readme tweaks.

README.md

@@ -2,7 +2,7 @@
 
 ## About
 
-This is a Lisp written in C. It follows the outline in this [Build Your Own Lisp](https://buildyourownlisp.com/chapter11_variables) book, though it then adds some small tweaks and improvements and quality of life improvements:
+This is a Lisp written in C. It follows the outline in this [Build Your Own Lisp](https://buildyourownlisp.com) book, though it then adds tweaks and quality of life improvements:
 
 - A makefile
 - Configurable verbosity levels
@@ -57,38 +57,54 @@ Simply call the `./mumble` binary:
 ```
 mumble> (1 2 3)
 mumble> { 1 2 3 }
-mumble> head (1 2 3)
-mumble> { head (1 2 3) }
+mumble> head {1 2 3}
+mumble> { head {1 2 3) }
 mumble> tail { 1 2 3 }
 mumble> list ( 1 2 3 )
 mumble> eval { head {1 2 3} } 
 mumble> (eval { head {+ tail head } } ) 1 2 3 
 mumble> len {1 2 3}
 mumble> join { {1 2} {3 4} }
-mumble> def { {x} { 100 } }
-mumble> x
-mumble> def { { a b c } { 1 2 3} }
-mumble> * a b c
-mumble> - a b c
-mumble> / a b c
-mumble> VERBOSITY=0
-mumble> VERBOSITY=1
+mumble> def {x} { 100 }
+mumble> def {y} 100
+mumble> (x y)
 mumble> VERBOSITY=2
 mumble> def {sq} (@ {x} {* x x})
 mumble> sq 44
+mumble> VERBOSITY=1
 mumble> def {sqsum} (@ {x y} {(+ (sq x) (sq y))})
 mumble> sqsum 2 3
+mumble> VERBOSITY=0
 mumble> def {init} (@ {xs} { list((head xs)) } )
+mumble> def {kopf} (@ {xx} { head (list xx) } )
 mumble> init {1 2}
+mumble> kopf (1 2)
+mumble> ifelse 1 2 3
+mumble> if 1 2 3
+mumble> ifelse 0 1 2 
+mumble> if 0 1 2 
+mumble> if {1 2 3} (1) (1)
+mumble> def {positive} (@ {x} {> x 0})
+mumble> def {fibtest} (@ {x} {if (> x 0) {+ x 1} 0 })
+mumble> fibtest 2
+mumble> def {fibonacci} (@ {x} {if (> x 1) { + (fibonacci (- x 2)) ( fibonacci ( - x 1 ) ) } 1} )
+mumble> fibonacci 4
+mumble> def {!} (@ {x} { if ( > 1 x) 1 { * x (! (- x 1)) } })
+mumble> ! 100
+mumble> def {++} (@ {x} { if ( > 1 x) 0 { + x (++ (- x 1)) } })
+mumble> ++ 10
+mumble>  def {++2} (@ {x} { / (* x (+ x 1)) 2 })
+mumble> ++2 10
+
 ```
 
+## To do
+
+- [x] Define functions
+- [x] Define if, = and >
+- [x] Build fibonacci function
+- [x] Build factorial function
 
 ## Gotchas
 
-This doesn't currently run on Windows. But it easily could, with [preprocessor statements from the book].
-
-## Usage and licensing
-
-I don't expect this project to be such that people might want to use it. If you want a
-
-But for the eventuality, this code is licensed under the MIT license; see the license.txt file.
+This doesn't currently run on Windows. But it easily could, with the preprocessor staments from parsing.c [here](https://buildyourownlisp.com/chapter6_parsing).

notes/savepoint.txt

@@ -1,3 +1,4 @@
 https://buildyourownlisp.com/chapter7_evaluation#trees
 https://buildyourownlisp.com/chapter9_s_expressions
 https://buildyourownlisp.com/chapter12_functions
+https://buildyourownlisp.com/chapter13_conditionals

src/mumble.c

@@ -782,7 +782,6 @@ lispval* builtin_join(lispval* l, lispenv* e)
 // Define a variable
 lispval* builtin_def(lispval* v, lispenv* env)
 {
-    // Takes one argument: def { { a b } { 1 2 } }
     // Takes two arguments: argument: def {a} 1; def {init} (@ {x y} {x})
     lispval* symbol_wrapper = v->cell[0];
     lispval* value = v->cell[1];
@@ -834,6 +833,77 @@ lispval* builtin_define_lambda(lispval* v, lispenv* env)
     lispval* lambda = lispval_lambda_func(variables, manipulation, new_env);
     return lambda;
 }
+
+// Conditionals
+
+lispval* builtin_ifelse(lispval* v, lispenv* e)
+{
+    // ifelse 1 {a} b
+    LISPVAL_ASSERT(v->count == 3, "Error: function ifelse passed too many arguments. Try ifelse choice result alternative, e.g., if (1 (a) {b})");
+
+    lispval* choice = v->cell[0];
+    lispval* result = v->cell[1];
+    lispval* alternative = v->cell[2];
+		
+		if( choice->type == LISPVAL_NUM && choice->num == 0){
+			lispval* answer = clone_lispval(alternative);
+			if(answer->type == LISPVAL_QEXPR){
+				answer->type = LISPVAL_SEXPR;
+				answer = evaluate_lispval(answer, e);
+			}
+			return answer;
+		}else {
+			lispval* answer = clone_lispval(result);
+			if(answer->type == LISPVAL_QEXPR){
+				// answer = builtin_eval(answer, e);
+				answer->type = LISPVAL_SEXPR;
+				answer = evaluate_lispval(answer, e);
+			}
+			return answer;
+		}
+}
+
+// Comparators: =, > (also potentially <, >=, <=, <=)
+// For numbers. 
+
+lispval* builtin_equal(lispval* v, lispenv* e)
+{
+    // ifelse 1 {a} b
+    LISPVAL_ASSERT(v->count == 2, "Error: function = takes two numeric arguments. Try (= 1 2)");
+
+    lispval* a = v->cell[0];
+    lispval* b = v->cell[1];
+	  
+		LISPVAL_ASSERT(a->type == LISPVAL_NUM, "Error: Functio = only takes numeric arguments.");
+		LISPVAL_ASSERT(b->type == LISPVAL_NUM, "Error: Functio = only takes numeric arguments.");
+
+		if(a->num == b->num){
+			return lispval_num(1);
+		}else {
+			return lispval_num(0);
+		}
+}
+
+
+lispval* builtin_greater_than(lispval* v, lispenv* e)
+{
+    // ifelse 1 {a} b
+    LISPVAL_ASSERT(v->count == 2, "Error: function = takes two numeric arguments. Try (= 1 2)");
+
+    lispval* a = v->cell[0];
+    lispval* b = v->cell[1];
+	  
+		LISPVAL_ASSERT(a->type == LISPVAL_NUM, "Error: Functio = only takes numeric arguments.");
+		LISPVAL_ASSERT(b->type == LISPVAL_NUM, "Error: Functio = only takes numeric arguments.");
+
+		if(a->num > b->num){
+			return lispval_num(1);
+		}else {
+			return lispval_num(0);
+		}
+}
+
+
 // Simple math ops
 lispval* builtin_math_ops(char* op, lispval* v, lispenv* e)
 {
@@ -931,8 +1001,13 @@ void lispenv_add_builtins(lispenv* env)
     lispenv_add_builtin("tail", builtin_tail, env);
     lispenv_add_builtin("eval", builtin_eval, env);
     lispenv_add_builtin("join", builtin_join, env);
+    lispenv_add_builtin("len", builtin_len, env);
     lispenv_add_builtin("def", builtin_def, env);
     lispenv_add_builtin("@", builtin_define_lambda, env);
+    lispenv_add_builtin("ifelse", builtin_ifelse, env);
+    lispenv_add_builtin("if", builtin_ifelse, env);
+    lispenv_add_builtin("=", builtin_equal, env);
+    lispenv_add_builtin(">", builtin_greater_than, env);
 }
 
 // Evaluate the lispval