EZGraphs
A graphs and charts generating language
Vincent Dobrev
Edlira Kumbarce
vd2006@columbia.edu
ek2248@columbia.edu
COMS W4115: Programming Languages and Translators
Spring 2007
Introduction
•
Why graphs?
Graphs are used widely. They communicate
information more easily and efficiently than
words or tables.
•
Objective
Provide a language that can be used to create
charts and graphs, targeting those with a little
prior programming experience.
Features
•
User-Friendly Syntax
Very similar to C and Java. Intuitive keywords
and internal function names. More organized than
Ploticus.
•
Easy Debugging
Non-cryptic and informative error messages
make it easy to use and debug. User given exact
location of error with file name and line and
column numbers.
Features (cont’d)
•
Portability
Based on Java, so it only depends on the
presence of the Java Runtime Environment.
•
Data Types & Operators
Supports boolean, integer, floating-point, and
string data types, as well as multi-dimensional
arrays.
Features
•
(cont’d)
File Inclusion
Allows code reuse and modularity. More
organized programs.
•
Control Flow Statements
Supports conditionals (if-then-else) and iterative
statements (loops), which in turn enable user to
create recursive functions.
Features (cont’d)
•
Pre-Defined Functions






Drawing: point(), line(), polygon(), etc.
Transfromation: translate(), scale(), shear() etc.
Data Acquiring: data()
Math: exp(), log(), pow(), sqrt(), etc.
Auxiliary: strToInt(), strToFloat(), substring(), size(), etc.
Output: print(), println() , save(), show()
Example 1 - Recursion
/*
* Sierpinski Triangle.
*/
void main() {
canvas(600, 600);
scale(1, -1);
translate(0, -600);
triangles(50, 50, 550, 50, 300, 550, 1);
show();
}
void triangles(int x1, int y1, int x2, int y2,
int x3, int y3, int level) {
line(x1, y1, x2, y2);
line(x2, y2, x3, y3);
line(x3, y3, x1, y1);
int
int
int
int
int
int
xp1
yp1
xp2
yp2
xp3
yp3
=
=
=
=
=
=
(x2+x1)
(y2+y1)
(x3+x2)
(y3+y2)
(x1+x3)
(y1+y3)
/
/
/
/
/
/
2;
2;
2;
2;
2;
2;
if (level < 8) {
triangles(x1, y1, xp1, yp1, xp3, yp3, level+1);
triangles(xp1, yp1, x2, y2, xp2, yp2, level+1);
triangles(xp3, yp3, xp2, yp2, x3, y3, level+1);
}
}
Example 2 - A Pie Chart
/*
* A pie chart illustrating distribution of income.
*/
void main() {
int fields = 7;
/* Colors. */
int[][] c = new int[fields][3];
c[0][0] = 255; c[0][1] = 50; c[0][2] = 0;
c[1][0] = 0;
c[1][1] = 255; c[1][2] = 0;
...
c[6][0] = 255; c[6][1] = 255; c[6][2] = 0;
/* Labels. */
string[] l = new string[fields];
l[0] = "Savings";
l[1] = "Insurance";
...
l[6] = "Housing";
/* Percentages. */
int[] p = new int[fields];
p[0] = 9;
p[1] = 11;
...
p[6] = 21;
...
Example 2 - A Pie Chart (cont’d)
canvas(400,400);
background(244,244,244);
string title = "Income Distribution";
font("Arial", 0, 20);
int width = width(title);
text(title, 200 - width/2, 40);
stroke(2);
line(50,50,350,50);
translate(100,100);
int start = 0, end = 0;
for (int i = 0; i < fields; i++) {
color(c[i][0],c[i][1],c[i][2]);
start += end;
end = p[i] * 360 / 100;
fillArc(0,0,200,200,start,end);
}
show();
}
Output:
Language Implementation
•
The source code is parsed and executed right
away with no intermediate code.
•
Programs reside in .ezg files, with one file
containing a main() function and any number of
other .ezg files containing other functions.
Language Implementation (cont’d)
•
Three types of output:
1. Text in the console
2. An image in a window on-screen
3. An image in a file
• Exception handling mechanism catches, formats,
and prints out error messages for the user.
Examples:
1.
2.
3.
4.
Error:
Error:
Error:
Error:
draw.ezg:48:10: expecting ID, found '=‘
draw.ezg:59:6: unexpected data type being assigned to array
recursion.ezg:5:5: function fact(int) expected to return int
recursion.ezg:7:16: variable g not declared
Architecture
.ezg
source
files
Lexer
Exception
Handler
Output
Tokens
Parser
EzgAST
Types
Walker
Front End
Interpreter
Back End
data
file
Interpreter Structure
EzgSymbolTable
EzgInterpreter
EzgFunction
EzgStringTokenizer
data
file
EzgInternalFunctions
Console Output
Screen Output (image)
EzgPainter
.png
(image)
Type System
Base type class
EzgArray
Type classes
EzgBool
EzgType
EzgFloat
EzgInt
EzgString
EzgVoid
Type Conversions & Operators
Type Conversions & Operators (cont’d)