yoxem/one-variable-linear-equation-solver
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Tan, Kian-ting 2018-05-21 01:56:44 +08:00
parent 2637899ed7
commit 977cb2a9ae
2 changed files with 108 additions and 23 deletions
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1
interp.l
View file

@ -22,7 +22,6 @@ var ([_]|{alpha})([_]|{alpha}|{dig})*
{ws} {yycharno = yycharno + yyleng;} {ws} {yycharno = yycharno + yyleng;}
{var} {yylval.strVal = strdup(yytext); {var} {yylval.strVal = strdup(yytext);
yycharno = yycharno + yyleng; yycharno = yycharno + yyleng;
printf("yyval.strVal = %s",yylval.strVal);
return T_VAR;} return T_VAR;}
{number} {yylval.floatVal = atof(yytext); {number} {yylval.floatVal = atof(yytext);
yycharno = yycharno + yyleng; yycharno = yycharno + yyleng;

126
interp.y
View file

@ -1,12 +1,16 @@
%{ %{
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
void yyerror(const char* msg) {} #include <math.h>
#include <string.h>
void yyerror(const char* msg);
extern FILE* yyin; extern FILE* yyin;
extern int yylex();
typedef enum typedef enum
{null, opera, var, val} NodeType; {null, opera, var, val} NodeType;
typedef enum {false, true} bool;
typedef struct Node { typedef struct Node {
float val; float val;
char * name; // val_name char * name; // val_name
@ -60,21 +64,23 @@ void run_through_tree (Node *node){
} }
} }
bool escape_recursion = false;
float eval_node(float var_val, Node * node){ float eval_node(float var_val, Node * node){
switch ((*node).node_type){ switch ((*node).node_type){
case var: case var:
if (var_name == ""){ if (strcmp(var_name,"")==0){
var_name = node->name; var_name = node->name;
printf("%s",node->name);
return var_val; return var_val;
} }
else if (var_name == node->name){ else if (strcmp(var_name,node->name)==0){
return var_val; return var_val;
} }
else{ else{
printf("Error: Too many variable, eg. %s, %s.\n", printf("Error: Too many variable, eg. %s, %s.\n",
var_name,node->name); var_name,node->name);
escape_recursion = true;
return NAN;
break; break;
} }
@ -83,26 +89,85 @@ float eval_node(float var_val, Node * node){
case val: case val:
return (*node).val; return (*node).val;
break; break;
case opera: case opera:{
float left_num, right_num;
left_num = eval_node(var_val,node->left);
if (escape_recursion){return NAN; break;}
right_num = eval_node(var_val,node->right);
if (escape_recursion){return NAN; break;}
if (node->opr == "+"){ if (node->opr == "+"){
return (eval_node(var_val,node->left) + eval_node(var_val,node->right)); return left_num + right_num;
} }
else if (node->opr == "-"){ else if (node->opr == "-"){
return (eval_node(var_val,node->left) - eval_node(var_val,node->right)); return left_num - right_num;
} }
else if (node->opr == "*"){ else if (node->opr == "*"){
return (eval_node(var_val,node->left) * eval_node(var_val,node->right)); return left_num * right_num;
} }
else if (node->opr == "/"){ else if (node->opr == "/"){
return (eval_node(var_val,node->left) / eval_node(var_val,node->right)); return left_num / right_num;
} }
break; break;}
} }
} }
Node * main_node; Node * main_node;
float solve(Node * m_node){
escape_recursion = false;
var_name = "";
float x0 = 0.0;
float y0 = eval_node(x0,m_node);
float x1 = 1.0;
float y1 = eval_node(x1,m_node);
float x2 = 10.0;
float y2 = eval_node(x2,m_node);
if (isnan(y0) || isnan(y1) || isnan(y2)){
return NAN;
}
else if(strcmp(var_name,"")==0){
var_name = "[var]";
if (y0 == 0.0){
printf("%s can be any numbers; the following is just a solution.",
var_name);
return 0.0;
}
else{
return NAN;
}
}
else{
float slope1 = (y1-y0) / (x1-x0);
float slope2 = (y2-y0) / (x2-x0);
if (slope1 == slope2){
if (slope1 == 0.0){
if (y0 == 0){
printf("%s can be any numbers; the following is just a solution.",
var_name);
return 0.0;
}
else{
return NAN;
}
}
else{
float ans = -y0 / slope1;
return ans;
}
}
else{
printf("Error: the formula is not linear.\n");
return NAN;
}
}
}
%} %}
%union{ %union{
@ -126,15 +191,23 @@ Node * main_node;
%% %%
S : S E T_NEWLINE { main_node = $2;run_through_tree(main_node); /*printf("TOTAL_VALUE: %f",eval_node(5.0,main_node));*/} S : S E T_NEWLINE { main_node = $2;
printf("ANSWER: %s = %f",var_name,solve(main_node));}
| {} | {}
; ;
E : E T_ADD E {Node * op_node = (Node *) malloc(sizeof(Node));*op_node = create_op_node("+"); connect_node(op_node,$1,$3);$$ = op_node;} E : E T_ADD E {Node * op_node = (Node *) malloc(sizeof(Node));
| E T_SUB E {Node * op_node = (Node *) malloc(sizeof(Node));*op_node = create_op_node("-"); connect_node(op_node,$1,$3);$$ = op_node;} *op_node = create_op_node("+");
| E T_MUL E {Node * op_node connect_node(op_node,$1,$3);$$ = op_node;}
= (Node *) malloc(sizeof(Node));*op_node = create_op_node("*"); connect_node(op_node,$1,$3);$$ = op_node;} | E T_SUB E {Node * op_node = (Node *) malloc(sizeof(Node));
| E T_DIV E {Node * op_node = (Node *) malloc(sizeof(Node));*op_node = create_op_node("/"); connect_node(op_node,$1,$3);$$ = op_node;} *op_node = create_op_node("-");
connect_node(op_node,$1,$3);$$ = op_node;}
| E T_MUL E {Node * op_node = (Node *) malloc(sizeof(Node));
*op_node = create_op_node("*");
connect_node(op_node,$1,$3);$$ = op_node;}
| E T_DIV E {Node * op_node = (Node *) malloc(sizeof(Node));
*op_node = create_op_node("/");
connect_node(op_node,$1,$3);$$ = op_node;}
| T_SUB E %prec NEG { | T_SUB E %prec NEG {
Node * op_node = (Node *) malloc(sizeof(Node)); Node * op_node = (Node *) malloc(sizeof(Node));
Node * zero_node = (Node *) malloc(sizeof(Node)); Node * zero_node = (Node *) malloc(sizeof(Node));
@ -142,8 +215,12 @@ E : E T_ADD E {Node * op_node = (Node *) malloc(sizeof(Node));*op_node = cre
* op_node = create_op_node("-"); * op_node = create_op_node("-");
connect_node(op_node,zero_node,$2); connect_node(op_node,zero_node,$2);
$$ = op_node;} $$ = op_node;}
| T_NUM {Node * val_node = (Node *) malloc(sizeof(Node));* val_node = create_val_node($1); $$ = val_node;} | T_NUM {Node * val_node = (Node *) malloc(sizeof(Node));
| T_VAR {Node * var_node = (Node *) malloc(sizeof(Node));* var_node = create_var_node($1); $$ = var_node;} * val_node = create_val_node($1);
$$ = val_node;}
| T_VAR {Node * var_node = (Node *) malloc(sizeof(Node));
* var_node = create_var_node($1);
$$ = var_node;}
| T_LPATH E T_RPATH {$$ = $2;} | T_LPATH E T_RPATH {$$ = $2;}
; ;
@ -152,9 +229,18 @@ E : E T_ADD E {Node * op_node = (Node *) malloc(sizeof(Node));*op_node = cre
int main(){ int main(){
yyin = stdin; yyin = stdin;
do{ do{
printf(
"A program to solve f(x) = 0 such that f(x) is a 1-var linear function.\n");
printf("Please Enter a 1-var linear function: ");
yyparse(); yyparse();
}while(!feof(yyin)); }while(!feof(yyin));
return 0; return 0;
} }
void yyerror (const char *msg)
{
fprintf (stderr, "%s\n", msg);
}