From 50d6dd8b50958271bf1ff13f99dc21d4cd8431f7 Mon Sep 17 00:00:00 2001
From: Peter Mikkelsen <petermikkelsen10@gmail.com>
Date: Thu, 13 Jan 2022 19:45:22 +0000
Subject: Implement basic reference counting for arrays, which so they get
 freed when not in use anymore.

---
 eval.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

(limited to 'eval.c')

diff --git a/eval.c b/eval.c
index ae7dbd7..2eb5abd 100644
--- a/eval.c
+++ b/eval.c
@@ -104,7 +104,13 @@ retry:
 			errormsg = L"No reduce rule. Syntax error.";
 			return nil;
 		}else{
-			stmt->toks[offset] = fn(stmt->toks[offset],stmt->toks[offset+1]);
+			Datum new = fn(stmt->toks[offset],stmt->toks[offset+1]);
+			if(stmt->toks[offset].tag == ArrayTag)
+				freearray(stmt->toks[offset].array);
+			if(stmt->toks[offset+1].tag == ArrayTag)
+				freearray(stmt->toks[offset+1].array);
+
+			stmt->toks[offset] = new;
 			for(int i = offset+1; i < stmt->ntoks-1; i++)
 				stmt->toks[i] = stmt->toks[i+1];
 			stmt->ntoks--;
@@ -126,8 +132,13 @@ lookup(Datum var)
 	if(var.symbol->undefined){
 		errormsg = runesmprint("Variable undefined: %S\n", var.symbol->name);
 		return nil;
-	}else
-		return &var.symbol->value;
+	}else{
+		Datum *val = &var.symbol->value;
+		val->shy = 0;
+		if(val->tag == ArrayTag)
+			incref(val->array); /* since the value is now in the var AND in the code */
+		return val;
+	}
 }
 
 Datum
@@ -136,11 +147,13 @@ strand(Datum left, Datum right)
 	traceprint("Stranding (%d %d)\n", left.array->stranded, right.array->stranded);
 	Datum result;
 	result.shy = 0;
-	Array *leftarr = left.array->stranded ? left.array : fnEnclose(left.array);
-	Array *rightarr = right.array->stranded ? right.array : fnEnclose(right.array);
+	Array *leftarr = left.array->stranded ? fnSame(left.array) : fnEnclose(left.array);
+	Array *rightarr = right.array->stranded ? fnSame(right.array) : fnEnclose(right.array);
 	result.tag = ArrayTag;
 	result.array = fnCatenateFirst(leftarr, rightarr);
 	result.array->stranded = 1;
+	freearray(leftarr);
+	freearray(rightarr);
 	return result;
 }
 
@@ -159,14 +172,17 @@ monadfun(Datum left, Datum right)
 			Symbol *alpha = getsym(currentsymtab, L"⍺");
 			alpha->value.tag = ArrayTag;
 			alpha->value.array = left.func.left;
+			/* no need to increment refs, since it was done on binding the arg */
 			alpha->undefined = 0;
 		}
 
 		Symbol *omega = getsym(currentsymtab, L"⍵");
 		omega->value = right;
 		omega->undefined = 0;
+		incref(right.array);
 
 		Datum *dfnres = evalline(left.func.dfn);
+		freesymtab(currentsymtab);
 		currentsymtab = tmpsymtab;
 		return *dfnres; /* TODO what if the evaluation failed */
 	}else{
@@ -176,6 +192,10 @@ monadfun(Datum left, Datum right)
 		else
 			result.array = monadfunctiondefs[left.func.code](right.array);
 	}
+
+	if(left.func.left)
+		freearray(left.func.left);
+
 	return result;
 }
 
@@ -188,6 +208,7 @@ dyadfun(Datum left, Datum right)
 	result.tag = BoundFunctionTag,
 	result.func = right.func;
 	result.func.left = left.array;
+	incref(left.array);
 	return result;
 }
 
@@ -219,8 +240,11 @@ assign(Datum left, Datum right)
 {
 	left.symbol->value = right; /* TODO think about this*/
 	left.symbol->undefined = 0;
-	if(left.symbol->value.tag == ArrayTag)
+	if(left.symbol->value.tag == ArrayTag){
 		left.symbol->value.array->stranded = 0;
+		incref(right.array); /* for the binding */
+		incref(right.array); /* for the returned array */
+	}
 	right.shy = 1;
 	return right;
 }
\ No newline at end of file
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