Merge branch 'latex'

.gitignore

@@ -1 +1,4 @@
-__pycache__
+__pycache__
+.DS_Store
+
+

README.md

@@ -91,6 +91,24 @@ the output will be displayed on the console:
         (1)     (2)
 ```
 
+# Latex
+`lat.py` module allows you to convert from python math expressions to latex codes. For instance:
+```python
+tree = build("2+pi*sin(x+2)/cos(x^(y+1))")  # Build a ast first
+lat_expr = tolat(expr)                      # Convert to latex code
+# The output will be:
+# ${2+\frac{{\pi*sin({x+2})}}{cos({x^{y+1}})}}$
+```
+Furthermore, you can generate .tex file by given latex code. The file will only contains the header, footer and the given expression:
+```python
+totex(lat_expr, "/location")   # Save the .tex file to given location with name
+```
+After that, a pdf file can be generated by compiling the .tex file
+<b>(Please make sure you have pdflatex installed)</b>
+```python
+topdf("/location", "/target")   # Compiling .tex file from source and save the files to target location
+```
+
 # Operations
 Here are some symbols and special numbers that AST supports:
 

lat.py

@@ -0,0 +1,92 @@
+import ast
+import subprocess
+import os
+from expr import is_number, is_letter, is_func, is_unary
+
+
+header = r'''\documentclass{standalone}
+\begin{document}
+'''
+
+
+footer = r'''\end{document}'''
+
+
+latex_mapper = {
+    "/" : lambda x,y : "\\frac{"+x+"}{"+y+"}"
+}
+
+
+special_mapper = {
+    "pi" : lambda x : "\\pi"
+}
+
+
+def tolat(a):
+    """Convert a AST to latex format code, so that a pdf of the
+    given formula can be generated.
+    """
+    def _eval(n):
+        if n is None:
+            return ''
+        if n.sym in special_mapper:
+            return special_mapper[n.sym](n.sym)
+        if is_number(n.sym) or (is_letter(n.sym) and not is_func(n.sym)):
+            return n.sym
+        left = _eval(n.left)
+        right = _eval(n.right)
+        if n.sym in latex_mapper:
+            return latex_mapper[n.sym](left, right)
+        elif is_unary(n.sym):
+            return n.sym + '(' + _eval(n.right) + ')'
+        else:
+            return '{'+left + n.sym + right+'}'
+    return '$'+_eval(a.root)+'$'
+
+
+def totex(lat, loc):
+    """Convert a snippet of the latex code to a complete latex code by
+    adding header and footer. And save the file as .tex format to the
+    given location, or create new file if it does not exist. If the
+    header and footer were not added, the compile phase will fail.
+    """
+    code = header + lat + footer
+    with open(loc, "w+") as f:
+        f.write(code)
+
+
+def topdf(source, des, rm=False):
+    """Compile the .tex file from given source location 
+    and save the result to the given file destination.
+    If rm is enabled, all files except for the pdf file
+    will be removed after the compilation.
+    """
+    command = ["pdflatex", "-output-directory", des, source]
+    subprocess.call(command)
+    if rm:
+        from os import listdir, remove
+        from os.path import isfile, join, splitext, basename
+        name = splitext(basename(source))[0]
+        for f in listdir(des):
+            if isfile(join(des, f)):
+                fname, ext = splitext(f)
+                if fname == name and ext != ".pdf":
+                    remove(os.path.join(des, f))
+
+
+def fastpdf(a, des, name, rm=False):
+    """Fastest way to generate a pdf from given AST and without
+    saving .tex file or anything. Calling this method will directly
+    generate the pdf file. If rm is enabled, all files except for
+    the pdf file will be removed after the compilation.
+    """
+    latex = tolat(a)
+    totex(latex, os.path.join(os.path.curdir, name+".tex"))
+    topdf(os.path.join(os.path.curdir, name+".tex"), des, rm=rm)
+    p = os.path.join(os.path.curdir, name+".tex")
+    if os.path.isfile(p):
+        os.remove(p)
+
+
+# a = ast.build("2+pi*sin(x+2)/cos(x^(y+1))")
+# fastpdf(a, "/Users/danielxu/Desktop/github/pexpr", "example", rm=True)