Skeleton

recursiveDescentParsers/cplusplus/interpreter/Makefile

+# This Makefile made available to his students by 
+# Prof. Ronald Moore  
+#     https://fbi.h-da.de/personen/ronald-moore/  
+#     mailto:ronald.moore@h-da.de
+# with no warranties whatsoever
+
+
+PROGS := interpreter
+
+# Uncomment only one of the next two lines (choose your c++ compiler)
+# CC=g++
+CC := clang++
+
+## Add your own CFLAGS if you find them necessary... such as -O3 or so... 
+CFLAGS :=  
+
+
+## More preliminaries
+# See https://www.gnu.org/software/make/manual/html_node/Special-Targets.html
+# In this makefile, we want to keep going even if we find errors
+.IGNORE :
+
+# Tell make that the following "targets" are "phony"
+# Cf. https://www.gnu.org/software/make/manual/html_node/Phony-Targets.html#Phony-Targets
+.PHONY : all clean
+
+##  Now, the targets -- the things that will get made!
+
+all: $(PROGS)
+
+$(PROGS): %: %.cpp
+	$(CC) -g $< $(CFLAGS) -o $@
+
+clean: 
+	$(RM) -fv *~ *.o $(PROGS)
+

recursiveDescentParsers/cplusplus/interpreter/README.md

+Contents
+========
+
+Everything here is taken from the slides for the "Compiler Construction"
+course, i.e. it is directly from Prof. Ronald C. Moore.
+
+Or at least, after all this time, I really don't remember having stolen
+this code from somewhere else, but if you find an older copy that looks
+similar, please let me know, so I can give credit where credit is due --
+or disavow knowledge of that source (as the case may be).
+
+You are in the following subdirectory 
+  ** `interpreter`  
+     This code take mathematical expressions and evaluates them,
+     i.e. it outputs numbers.
+     
+See **Chapter 1 Front End Construction**, Slides 21 and 22 (and please let me know when the inevitable day comes that these slide numbers are no longer correct).
+
+Ronald Moore  
+https://fbi.h-da.de/personen/ronald-moore/  
+ronald.moore@h-da.de
+ 
+
+30 April 2020 
+

recursiveDescentParsers/cplusplus/interpreter/interpreter.cpp

+// This code made available to his students by 
+// Prof. Ronald Moore  
+//     https://fbi.h-da.de/personen/ronald-moore/  
+//     mailto:ronald.moore@h-da.de
+// with no warranties whatsoever
+//
+// The grammar we are going to parse here is:
+// Grammar:
+// 	E	→ T E´
+// 	E´	→ + T E´  | - T E´ | ε
+// 	T	→ F T´
+// 	T´	→ * F T´  |  / F T´  |  ε
+// 	F	→ ( E ) | num
+// where the following are taken to be tokens:
+// left and right parenthesis, the plus and minus characters,
+// as well as asterisk and forward slash -- and numbers.
+// In the script, substraction and division are not supported,
+// but it seems like time to add them.
+//
+// Note that the recursive descent function for (e.g.) E´ 
+// is nameded "E2ndHalf"-
+
+#include <cstdio>
+#include <cstdlib>
+#include <string>
+#include <vector>
+
+// Preliminaries and Utilities
+// ============================
+
+// global variables -- sue me if you don't like that!
+std::string	currentLine( "" );
+int		currentLineNumber = 0;
+int		currentColumnNumber = 0;
+int		currentTokenLength = 0;
+// Utility Types
+typedef double numberType; // feel fee to change this to something else like int or float or bigint....
+
+// the tokens
+enum Token { 
+	tok_number,
+	tok_lparen,
+	tok_rparen,
+	tok_plus,
+	tok_minus,
+	tok_times,
+	tok_div
+} next_token; // again with the global variables... 
+
+// The Lexer
+// ==========
+
+	
+// main (!)
+// =========
+
+int main( int argc, char **argv ) {
+
+	return 0; // Alles klar!!!
+}