Recognise usual functions even without the leading '\'

Makefile

@@ -1,7 +1,7 @@
 SOURCES = $(wildcard *.md)
 OUT = $(SOURCES:.md=.pdf)
 
-HS_FILTERS_NAMES = nice-frac
+HS_FILTERS_NAMES = nice-frac usual-fun
 PY_FILTERS_NAMES = pandoc-svg.py
 EXT_FILTERS = pandoc-crossref
 
@@ -13,11 +13,11 @@ FILTERS = $(PY_FILTERS) $(HS_FILTERS) $(EXT_FILTERS)
 
 all: $(HS_FILTERS) $(OUT)
 
-$(OUT): $(SOURCES)
-	pandoc --smart -t latex $< $(addprefix --filter=, $(FILTERS)) -o $@
+$(OUT):
+	pandoc -S -t latex $(basename $@).md $(addprefix --filter=, $(FILTERS)) -o $@
 
-$(HS_FILTERS): $(addsuffix .hs, $(HS_FILTERS))
-	ghc --make -O2 $< -o $@	
+$(HS_FILTERS):
+	ghc --make $@.hs -o $@	
 
 clean:
 	rm -f $(OUT)

README.md

@@ -12,14 +12,14 @@ Includes various Pandoc filters:
 * Include [pandoc-crossref](https://github.com/lierdakil/pandoc-crossref) for
 easy numbering and referencing.
 
-* Convert fractions like "(n/k)" to "\frac{n}{k}" when n and k are integers in
-  math environment.
+* Convert simple fractions like "(n / k)" to LaTeX's "\\frac{n}{k}" when n and
+k are integers in a math environment.
+
+* automatically convert function names (cos, sin, exp, log) to their
+LaTeX equivalent (\\cos and so on) when in a mathematical environment,
+then taking out the useless leading `\`.
 
 ## TODO
 
-* automatically convert function names (cos, sin, exp, log) to their
-LaTeX equivalent (\cos and so on) when in a mathematical environment,
-then taking out the useless leading `\`.
-
 * anything else like this that could help writing more readable LaTeX
 code :)

filters/nice-frac.hs

@@ -9,12 +9,12 @@ space = "[ \\t\\n\\r]*"
 num :: String
 num = "([0-9]+)"
 
--- Substitute latex fractions like '\frac{42}{1}' for (42 / 1)
+-- Replace fractions like "(42 / 1)" by "\frac{42}{1}" 
 fracReg :: Regex
 fracReg = mkRegex $
-  "\\(" ++ space ++ num ++ space ++ "/" ++ space ++ num ++ "\\)"
+  "\\(" ++ space ++ num ++ space ++ "/" ++ space ++ num ++ space ++ "\\)"
 frac :: String -> String
-frac s = subRegex fracReg s "\\frac{\\1}{\\2}"
+frac s = subRegex fracReg s "\\\\frac{\\1}{\\2}"
 
 -- Apply the substitution to all Latex parts on the AST
 niceFrac :: Inline -> Inline

filters/usual-fun.hs

@@ -0,0 +1,33 @@
+-- usual-fun.hs
+
+import Text.Pandoc.JSON
+import Text.Regex
+import Data.List (intercalate)
+
+-- Association list for usual functions
+usual :: String
+usual = intercalate "|" [
+  "cos", "sin", "tan", "cotan",
+  "arccos", "arcsin", "arctan",
+  "exp", "log"]  
+
+-- Remove the '\' before usual functions' names if present
+rmBSReg :: Regex
+rmBSReg = mkRegex $ "(\\\\)(" ++ usual ++ ")\\>"
+rmBS :: String -> String
+rmBS s = subRegex rmBSReg s "\\2"
+
+-- Add a '\' before usual functions' names
+addBSReg :: Regex
+addBSReg = mkRegex $ "\\<(" ++ usual ++ ")\\>"
+addBS :: String -> String
+addBS s = subRegex addBSReg s "\\\\\\0"
+
+-- Apply the substitution to all Latex parts on the AST
+niceFrac :: Inline -> Inline
+niceFrac (Math t s) = Math t (addBS . rmBS $ s)
+niceFrac x = x
+
+main :: IO ()
+main = toJSONFilter niceFrac
+