initial calculator code

src/calc.c

@@ -0,0 +1,98 @@
+/*
+ * calc.c
+ *
+ *  Created on: Mar 28, 2019
+ */
+
+#include "decn/decn.h"
+
+#define STACK_SIZE 4 //must be a power of 2
+
+#define STACK_X 0
+#define STACK_Y 1
+#define STACK_Z 2
+#define STACK_T 3
+
+//stack "grows" towards 0
+__xdata dec80 Stack[STACK_SIZE]; //0->x, 1->y, 2->z, 3->t initially
+uint8_t StackPtr = 0;
+
+#define stack(x) Stack[(StackPtr + (x)) & (STACK_SIZE-1)]
+
+static void pop(){
+	copy_decn(&stack(STACK_X), &stack(STACK_T)); //duplicate t into x (which becomes new t)
+	StackPtr++; //adjust pointer
+}
+
+void push_decn(const char* signif_str, int16_t exponent, uint8_t no_lift){
+	if (!no_lift){
+		StackPtr--;
+	}
+	build_dec80(&stack(STACK_X), signif_str, exponent);
+}
+
+void clear_x(void){
+	set_dec80_zero(&stack(STACK_X));
+}
+
+void set_x(const char* signif_str, int16_t exponent){
+	build_dec80(&stack(STACK_X), signif_str, exponent);
+}
+
+__xdata dec80* get_x(void){
+	return &stack(STACK_X);
+}
+__xdata dec80* get_y(void){
+	return &stack(STACK_Y);
+}
+
+static void do_binary_op(void (*f_ptr)(dec80*, const dec80*)){
+	f_ptr(&stack(STACK_Y), &stack(STACK_X));
+	pop();
+}
+
+void process_cmd(char cmd){
+	//process cmd
+	switch(cmd){
+		//////////
+		case '+':{
+			do_binary_op(add_decn);
+		} break;
+		//////////
+		case '*':{
+			do_binary_op(mult_decn);
+		} break;
+		//////////
+		case '-':{
+			negate_decn(&stack(STACK_X));
+			do_binary_op(add_decn);
+		} break;
+		//////////
+		case '/':{
+			do_binary_op(div_decn);
+		} break;
+		//////////
+		case '=':{
+			StackPtr--;
+			copy_decn(&stack(STACK_X), &stack(STACK_Y));
+		} break;
+		//////////
+		case 'c':{
+			set_dec80_zero(&stack(STACK_X));
+		} break;
+		//////////
+		case '<':{ //use as +/-
+			negate_decn(&stack(STACK_X));
+		} break;
+		//////////
+		case 'r':{ //use as swap
+			dec80 tmp;
+			copy_decn(&tmp, &stack(STACK_X));
+			copy_decn(&stack(STACK_X), &stack(STACK_Y));
+			copy_decn(&stack(STACK_Y), &tmp);
+		} break;
+		//////////
+	} //switch(cmd)
+}
+
+