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Compilers
Lecture 19:
Semantic Analysis II
Dr. Javier Gonzalez-Sanchez
jgonzalezs@up.edu.mx
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Previously …
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Semantic Analysis
1. Declaration and Unicity. Review for uniqueness and that the
variable has been declared before its usage.
2. Types. Review that the types of variables match the values assigned
to them.
3. Array’s indexes. Review that the indexes are integers.
4. Conditions. Review that all expressions on the conditions return a
boolean value.
5. Return type. Review that the value returned by a method matches
the type of the method.
6. Parameters. Review that the parameters in a method match the
type and number with the declaration of the method.
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Symbol Table
int i;
char j; int m;
void method(int n, char c) {
int n; short l;
i = j; i = m;
}
void method() {
int i = 5;
int j = i + i;
}
int k;
int method(int i) {
if (i>5) { ++i; }
while (i + 1) { ++i; }
do {++i; } while (i);
for (i = 0; m; ++i) {
k++;
}
}
name type scope value
i int global
j char global
m int global
method-int-char void function
n int method-int-char
l short method-int-char
method void function
i int method
j int method
k int global
method-int int function
i Int method-int
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Next
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Semantic Analysis
1. Declaration and Unicity. Review for uniqueness and that the
variable has been declared before its usage.
2. Types. Review that the types of variables match the values assigned
to them.
3. Array’s indexes. Review that the indexes are integers.
4. Conditions. Review that all expressions on the conditions return a
boolean value.
5. Return type. Review that the value returned by a method matches
the type of the method.
6. Parameters. Review that the parameters in a method match the
type and number with the declaration of the method.
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Type matching | Example 1
int x, y, z;
char p, q, r;
float a, b, c;
boolean foo;
void method() {
x = a * c + p;
}
x
*
+
a c p
=
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Type matching | Cube
fill one sheet for
each operator in
the language
cube
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Type matching | Cube
OPERATOR int float char strin
g
boolea
n
void
int
float
char
string
boolean
void
cube
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Type matching | Cube
OPERATOR
+
int float char strin
g
boolea
n
void
int int float X string X X
float float float X string X X
char X X X string X X
string string string string string string X
boolean X X X string X X
void X X X X X X
cube
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Type matching | Cube
OPERATOR
&
int float char strin
g
boolea
n
void
int X X X X X X
float X X X X X X
char X X X X X X
string X X X X X X
boolean X X X X boolean X
void X X X X X X
cube
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Type matching | Cube
OPERATOR
<
int float char string boolean void
int boolea
n
boolea
n
X X X X
float boolea
n
boolea
n
X X X X
char X X X X X X
string X X X X X X
boolean X X X X X X
void X X X X X X
cube
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Type matching | Cube
OPERATOR
=
int float char strin
g
boolea
n
void
int OK X X X X X
float OK OK X X X X
char X X OK X X X
string X X X OK X X
boolean X X X X OK X
void X X X X X OK
cube
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Type matching | Cube
OPERATOR
-
int float char strin
g
boolea
n
void
int float X X X X
cube (- unary)
OPERATOR
+
int float char strin
g
boolea
n
void
int int float X string X X
float float float X string X X
char X X X string X X
string string string string string string X
boolean X X X string X X
void X X X X X X
cube (- binary)
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Type matching | Example 1
int x, y, z;
char p, q, r;
float a, b, c;
boolean foo;
void method() {
x = a * c + p;
}
x
*
+
a c p
=
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Type matching | Example 2
int a;
int c (int b) {
return b * 3 * 2 * 1 ;
}
void main () {
a = 1;
boolean a= c(14)/2 > 1;
}
cube for
matching types
symbol table
stack
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Programming Assignment 3
Level 2
Reviewing Type Matching
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Handwritten Notes
/
/ Definition of the cube of types and operators
int cube [][][];
public static int OP_PLUS = 1;
public static int OP_MINUS = 2;
public static int OP_MULT = 3;
/
/ …
public static int INTEGER = 1;
public static int FLOAT = 2;
/
/ …
cube [OP_PLUS][INTEGER][INTEGER] = INTEGER;
cube [OP_PLUS][FLOAT][INTEGER] = FLOAT;
cube [OP_PLUS][INTEGER][FLOAT] = FLOAT;
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Error Recovery
PROGRAM
BODY
ASSIGNMENT
VARIABLE
WHILE
IF
RETURN
PRINT
C
EXPRESSION
X
Y
R
E
A
B
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Assignment 2 | Code
C
1.
/
/ except for the open parenthesis
SemanticAnalizer.pushStack(
tokens.get(currentToken).getToken()
);
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Parser
1. Store in a flag (operatorWasUSed):
Did the operator ‘-’ exist?
2.
if (operatorWasUsed)
String x = SemanticAnalizer.popStack();
String result = SemanticAnalizer.checkCube (x, “-” );
SemanticAnalizer.pushStack(result);
}
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Parser
1. Store in a flag (twiceHere):
Did we pass this point twice?
3.
if (twiceHere)
String x = SemanticAnalizer.popStack();
String y = SemanticAnalizer.popStack();
String result = SemanticAnalizer.checkCube (x, y, operator );
SemanticAnalizer.pushStack(result);
twiceHere = false; /
/ reset the flag
}
2. Store the operator that
creates the loop?
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Parser
1. Store in a flag (twiceHere):
Did we pass this point twice?
3.
if (twiceHere)
String x = SemanticAnalizer.popStack();
String y = SemanticAnalizer.popStack();
String result = SemanticAnalizer.checkCube (x, y, operator );
SemanticAnalizer.pushStack(result);
twiceHere = false; /
/ reset the flag
}
2. Store the operator that
creates the loop?
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Parser
1. Store in a flag (twiceHere):
Did we pass this point twice?
3.
if (twiceHere)
String x = SemanticAnalizer.popStack();
String y = SemanticAnalizer.popStack();
String result = SemanticAnalizer.checkCube (x, y, operator );
SemanticAnalizer.pushStack(result);
twiceHere = false; /
/ reset the flag
}
2. Store the operator that
creates the loop?
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Parser
1. Store in a flag (operatorWasUSed):
Did the operator ‘-’ exist?
2.
if (operatorWasUsed)
String x = SemanticAnalizer.popStack();
String result = SemanticAnalizer.checkCube (x, “!” );
SemanticAnalizer.pushStack(result);
}
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Parser
1. Store in a flag (twiceHere):
Did we pass this point twice?
2.
if (twiceHere)
String x = SemanticAnalizer.popStack();
String y = SemanticAnalizer.popStack();
String result = SemanticAnalizer.checkCube (x, y, “&” );
SemanticAnalizer.pushStack(result);
twiceHere = false; /
/ reset the flag
}
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Parser
1. Store in a flag (twiceHere):
Did we pass this point twice?
2.
if (twiceHere)
String x = SemanticAnalizer.popStack();
String y = SemanticAnalizer.popStack();
String result = SemanticAnalizer.checkCube (x, y, “&” );
SemanticAnalizer.pushStack(result);
twiceHere = false; /
/ reset the flag
}
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Assignment 2 | Code
String x = SemanticAnalizer.popStack();
String y = SemanticAnalizer.popStack();
String result = SemanticAnalizer.checkCube (x, y, “=” );
if (!result.equals(“OK”) {
error(2);
}
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Homework
Programming
Final Version of Your Parser
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Extra
If time allows it
start with your Semantic Analyzer
(more details/work is coming)
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Questions
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Compilers
Javier Gonzalez-Sanchez, Ph.D.
jgonzalezs@up.edu.mx
Spring 2024
Copyright. These slides can only be used as study material for the Compilers course at Universidad Panamericana.
They cannot be distributed or used for another purpose.