Add basic code for parser/evaluator. Can do simple stranding

1 files changed, 80 insertions, 2 deletions

diff --git a/eval.c b/eval.c
index baabf21..9c737ff 100644
--- a/eval.c
+++ b/eval.c
@@ -6,10 +6,88 @@
 
 Rune *errormsg;
 
+typedef Datum (*evalfn)(Datum, Datum);
+
+Datum strand(Datum, Datum);
+
+int bindingstrengths[12][12] = {
+/*	A  F  H  MO DO AF (  )  {  }  [  ] */
+	1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* A */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* H */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* MO */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* DO */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* FA */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* ( */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* ) */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* { */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* } */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* [ */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* ] */
+};
+
+evalfn evalfns[12][12] = {
+/*	A  F  H  MO DO AF (  )  {  }  [  ] */
+	strand, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* A */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* H */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* MO */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* DO */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* FA */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* ( */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* ) */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* { */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* } */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* [ */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* ] */
+};
+
+
 Datum *
 eval(Datum *tokens, int *ntoks)
 {
-	*ntoks = 0;
-	errormsg = L"Evaluator not written yet";
+	while(*ntoks > 1){
+		int maxlevel = 0;
+		int offset;
+		evalfn fn = nil;
+		print("CURRENT: %S\n", ppdatums(tokens, *ntoks));
+		for(offset = (*ntoks)-1; offset >= 0; offset--){
+			int level;
+			if(offset == 0)
+				level = 0;
+			else{
+				Datum left = tokens[offset-1];
+				Datum right = tokens[offset];
+				level = bindingstrengths[left.tag][right.tag];
+			}
+			if(level < maxlevel){
+				Datum left = tokens[offset];
+				Datum right = tokens[offset+1];
+				fn = evalfns[left.tag][right.tag];
+				print("Reducing %S and %S\n", ppdatum(left), ppdatum(right));
+				break;
+			}else if(level > maxlevel)
+				maxlevel = level;
+		}
+		if(maxlevel == 0){
+			errormsg = L"No reduce rule. Syntax error.";
+			*ntoks = 0;
+		}else{
+			tokens[offset] = fn(tokens[offset],tokens[offset+1]);
+			for(int i = offset+1; i < (*ntoks)-1; i++)
+				tokens[i] = tokens[i+1];
+			(*ntoks)--;
+		}
+	}
 	return tokens;
+}
+
+Datum
+strand(Datum left, Datum right)
+{
+	print("Stranding\n");
+	Datum result;
+	result.tag = ArrayTag;
+	result.array = fnCatenateFirst(left.array,fnEnclose(right.array));
+	return result;
 }
\ No newline at end of file