∑",
> + "prod", "\u220f", "prod", "∏",
> + "sqrt", "\u221a", "sqrt", "√",
> + "dots", "\u2026", "...", "…",
> + "ldots", "\u2026", "...", "…",
> + "le", "\u2264", "<=", "≤",
> + "leq", "\u2264", "<=", "≤",
> + "ge", "\u2265", ">=", "≥",
> + "geq", "\u2265", ">=", "≥",
> + "ne", "\u2260", "!=", "≠",
> + "neq", "\u2260", "!=", "≠",
> + "infty", "\u221e", "Inf", "∞",
> + "left", "", "", "",
> + "right", "", "", ""
> +), ncol = 4, byrow = TRUE, dimnames = list(NULL, c("name", "fancy", "ascii", "html")))
> +
> transformMethod <- function(i, blocks, Rdfile) {
> editblock <- function(block, newtext)
> list(tagged(newtext,
> @@ -529,13 +594,14 @@
> }
> txt_eqn <- function(x) {
> - x <- psub("\\\\(Alpha|Beta|Gamma|Delta|Epsilon|Zeta|Eta|Theta|Iota|Kappa|Lambda|Mu|Nu|Xi|Omicron|Pi|Rho|Sigma|Tau|Upsilon|Phi|Chi|Psi|Omega|alpha|beta|gamma|delta|epsilon|zeta|eta|theta|iota|kappa|lambda|mu|nu|xi|omicron|pi|rho|sigma|tau|upsilon|phi|chi|psi|omega|sum|prod|sqrt)", "\\1", x)
> - x <- psub("\\\\(dots|ldots)", "...", x)
> - x <- psub("\\\\(left|right)", "", x)
> - x <- psub("\\\\leq?", "<=", x)
> - x <- psub("\\\\geq?", ">=", x)
> - x <- psub("\\\\neq?", "!=", x)
> - x <- fsub("\\infty", "Inf", x)
> + replacement <- if (unicode_symbols) "fancy" else "ascii"
> + rx <- paste0("\\\\(",
> + paste(math_replacements[,"name"], collapse = "|"),
> + ")(?![a-zA-Z])")
> + m <- gregexec(rx, x, perl = TRUE)
> + ii <- lapply(regmatches(x, m),
> + function(mm) if (length(mm)) match(mm[2,], math_replacements[,"name"]))
> + regmatches(x, gregexpr(rx, x, perl = TRUE)) <- lapply(ii, function(i) math_replacements[i, replacement])
> ## FIXME: are these needed?
> x <- psub("\\\\(bold|strong|emph|var)\\{([^}]*)\\}", "\\2", x)
> x <- psub("\\\\(code|samp)\\{([^}]*)\\}", "'\\2'", x)
> --
> Best regards,
> Ivan
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